Hi all,

Not having immediate success (but by no means having tapped out
all available vendors or sources yet, either) I have not yet found
suitable gears to feed the quick change gear box on the Hendey.

I did in the course of poking through some of my boxes come
across a 3"OD x 6" long hunk of 6061-T6 aluminum (aluminium for
those across the pond).

This is where the insanity comes in:

I have two 72T 14DP gears. If I had two 36T 14DP gears, I should
in theory be able to generate all the speeds I need for my gearbox.
If I had 3 or 4, I'd even have extras for idlers. These are 14.5 deg.
pressure angle gears. I also have a 90T gear to also use for idlers.

I've studied John Stevenson's document at
http://www.metalwebnews.com/howto/gear/gear1.html

and see he never posted data there for 14.5 deg. PA gears, though a
wander through Google Groups shows that he's supplied odd numbers
here and there for individual responses. Does anyone know of a
source for similar data to his "table 2" for 14.5 PA gears?

But his technique also got me thinking:

All I really need to create approximate gears is a form tool, it
doesn't have to be one for horizontal milling, be it disk type or
fly cutter type. Why not a single lip milling cutter, aka, form
ground D-bit? Glenn Ashmore just made a simple taper one for his
grinding fixture with apparent success. Probably grind one up out
of a broken tap or drill bit, and use the ultimate reference for
tooth form, one of the tooth spaces of the existing gears. Chuck
the bit of rod in a hand-held drill, and rotate it against the
grinding wheel. Once happy with the form as compared with the
master gear, grind off half to form the cutter.

Next, drill and bore my blank for 1", and turn to 2.571 OD. Not
likely I'll hit either exact, but hopefully well enough for this
exercise. And by doing them both in one set-up, I'll not be relying
on my decrepit 3-jaw for accuracy.

Once removed, mount the blank on a 1" arbor. Will probably use one
or both of a filed keyway and/or a tapped hole for a set screw (or
even 2?). Mount 1" arbor in boring bar holder, on center line, of
my 200 series tool post. On the other end, mount keyed 72T gear to
use as an index with an improvised locating pin. Use the boring bar
clamp to resist rotation and not put too much load on the pin.
Either buy or improvise an end mill holder (4MT), and mount the cutter
in the spindle. Set the blank axis at the proper final gear depth.
Set a feed stop. Feed the blank past the cutter with the crossfeed,
increasing infeed in several passes until I reach the stop for each
tooth space, then re-index.

The big advantage of this setup would be that it does not require
either a milling machine or a milling adapter for the lathe, just the
boring bar holder, and other pieces I already have on hand.

Possible pitfalls: Running out of crossfeed distance to finish across
the gearblank faces. Not having enough room to use the 72T gear
without it hitting the saddle as I infeed. Losing index and messing
up gear spacing, either by bending the locating pin or poor clamping
or rotating the index gear or the gear blank on the arbor. Mangling
or breaking the cutter with poor selection of milling feeds or speeds.
Trying to cut without noticing the cutter has become dull (how do you
resharpen a D-bit form cutter, anyway?). Mangling my cutter beyond
repair before I get all the blanks cut. Before I get any cut. Before
I get all the tooth spaces on one gear cut. Better to risk everything
and cut all the blanks at once? Or better to risk the cutting edge
dulling and cutting one blank at a time? Maybe one to learn on, then
the rest as a group? I should at least have enough stock for two or
three tries, depending on how many gears I want to end up with.
Given that I'll be cutting aluminum and not steel or cast iron, am I
likely to have sufficient rigidity and cutter life to complete this?
Any other obvious or not-so-obvious pitfalls I'm overlooking?

And last but not least, am I likely to run into problems running
6061 gears with cast iron gears in the gearbox feed train?

So give it to me straight, guys, how insane am I to even consider
this? I note that broken drill bits are essentially free, and the
chunk of 6061 cost me maybe $3 at a flea market. Have I mentioned
yet that this would be my first project on the lathe?

Thanks in advance,
--Glenn Lyford

"Glenn Lyford" wrote in message
7...

snip-----

Your idea should work, but you'll have to relieve the cutter if you want a
decent finish and expect the tool to go the distance. If you spin grind
the form, you'll have a cylinder of sorts that won't permit free cutting
because the entire form will be in contact. I think you can see that. Once
you've established the proper tooth form, and have removed half the
diameter, if you have steady hands you can grind relief up to the cutting
edge and hone the form afterwards with good results. You must then kill the
back half of the tool so only the forward rotating half makes contact. I've
done it for cutting gear teeth and for making corner rounding end mills with
excellent results. In essence, you end up with a single toothed form end
mill.

Don't use a drill shank, they are not hardened much past where the flutes
end. A broken tap is good, but they tend to be oversized, but you could
chuck it instead of use a collet or end mill holder of sorts.

If you have some type of device for holding your cutting tool, or intend to
buy or make one, why don't you consider buying a drill blank to make the
cutting tool? They're not very expensive and are of the highest quality,
heat treated and ground to size. The length you get with one could serve
to make more tools if you screw up. They are available in all the drill
sizes.

It might be smart to rough the entire blank close to size before going in
for finish cuts. That way if you do dull the tool, or otherwise make minor
mistakes, you will take the finish cuts with a sharp tool, with light cuts,
plus you can use pins to mike across the teeth to see if you are to proper
depth. It's almost always the best way to make anything in metal. Rough
first, then go back for finish cuts.

Great idea you have, but it might be a bit taxing of your ability if you
have little to no experience. No matter, just keep trying until you get it
right. What better way to learn?

Harold

In article , Harold & Susan Vordos says...

If you have some type of device for holding your cutting tool, or intend to
buy or make one, why don't you consider buying a drill blank to make the
cutting tool? They're not very expensive and are of the highest quality,
heat treated and ground to size. The length you get with one could serve
to make more tools if you screw up. They are available in all the drill
sizes.

