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(in
) said:

| Morris Dovey wrote:
|| (in
|| ) said:
||
||| Hi all,
|||
||| I have an upcoming project that's still in the "thinking stage",
||| which is to say that I'm trying yo figure out all of the
||| operations that I'll need to do and finding ways to do it with my
||| existing skills and equipment.
|||
||| I'm using a large ogee bit (1 3/8" radius) to creat a moulding
||| effect. So far I've done this exclusively on straight stock using
||| the router table. The upcoming project will need the same moulding
||| edge on an arched panel. This bit is large, almost like a panel
||| bit, plus I have very little experience routing freehand so I
||| don't think that's a viable option.
|||
||| I'm thinking that I could do this on the table if I position the
||| fence such that the curve of the piece indexes on the inside edges
||| of the split fence. i.e. "bridging the gap" with the bit inside
||| the gap as would be normal. I could easily adjust the depth of
||| cut for multiple passes and could still use a featherboardd to
||| provide downward pressure. I would still have to "freehand" the
||| work maintaining pressure towards the fence.
|||
||| Any thoughts on this technique or alternate ideas?
||
|| There's some important information you didn't provide:
||
| Good questions, and answers below:
|| [1] Is arch circular?
| No, it's irregular (parabolic).
|| [2] Width and height of arch?
| The piece to be worked will be about 24" along the curved edge. The
| curve is very gradual.
|| [3] Material to be routed?
| Spanish Cedar - one of the softest hardwoods.
|| [4] Thickness of stock to be routed?
| Thickness is 1". I was planning to cut the curve with a sabre saw
| and then route the edge. The deepest cut of the full profile
| amounts to about halfway through the stock (1/2").
|| [5] Are you routing inside, outside, or both curves?
| Outside only.
|| [6] What does "existing skills and equipment" mean?
| Without getting too long winded, I was referring to the thought
| process we all go through ahead of a project to plan how were going
| to create the individual components with the tools we have. Skill
| comes into the equation as well, for example cutting large sheet
| goods. Some people are skilled enough to cut large pieces on the
| table saw. I'm not, so I'd choose a circular saw with a guide. In
| the case of my current challenge, I'm very inexperienced with
| hand-held routing, so I hope to avoid attempting it with this large
| bit.
|| [7] Can you pre-cut the desired arch with a band saw and/or
|| straight router bit?
| I was planning to use a saber saw.
|| [8] Have you considered making a template to be used with a bit
|| incorporating a ball bearing guide?
| That's a possibility.

You're right - that /is/ a big bit to freehand safely (too big for me,
at any rate). If I'm understanding you correctly, I think you'd do
best to cut a template from tempered hardboard and use that in
conjunction with a 1/2" straight (with pilot bearing) bit to shape the
parabolic arch. This should permit a good smooth arch for appearance
and for use as a bearing surface for a second pass with an ogee bit
(again, with a pilot bearing).

In my shop I'd cut this arch on a CNC router - but I'd still do it
with the same two passes with a straight bit and an ogee bit. The only
difference would be that I wouldn't (couldn't) use bits with pilot
bearings. A 1/4" tempered hardboard template is fairly easy to cut and
is inexpensive. If you can, cut it just a "skosh" large and use a
sanding block to produce a smooth, true edge - it'll be less work than
truing the 1" workpiece.

Oh yes (I almost forgot to mention) - I've used carpet tape (kind of a
web with adhesive on both sides - available from lumber yard or
hardware store) to fasten templates to workpieces for this kind of
operation. Remove tape gently (solvent may help) so as not to tear
fibers from the face of your soft cedar.

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/solar.html