Yes, a drill blank is the way to go. I had to replace
a 7mm shear pin in my snowblower, and they don't make
7mm shear pins! But they do make 7mm HSS drill blanks,
and I can attest to the fact that they come hard, and
tough, and don't cost much at all.

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

Your idea should work, but you'll have to relieve the cutter if you
want a decent finish and expect the tool to go the distance.

OK, that sounds like it should address a number of my concerns by
making my cutting tool more reliable... Would it be okay to leave
a short lip to allow for resharpenning, or am I actually after back
relief of the cutting edge for proper cutting geometry?

If you have some type of device for holding your cutting tool, or
intend to buy or make one, why don't you consider buying a drill blank
to make the cutting tool? They're not very expensive and are of the
highest quality, heat treated and ground to size.

Excellent idea. Also, if drill shanks aren't hardenned, would a
quench and temper to straw get me where I need to be? For a small
drill shank, I would think this should be possible with a propane
torch (don't have oxy-acet).

Rough first, then go back for finish cuts.

This sounds very sensible.

Great idea you have, but it might be a bit taxing of your ability if
you have little to no experience. No matter, just keep trying until
you get it right.

And little to lose except time and a few materials. OK,
and thanks for the sanity check! I'll be sure to get back
to everyone with my results, good or bad. If I don't get
too caught up in the project, I may even have pictures...

Probably won't have time to do this until after New Years,
so if anyone has other ideas, feel free to chime in.

--Glenn Lyford

Some time ago I worked out the math, but it showed some discrepancies with
John's table. I meant to ask him about them, but he was real busy at the
time, so I didn't.

By my figuring, you needed to figure;
the pitch radius of the gear from the standard formulas.
The base circle radius (from which the arc of the involutes is defined)
BCR = PR*cos(PA)
Then the tooth radius (radius of the form cutter)
TR = tan(PA)*BCR

I have a formula for the center to center spacing of the form cutters, but
it contains some scrawled additions, that I don't remember the logic behind.

I noticed the discrepancy with John's chart at this point and didn't figure
out the depth of feed.

John's system is ingenius, but unless you are in need of something with an
oddball pitch, it is hard to justify the amount of work involved.

A standard gear cutter will cost $30-$35 and, also be the right size to cut
a 37-47 tooth metric transposition set.

It would mean rethinking your setup.
I would find a smaller gear to use as an index (or hand cut a notched disk).
With the cutter mounted on an arbor chucked in the lathe
Then you set the blank horizontal, on center with the cutter and use the
cross feed to feed in to depth of cut on each tooth.
You will end up with a slightly concave tooth, but this will probably wear
in on the lathe in short order.

Paul K. Dickman

Glenn Lyford wrote in message ...
Hi all,

Not having immediate success (but by no means having tapped out
all available vendors or sources yet, either) I have not yet found
suitable gears to feed the quick change gear box on the Hendey.

I did in the course of poking through some of my boxes come
across a 3"OD x 6" long hunk of 6061-T6 aluminum (aluminium for
those across the pond).

This is where the insanity comes in:

I have two 72T 14DP gears. If I had two 36T 14DP gears, I should
in theory be able to generate all the speeds I need for my gearbox.
If I had 3 or 4, I'd even have extras for idlers. These are 14.5 deg.
pressure angle gears. I also have a 90T gear to also use for idlers.

I've studied John Stevenson's document at
http://www.metalwebnews.com/howto/gear/gear1.html

and see he never posted data there for 14.5 deg. PA gears, though a
wander through Google Groups shows that he's supplied odd numbers
here and there for individual responses. Does anyone know of a
source for similar data to his "table 2" for 14.5 PA gears?

But his technique also got me thinking:

All I really need to create approximate gears is a form tool, it
doesn't have to be one for horizontal milling, be it disk type or
fly cutter type. Why not a single lip milling cutter, aka, form
ground D-bit? Glenn Ashmore just made a simple taper one for his
grinding fixture with apparent success. Probably grind one up out
of a broken tap or drill bit, and use the ultimate reference for
tooth form, one of the tooth spaces of the existing gears. Chuck
the bit of rod in a hand-held drill, and rotate it against the
grinding wheel. Once happy with the form as compared with the
master gear, grind off half to form the cutter.

Next, drill and bore my blank for 1", and turn to 2.571 OD. Not
likely I'll hit either exact, but hopefully well enough for this
exercise. And by doing them both in one set-up, I'll not be relying
on my decrepit 3-jaw for accuracy.

Once removed, mount the blank on a 1" arbor. Will probably use one
or both of a filed keyway and/or a tapped hole for a set screw (or
even 2?). Mount 1" arbor in boring bar holder, on center line, of
my 200 series tool post. On the other end, mount keyed 72T gear to
use as an index with an improvised locating pin. Use the boring bar
clamp to resist rotation and not put too much load on the pin.
Either buy or improvise an end mill holder (4MT), and mount the cutter
in the spindle. Set the blank axis at the proper final gear depth.
Set a feed stop. Feed the blank past the cutter with the crossfeed,
increasing infeed in several passes until I reach the stop for each
tooth space, then re-index.

The big advantage of this setup would be that it does not require
either a milling machine or a milling adapter for the lathe, just the
boring bar holder, and other pieces I already have on hand.

Possible pitfalls: Running out of crossfeed distance to finish across
the gearblank faces. Not having enough room to use the 72T gear
without it hitting the saddle as I infeed. Losing index and messing
up gear spacing, either by bending the locating pin or poor clamping
or rotating the index gear or the gear blank on the arbor. Mangling
or breaking the cutter with poor selection of milling feeds or speeds.
Trying to cut without noticing the cutter has become dull (how do you
resharpen a D-bit form cutter, anyway?). Mangling my cutter beyond
repair before I get all the blanks cut. Before I get any cut. Before
I get all the tooth spaces on one gear cut. Better to risk everything
and cut all the blanks at once? Or better to risk the cutting edge
dulling and cutting one blank at a time? Maybe one to learn on, then
the rest as a group? I should at least have enough stock for two or
three tries, depending on how many gears I want to end up with.
Given that I'll be cutting aluminum and not steel or cast iron, am I
likely to have sufficient rigidity and cutter life to complete this?
Any other obvious or not-so-obvious pitfalls I'm overlooking?

And last but not least, am I likely to run into problems running
6061 gears with cast iron gears in the gearbox feed train?

So give it to me straight, guys, how insane am I to even consider
this? I note that broken drill bits are essentially free, and the
chunk of 6061 cost me maybe $3 at a flea market. Have I mentioned
yet that this would be my first project on the lathe?

Thanks in advance,
--Glenn Lyford

On 21 Dec 2003 07:08:33 -0800, jim rozen
wrote:


I had to replace
a 7mm shear pin in my snowblower, and they don't make
7mm shear pins! But they do make 7mm HSS drill blanks,
and I can attest to the fact that they come hard, and
tough, and don't cost much at all.

Oops. Shear pins are *supposed* to shear when something gets jammed,
rather than break something more expensive. In snowblowers they're
usually just mild steel. A 7 mm bolt might fit.

By my figuring, you needed to figure;
the pitch radius of the gear from the standard formulas.
The base circle radius (from which the arc of the involutes is
defined)
BCR = PR*cos(PA)
Then the tooth radius (radius of the form cutter)
TR = tan(PA)*BCR

I have a formula for the center to center spacing of the form cutters,
but it contains some scrawled additions, that I don't remember the
logic behind.

John's system is ingenius, but unless you are in need of something
with an oddball pitch, it is hard to justify the amount of work
involved.

Unfortunately, when the lathe was made, the standard seemed to be
even diametral pitches within this size range. The new standard
is 20-18-16-12-10..., so finding 14 DP gear cutters is problematic.
Of course, there's nothing to say that I need to keep using this
pitch of gear, either. I could conceivably use any pitch between
about 18 and 10, as long as I had enough gears to do the entire
train, and had enough meat to bore the hubs to 1" ID (the shaft
size at both the spindle output and quick change input).

Then you set the blank horizontal, on center with the cutter and use
the cross feed to feed in to depth of cut on each tooth.

That gets around having to use a milling attachment, at least.
Thanks.

--Glenn Lyford

http://www.mcmaster.com/asp/DisplCtl...CtlgPgNbr=2333

Paul K. Dickman


Glenn Lyford wrote in message ...
Unfortunately, when the lathe was made, the standard seemed to be
even diametral pitches within this size range. The new standard
is 20-18-16-12-10..., so finding 14 DP gear cutters is problematic.
Of course, there's nothing to say that I need to keep using this
pitch of gear, either. I could conceivably use any pitch between
about 18 and 10, as long as I had enough gears to do the entire
train, and had enough meat to bore the hubs to 1" ID (the shaft
size at both the spindle output and quick change input).

Then you set the blank horizontal, on center with the cutter and use
the cross feed to feed in to depth of cut on each tooth.

That gets around having to use a milling attachment, at least.
Thanks.

--Glenn Lyford

"Don Foreman" wrote in message
...
On 21 Dec 2003 07:08:33 -0800, jim rozen
wrote:


I had to replace
a 7mm shear pin in my snowblower, and they don't make
7mm shear pins! But they do make 7mm HSS drill blanks,
and I can attest to the fact that they come hard, and
tough, and don't cost much at all.

Oops. Shear pins are *supposed* to shear when something gets jammed,
rather than break something more expensive. In snowblowers they're
usually just mild steel. A 7 mm bolt might fit.

Yep! That drill blank, in this instance, could get pretty expensive, Jim!
I think I'd go with a soft 7 mm bolt, or get the dust knocked off the SB and
make a proper pin from mild steel.

Sure don't miss the snow we used to get in Utah. We get it here, but not
nearly as much, nor does it linger. Often gone within 24 hours. That's
my idea of winter!

Harold

"Glenn Lyford" wrote in message
7...
Your idea should work, but you'll have to relieve the cutter if you
want a decent finish and expect the tool to go the distance.

OK, that sounds like it should address a number of my concerns by
making my cutting tool more reliable... Would it be okay to leave
a short lip to allow for resharpenning, or am I actually after back
relief of the cutting edge for proper cutting geometry?

Anything less than a relief right to the cutting edge will drag, it's a
matter of degree. As it narrows, the effort to make the cut will decrease,
but the finish won't improve until there is no contact without relief.
In order for end mills to have proper relief and still have strength at the
cutting edge, you'll notice that they have a primary and secondary relief
ground on them to accommodate the radius of the cutter. It gets all the
more critical as the cutter decreases in diameter, so you'll have the very
best results if you relieve right to the cutting edge. That means that any
alteration to the tool that effects the centerline will have a corresponding
effect on the form of the tool, and even the rake angle. In spite of the
fact that you haven't changed the angle as it relates to the centerline of
the tool, if starts going positive at the point of contact with the part,
albeit in a minor way. That would have a corresponding minor effect on the
form, though probably not important enough to lose any sleep worrying about
the degree of error. You're likely to have more error in the tool from
grinding. My last attempt at this, although with a fly cutter instead,
was a year ago, and a check by comparator after grinding showed I'd ground
the form within a thou of what I desired. That was grinding by hand, using
a gear for the template, just as you will do.

If you have some type of device for holding your cutting tool, or
intend to buy or make one, why don't you consider buying a drill blank
to make the cutting tool? They're not very expensive and are of the
highest quality, heat treated and ground to size.

Excellent idea. Also, if drill shanks aren't hardenned, would a
quench and temper to straw get me where I need to be? For a small
drill shank, I would think this should be possible with a propane
torch (don't have oxy-acet).

Yes, you might be able to do that, but remember you're likely hardening HSS,
not simple carbon steel. How it reacts to torch hardening may or may not
be the same. I'm not well versed in heat treat, for the work I did in my
years in the shop was primarily done under government defense contract, so
everything, including heat treat, had to be done by certified facilities.
Therefore, except for custom tools made at the spur of the moment for my own
use, all was sub-contracted. You get familiar with designations, but not
procedures.

The work you'll do in getting this form correct won't be easy. It would
likely be a good investment to go with a drill blank instead. My guess is
your local tool supply house can sell you a 1/4" one for about $2. It'd be
a damned shame to get the form right after spending an hour (or more) on the
tool, only to have it chip on the first pass from improper heat treat.
That's one of the risks of heat treating by torch. On the other hand, if
it's the experience of doing the work that you desire, again, go for it.
What have you got to lose? You'll gain knowledge in the process, win or
lose.

Rough first, then go back for finish cuts.

This sounds very sensible.

Great idea you have, but it might be a bit taxing of your ability if
you have little to no experience. No matter, just keep trying until
you get it right.

And little to lose except time and a few materials.

Exactly. We all pay for our educations, it's a matter of how.

OK,
and thanks for the sanity check! I'll be sure to get back
to everyone with my results, good or bad. If I don't get
too caught up in the project, I may even have pictures...

Sounds good. I'm of the opinion that if you can grind a tool that is free
machining, you'll do a grand job of it. You've already done the majority
of the work in your head and seem to understand what's involved.

You might consider using either leaded steel or some 7075-T6 aluminum for
this project. Both machine very well, and would likely have the ability
to run with the other gears without problems.

Harold

"Paul K. Dickman" wrote in
:

http://www.mcmaster.com/asp/DisplCtl...LOG&CtlgPgNbr=
2333

Interesting. This will take more thought... That'd be cheaper
than buying new gears, at least.
--Glenn Lyford

In article , Don Foreman says...

Oops. Shear pins are *supposed* to shear when something gets jammed,
rather than break something more expensive. In snowblowers they're
usually just mild steel. A 7 mm bolt might fit.

Not *really* a shear pin, the drive for the wheels
is from a pinion gear on the output shaft of a
hydrostatic transmission. The small pinion drives
a larger gear, and that gear drives the solid
axle.

The axle has a hole in it, through which a 7mm dia
pin is pressed. The ends of the short pin protrude
about 1/4 inch on each side, and index into slots
in the gear's hub.

Honda made the pin a tight press fit into the axle,
and it's as hard as the piece of drill rod I replaced
it with. I think they wanted that to be the ultimate
fail point for the drive, and it did so by shearing
both ends off, leaving the stub in the axle.

I did a lot of soul-searching, and was going to put
a soft piece of steel, turned to size, back in its
place. But then I figured that the honda engineers
knew their stuff, so I bought the drill blank.

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

On 21 Dec 2003 07:08:33 -0800, jim rozen wrote:
Yes, a drill blank is the way to go. I had to replace
a 7mm shear pin in my snowblower, and they don't make
7mm shear pins! But they do make 7mm HSS drill blanks,
and I can attest to the fact that they come hard, and
tough, and don't cost much at all.

Bad idea to use a drill blank as a *shear* pin. It is supposed
to fail when there is an overload (think mechanical fuse).
Using a tougher higher tensile material is like putting a penny
behind the fuse in a fusebox.

Gary

Glenn Lyford wrote:
Hi all,

Not having immediate success (but by no means having tapped out
all available vendors or sources yet, either) I have not yet found
suitable gears to feed the quick change gear box on the Hendey.

I did in the course of poking through some of my boxes come
across a 3"OD x 6" long hunk of 6061-T6 aluminum (aluminium for
those across the pond).

I think this is your only mistake. Don't bother to make gears for
anything that is turned under power from aluminum. Gearing a
hand-operated knob that moves a valve will probably work with
aluminum gears, but the change gears in the lathe can transmit
considerable torque on coarse threads. If they don't break off,
they are going to wear really fast.

Jon

In article , Gary Coffman says...

Bad idea to use a drill blank as a *shear* pin. It is supposed
to fail when there is an overload (think mechanical fuse).
Using a tougher higher tensile material is like putting a penny
behind the fuse in a fusebox.

Except for the fact that this is effectively what
Honda put in that spot. Real hard, real tough
material. Maybe the term 'shear' is wrong for
the description.

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

Glenn Lyford wrote in message . 17...
"Paul K. Dickman" wrote in
:

http://www.mcmaster.com/asp/DisplCtl...LOG&CtlgPgNbr=
2333

Interesting. This will take more thought... That'd be cheaper
than buying new gears, at least.
--Glenn Lyford

You can buy this same gear cutter from Wholesale tool for $27. If you
want to make your own cutter refer to Ivan Law's book on gearcutting.
It appears to be the basis for John Stevenson's article on this
subject.

Gearing a hand-operated knob that moves a valve will probably
work with aluminum gears, but the change gears in the lathe can
transmit considerable torque on coarse threads. If they don't
break off, they are going to wear really fast.

All the more reason to try it first with aluminum, then,
to get a feel for it before making a "real" set. I'm not
likely to make power feed cuts at the capacity of the
machine anytime soon, at least not knowingly. I'm hoping
that when nicer weather rolls around, I'll have found
"real" gears anyway, so I'm hoping this isn't a permanent
solution.

Someone else suggested 12L14, which also sounds eminently
sensible... maybe I can get it and the drill blank at the
same time.

--Glenn Lyford

In article ,
Glenn Lyford wrote:
Hi all,

Not having immediate success (but by no means having tapped out
all available vendors or sources yet, either) I have not yet found
suitable gears to feed the quick change gear box on the Hendey.

It has been several days since you posted this, and I have until
now only seen the followups, not the original.

I did in the course of poking through some of my boxes come
across a 3"OD x 6" long hunk of 6061-T6 aluminum (aluminium for
those across the pond).

This is where the insanity comes in:

I have two 72T 14DP gears. If I had two 36T 14DP gears, I should
in theory be able to generate all the speeds I need for my gearbox.
If I had 3 or 4, I'd even have extras for idlers. These are 14.5 deg.
pressure angle gears. I also have a 90T gear to also use for idlers.

Hmm ... before I get into the rest of this -- note that the
formed gear tooth cutters are available from places like MSC for fairly
reasonable prices. For example, I have just completed my set of 16 DP
14.5 Degree Pressure angle cutters -- buying two at a time, for the gear
pitch used in my Clausing 12x24" lathe. The ones which I got were
selling for $23.62 each -- and most of them were made in China, but
appear to be good milling cutters.

[ ... ]

All I really need to create approximate gears is a form tool, it
doesn't have to be one for horizontal milling, be it disk type or
fly cutter type. Why not a single lip milling cutter, aka, form
ground D-bit?

I'm not sure how well such would work, but it would be an
interesting experiment. It would probably work better in the aluminum
than it would in a proper material for the gears. (I'll go into that
more somewhat later in this followup.)

Glenn Ashmore just made a simple taper one for his
grinding fixture with apparent success. Probably grind one up out
of a broken tap or drill bit, and use the ultimate reference for
tooth form, one of the tooth spaces of the existing gears.

Note that ideally, the tooth form varies with the number of
teeth on the gear, so you should use a gear which already has the proper
number of teeth as the reference. The gear tooth cutters in the set are
split into eight to cover the whole of the range of reasonable
teeth, with the ones with smaller numbers of teeth covering the smallest
range of tooth counts, as the shapes change more rapidly with the lower
number of teeth.

Chuck
the bit of rod in a hand-held drill, and rotate it against the
grinding wheel. Once happy with the form as compared with the
master gear, grind off half to form the cutter.

As others have mentioned, -- what about forming the relief on
the cutter's form?

Next, drill and bore my blank for 1", and turn to 2.571 OD. Not
likely I'll hit either exact, but hopefully well enough for this
exercise. And by doing them both in one set-up, I'll not be relying
on my decrepit 3-jaw for accuracy.

Agreed.

Once removed, mount the blank on a 1" arbor. Will probably use one
or both of a filed keyway and/or a tapped hole for a set screw (or
even 2?). Mount 1" arbor in boring bar holder, on center line, of
my 200 series tool post. On the other end, mount keyed 72T gear to
use as an index with an improvised locating pin. Use the boring bar
clamp to resist rotation and not put too much load on the pin.

This is not bad -- but a modification of this could mount the
axis of the gear either vertical (with the reference gear above the
workpiece -- but this would require a vertical slide -- e.g. a milling
adaptor for the lathe), or horizontal, with the axis above the spindle's
axis to clear the cross-slide, which would allow the cross-feed to be
used to feed the blank through the intersection with the cutter --
either a standard gear tooth mill, or a fly cutter with a form ground
tooth profile. (Hmm ... you would still need a vertical feed to adjust
the depth of cut.

I presume that you will be skipping every other tooth on the 72
tooth master. I would suggest that you fill alternate teeth with layout
blue before you start, so you can identify which ones to use for
indexing.

Either buy or improvise an end mill holder (4MT), and mount the cutter
in the spindle.

An MT-4 blank should be large enough to machine a step and a 1"
diameter to hold the gear cutter -- if you use a gear tooth mill for the
purpose.

Set the blank axis at the proper final gear depth.
Set a feed stop. Feed the blank past the cutter with the crossfeed,
increasing infeed in several passes until I reach the stop for each
tooth space, then re-index.

Reasonable. Ideally with a keyway to lock both the workpiece
and the reference gear in place -- which you already mentioned as a
possibility.

The big advantage of this setup would be that it does not require
either a milling machine or a milling adapter for the lathe, just the
boring bar holder, and other pieces I already have on hand.

Plus some adaptation of the boring bar holder to allow mounting
of the index pin holder.

Possible pitfalls: Running out of crossfeed distance to finish across
the gearblank faces. Not having enough room to use the 72T gear
without it hitting the saddle as I infeed.

How long are you planning to make the shaft? You could make it
long enough to put the reference gear far out of the way (at some
tradeoff of rigidity.

Losing index and messing
up gear spacing,

Hence the need for the keys on both gears -- and the suggestion
of layout dye to identify which teeth you are allowed to use as index
references.

either by bending the locating pin or poor clamping
or rotating the index gear or the gear blank on the arbor.

Turn the nose of the index pin to the tooth form, so it offers
the maximum contact while milling. Harden and temper it to reduce the
chance of deformation during cutting stresses. (Or use a section of
rack gear of the right pitch mounted to the nose of the pin so you have
lots of contact surface.)

Use keys on both the reference gear and the workpiece.

Mangling
or breaking the cutter with poor selection of milling feeds or speeds.

This may be the greatest problem -- along with chips causing the
cut to be oversized, since the D-form will not spend enough time clear
of the cut to keep the chips out of the game.

Trying to cut without noticing the cutter has become dull (how do you
resharpen a D-bit form cutter, anyway?).

At a guess -- start out with the remaining material covering 200
degrees or so, with radial lines in to the center. Sharpen by grinding
back the leading edge.

Mangling my cutter beyond
repair before I get all the blanks cut.

If you consider this to be a likely problem, make more than one
before you start. Probably not a problem in 6061, but I suspect that
you will have more problems with a reasonable material for the gears.

Before I get any cut. Before
I get all the tooth spaces on one gear cut. Better to risk everything
and cut all the blanks at once? Or better to risk the cutting edge
dulling and cutting one blank at a time?

Since the life of the cutter is in question, do one at a time,
so you minimize the number of blanks you mess up if something does go
wrong. (If you were making these with standard tooling, on a standard
machine, there would be a good argument for making them in a group, of
course.)

Maybe one to learn on, then
the rest as a group?

Based on the luck with the cutter on the first?

You'll want something like kerosene, or WD-40 as a cutting
lubricant when cutting aluminum. For other materials, you will want to
change the lubricant as appropriate.

I should at least have enough stock for two or
three tries, depending on how many gears I want to end up with.
Given that I'll be cutting aluminum and not steel or cast iron, am I
likely to have sufficient rigidity and cutter life to complete this?

Probably -- but I don't think that you really *want* to make
that many gears.

Any other obvious or not-so-obvious pitfalls I'm overlooking?

And last but not least, am I likely to run into problems running
6061 gears with cast iron gears in the gearbox feed train?

Yes -- the aluminum is too soft (even the 6061T6) to operate
meshing with cast iron or steel gears at the power loads in a threading
geartrain, and you will wind up with the aluminum transferring onto the
steel or cast iron gears, making them a poorer fit to other proper
gears.

You may want to *try* the first gears with 6061 and test them
for fit -- but not use them for any cutting. Once you have done this,
you can even switch to one of the aluminum ones for the reference gear,
and thus eliminate the problem of accidentally not skipping the right
number of teeth. (But this means that you will need the pin to be
adjustable to handle the different radii of the two gear sizes.)

So give it to me straight, guys, how insane am I to even consider
this? I note that broken drill bits are essentially free, and the
chunk of 6061 cost me maybe $3 at a flea market.

As others have mentioned -- the broken drill bits are not
hardened in the shanks, which is where you would find the proper
starting shape for forming your D-cutter (if that is what you feel you
must use. I'm not sure, but I *think* that drill bits may even be two
part, with the flutes being HSS, and the shank mild steel. As others
have suggested, drill rod is inexpensive (36" lengths), and can be
nicely hardened after turning to near shape. You then grind to final
dimension, since the hardening process usually introduces some
distortion.

Have I mentioned
yet that this would be my first project on the lathe?

This makes it an ambitious learning experience.

Best of luck,
DoN.
--
Email: | Voice (all times): (703) 938-4564
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--- Black Holes are where God is dividing by zero ---

"DoN. Nichols" wrote in message
...
big snip---

I'm not sure, but I *think* that drill bits may even be two
part, with the flutes being HSS, and the shank mild steel.

They have that appearance, but they are induction hardened, so there is a
very distinguishing line where heating and hardening ends due to the rapid
heating. The entire drill should be the same material.

Harold

On Sun, 21 Dec 2003 04:18:14 GMT, Glenn Lyford
wrote:

Hi all,

Not having immediate success (but by no means having tapped out
all available vendors or sources yet, either) I have not yet found
suitable gears to feed the quick change gear box on the Hendey.

I did in the course of poking through some of my boxes come
across a 3"OD x 6" long hunk of 6061-T6 aluminum (aluminium for
those across the pond).

This is where the insanity comes in:

I have two 72T 14DP gears. If I had two 36T 14DP gears, I should
in theory be able to generate all the speeds I need for my gearbox.
If I had 3 or 4, I'd even have extras for idlers. These are 14.5 deg.
pressure angle gears. I also have a 90T gear to also use for idlers.

I've studied John Stevenson's document at
http://www.metalwebnews.com/howto/gear/gear1.html

and see he never posted data there for 14.5 deg. PA gears, though a
wander through Google Groups shows that he's supplied odd numbers
here and there for individual responses. Does anyone know of a
source for similar data to his "table 2" for 14.5 PA gears?

But his technique also got me thinking:

All I really need to create approximate gears is a form tool, it
doesn't have to be one for horizontal milling, be it disk type or
fly cutter type. Why not a single lip milling cutter, aka, form
ground D-bit? Glenn Ashmore just made a simple taper one for his
grinding fixture with apparent success. Probably grind one up out
of a broken tap or drill bit, and use the ultimate reference for
tooth form, one of the tooth spaces of the existing gears. Chuck
the bit of rod in a hand-held drill, and rotate it against the
grinding wheel. Once happy with the form as compared with the
master gear, grind off half to form the cutter.

Next, drill and bore my blank for 1", and turn to 2.571 OD. Not
likely I'll hit either exact, but hopefully well enough for this
exercise. And by doing them both in one set-up, I'll not be relying
on my decrepit 3-jaw for accuracy.

Once removed, mount the blank on a 1" arbor. Will probably use one
or both of a filed keyway and/or a tapped hole for a set screw (or
even 2?). Mount 1" arbor in boring bar holder, on center line, of
my 200 series tool post. On the other end, mount keyed 72T gear to
use as an index with an improvised locating pin. Use the boring bar
clamp to resist rotation and not put too much load on the pin.
Either buy or improvise an end mill holder (4MT), and mount the cutter
in the spindle. Set the blank axis at the proper final gear depth.
Set a feed stop. Feed the blank past the cutter with the crossfeed,
increasing infeed in several passes until I reach the stop for each
tooth space, then re-index.

The big advantage of this setup would be that it does not require
either a milling machine or a milling adapter for the lathe, just the
boring bar holder, and other pieces I already have on hand.

Possible pitfalls: Running out of crossfeed distance to finish across
the gearblank faces. Not having enough room to use the 72T gear
without it hitting the saddle as I infeed. Losing index and messing
up gear spacing, either by bending the locating pin or poor clamping
or rotating the index gear or the gear blank on the arbor. Mangling
or breaking the cutter with poor selection of milling feeds or speeds.
Trying to cut without noticing the cutter has become dull (how do you
resharpen a D-bit form cutter, anyway?). Mangling my cutter beyond
repair before I get all the blanks cut. Before I get any cut. Before
I get all the tooth spaces on one gear cut. Better to risk everything
and cut all the blanks at once? Or better to risk the cutting edge
dulling and cutting one blank at a time? Maybe one to learn on, then
the rest as a group? I should at least have enough stock for two or
three tries, depending on how many gears I want to end up with.
Given that I'll be cutting aluminum and not steel or cast iron, am I
likely to have sufficient rigidity and cutter life to complete this?
Any other obvious or not-so-obvious pitfalls I'm overlooking?

And last but not least, am I likely to run into problems running
6061 gears with cast iron gears in the gearbox feed train?

So give it to me straight, guys, how insane am I to even consider
this? I note that broken drill bits are essentially free, and the
chunk of 6061 cost me maybe $3 at a flea market. Have I mentioned
yet that this would be my first project on the lathe?

Thanks in advance,


The D bit method of cutting gears works fine. I've cut quite a few by
this method - mostly in hard light alloy and and in tufnol (resin
impregnated stacked sheets of linen cloth) together with a few in cast
iron. The method also works well for cutting timing belt sprockets.

I see no problem in using light alloy change gears in a home
workshop lathe. A quick check using a handwheel to traverse the
carriage by the leadscrew shows clearly that the loads on
changewheels are extremely light - even when taking heavy cuts!

The choice of changewheel DP is mainly controlled, not by load
carrying capacity, but by the desire to bridge the large gap between
spindle and lead screw without using wheels with excessively large
numbers of teeth. I've happily utilised a pair of brass 32DP wheels as
part of a non standard change wheel train without problem!

Don't mess about trying to grind HSS for the bits - it's so much
easier to turn carbon steel drill rod to the right profile in its soft
state in the lathe and then flame harden it. Heat to bright red,
quench and then temper to light straw (just beginning to develop a
yellow oxide film) and it will be fine for the fairly small number of
gears that you intend to cut.

Life is much easier if you first hog out most of the tooth
spaces with a roughing cutter and save your carefully profiled D bit
for the finishing cut. The roughing cutter can be an end mill or a
slitting saw no wider than the width of the bottom of the tooth space.
If these aren't to hand make up a second D bit - don't bother to
profile this cutter just make it as a simple taper cutter because it's
so much easier to sharpen. 29 deg (30 deg is near enough!) included
angle for 14 1/2 deg pressure angle gears.

If you go the taper cutter route the small end should taper to
slighly less diameter than the width of the bottom of the tooth space.
The end should not be square to the cutter axis but:-

Tilted in about 5 deg so that only the outer tip cuts

Tilted back about 10 deg so that there is positive cutting clearance
for the rounded part of the end so that itdoes not rub against the
workpiece.

These two angles are simultaneously achieved by holding the cutter
against the grinding wheel at the correct angle - first tilt it in a
bit and then down a bit. The angles are are not critical even half or
twice as much is OK. The important thing is that neither should be
zero.

The remaining problem is cutting clearance for the side of the
D bits. For the roughing cutter, cautiously grind in just below the
cutting edge at about 10 deg clearance angle until the ground face
just reaches the cutting edge. Then heavily grind the remaining
untouched surface so that no part is as high as the cutting edge.

For fine cuts it is possible to use the finishing cutter without
any side clearance - this is the way that D bit taper reamers work.
However the cutting geometry is extremely poor - it's pushing the
metal away rather than cutting. On the other hand it's pretty
difficult to grind cutting clearance right to the cutting edge of form
tools without accidentally damaging the form shape. The usual
compromise which works pretty well is to grind in the same way as for
the roughing tool but stop grinding just before the grind reaches the
cutting edge - ideally leaving an untouched land about 10 thou wide
below the cutting edge.

Good Luck!

Jim

In article ,
Harold & Susan Vordos wrote:

"DoN. Nichols" wrote in message
...
big snip---

I'm not sure, but I *think* that drill bits may even be two
part, with the flutes being HSS, and the shank mild steel.

They have that appearance, but they are induction hardened, so there is a
very distinguishing line where heating and hardening ends due to the rapid
heating. The entire drill should be the same material.

O.K. That explains the differing hardness. I wasn't sure how
soft HSS could be made, which is why I was speculating the two-piece
construction.

Thanks,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article ,
says...

Don't mess about trying to grind HSS for the bits - it's so much
easier to turn carbon steel drill rod to the right profile in its soft
state in the lathe and then flame harden it.

Hmm. So you initially use a lathe to turn a *round*
part, with the correct taper shape to just fit inside
the space between the gear teeth, and then remove
about half of it to make the fly cutter?

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

"DoN. Nichols" wrote in message
...
In article ,
Harold & Susan Vordos wrote:

"DoN. Nichols" wrote in message
...
big snip---

I'm not sure, but I *think* that drill bits may even be two
part, with the flutes being HSS, and the shank mild steel.

They have that appearance, but they are induction hardened, so there is a
very distinguishing line where heating and hardening ends due to the
rapid
heating. The entire drill should be the same material.

O.K. That explains the differing hardness. I wasn't sure how
soft HSS could be made, which is why I was speculating the two-piece
construction.

Thanks,
DoN.

While I'm not privy to the exact speed at which the shanks get heated, I
can relate one personal experience, that of watching a splined shaft for an
armored personnel carrier getting heat treated by induction heating. The
shaft, about 1-1/4" diameter, was placed within the induction coil and went
from ambient temp to quench temperature in something like 20 seconds. That
is, of course, a function of the power of the induction power supply. The
larger (more powerful) the unit, the faster the heating. Typically, the
heating occurs at such a fast rate that there is precious little travel of
the heated area(s). It's not uncommon for heating coils to heat specific
areas of items, leaving the balance of the article it its original state.
Induction heating is really a great way to go, although rather expensive to
set up initially.

Harold

In article ,
jim rozen wrote:
In article ,
says...

Don't mess about trying to grind HSS for the bits - it's so much
easier to turn carbon steel drill rod to the right profile in its soft
state in the lathe and then flame harden it.

Hmm. So you initially use a lathe to turn a *round*
part, with the correct taper shape to just fit inside
the space between the gear teeth, and then remove
about half of it to make the fly cutter?

Except that he is not making a fly cutter, but rather a
D-profile milling cutter (somewhat akin to a D-profile reamer.) There,
the round starting shape is needed.

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article ,
Harold & Susan Vordos wrote:

"DoN. Nichols" wrote in message
...
In article ,
Harold & Susan Vordos wrote:

[ ... ]

They have that appearance, but they are induction hardened, so there is a
very distinguishing line where heating and hardening ends due to the
rapid
heating. The entire drill should be the same material.

O.K. That explains the differing hardness. I wasn't sure how
soft HSS could be made, which is why I was speculating the two-piece
construction.

[ ... ]

While I'm not privy to the exact speed at which the shanks get heated, I
can relate one personal experience, that of watching a splined shaft for an
armored personnel carrier getting heat treated by induction heating. The
shaft, about 1-1/4" diameter, was placed within the induction coil and went
from ambient temp to quench temperature in something like 20 seconds. That
is, of course, a function of the power of the induction power supply. The
larger (more powerful) the unit, the faster the heating. Typically, the
heating occurs at such a fast rate that there is precious little travel of
the heated area(s). It's not uncommon for heating coils to heat specific
areas of items, leaving the balance of the article it its original state.
Induction heating is really a great way to go, although rather expensive to
set up initially.

And they also require quite a bit of power -- even though the
vast bulk of it goes directly into the workpiece, it still takes quite a
bit of current to raise the temperature of that much material that
quickly.

It is certainly beyond the power budget here at home. :-)

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article , DoN. Nichols says...

Hmm. So you initially use a lathe to turn a *round*
part, with the correct taper shape to just fit inside
the space between the gear teeth, and then remove
about half of it to make the fly cutter?

Except that he is not making a fly cutter, but rather a
D-profile milling cutter (somewhat akin to a D-profile reamer.) There,
the round starting shape is needed.

OK, a single tooth end mill so to speak. But it's
a cutter that is effectively run the same way a fly
cutter is. I could imagine forming the tool from
a square blank of HSS if one could offhand form grind
the profile correctly.

The idea of using a *round* tool that is then half
ground away (with suitable relief added) makes a lot
of sense, as it's easier to profile the tooth form
using a lathe tool, in the round, than it would be
to create the same form tool offhand from, say,
a HSS square blank, using a pedestal grinder.

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

Hi Jim,

This is one of several standard ways to make gear cutters for clock and
watch work. You can make an offset mandrel to allow the turning, then
remove a section of the disc. Another option is to drill a smaller hole
to secure the cutter for turning, then enlarge the hole with some offset
to provide clearance. When mounted on a standard arbor there is
sufficient clearance all around. For brass there is no rake, so you can
restone the cutting surface quite a few times before the cutter is too
far gone to use.

At least one guy slices four cutters from each disk, and mounts then in
a slot on the face of his cutter holder. Quite a few ways to skin this
cat when simply turning the profile on a bit of drill rod and then
grinding a D style cutter isn't quite good enough.

Here's a link with a photo of a commercially made gear cutter in this style:

http://www.clock-keys.com/pdf/116.PDF

And some sharper pictures of similar ones at:

http://www.timekeepersworkbench.com/cutters/

A slightly fancier version (four cutting teeth) is described at:

http://www.metalwebnews.com/howto/gear/gear1.html

Seems there's a few sets of online instructions floating around for
making single and multiple tooth cutters, but I'll be darned if I can
find the all of the links right now, maybe a DNS down somewhere. John
Shadle has some really good instructions on combining the flycutter
style with the turned form disk approach. The link to the articles
(which are in Word format) is:

http://onlineclockbuilding.com/download.html

If you are interested in clocks, check out the rest of John's site, he
does some very neat stuff.

Neat little gadgets, not sure I'd try to cut a 4DP with one, but very
effective in clock and watch sizes anyhow. You do have to do a bit more
to generate the correct shape for low tooth count gears, such as
pinions, but for the usual 30+ tooth count clock wheels these work
nicely. In clock work you are gearing up be large amounts, rather than
gearing down as we usually do in machine tools. The tooth form is
usually cycloidal or a variation as lower friction is more important
than power transfer in clocks and watches.

Cheers,
Stan

jim rozen wrote:

In article ,
says...


Don't mess about trying to grind HSS for the bits - it's so much
easier to turn carbon steel drill rod to the right profile in its soft
state in the lathe and then flame harden it.


Hmm. So you initially use a lathe to turn a *round*
part, with the correct taper shape to just fit inside
the space between the gear teeth, and then remove
about half of it to make the fly cutter?

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

SNIP

While I'm not privy to the exact speed at which the shanks get heated, I
can relate one personal experience, that of watching a splined shaft for an
armored personnel carrier getting heat treated by induction heating. The
shaft, about 1-1/4" diameter, was placed within the induction coil and went
from ambient temp to quench temperature in something like 20 seconds. That
is, of course, a function of the power of the induction power supply. The
larger (more powerful) the unit, the faster the heating. Typically, the
heating occurs at such a fast rate that there is precious little travel of
the heated area(s). It's not uncommon for heating coils to heat specific
areas of items, leaving the balance of the article it its original state.
Induction heating is really a great way to go, although rather expensive to
set up initially.

Harold

Hey Harold,

I've seen timing gears for General Motors V-8 engines done in the same
sort of time span. The raw stock is hobbed and bored in a continuous
length from 22' octagonal bar stock, and then parted off to thickness
and including a chamfer. The cut gear form is then individually
heated and quenched, while the bore for the cam shaft is left
relatively soft so that the key-way can be broached. I think they are
then ground for finish after that operation, but I don't recall
exactly. Fascinating to watch.

I've also seen clothes washer shafts silver-brazed very fast with
localized induction. Very fast. Neat.

Take care.

Brian Lawson,
Bothwell, Ontario.