Routing an Arched Piece with a Large Bit


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?
Thanks, Tom
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tom snipped-for-privacy@comcast.net (in snipped-for-privacy@g43g2000cwa.googlegroups.com) 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:
[1] Is arch circular? [2] Width and height of arch? [3] Material to be routed? [4] Thickness of stock to be routed? [5] Are you routing inside, outside, or both curves? [6] What does "existing skills and equipment" mean? [7] Can you pre-cut the desired arch with a band saw and/or straight router bit? [8] Have you considered making a template to be used with a bit incorporating a ball bearing guide?
-- Morris Dovey DeSoto Solar DeSoto, Iowa USA http://www.iedu.com/DeSoto/solar.html
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Morris Dovey wrote:

Good questions, and answers below:

No, it's irregular (parabolic).

The piece to be worked will be about 24" along the curved edge. The curve is very gradual.

Spanish Cedar - one of the softest hardwoods.

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").

Outside only.

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.

I was planning to use a saber saw.

That's a possibility.
I think I misused the term "freehand". I meant "edge routing" using the bearing. With that big a bit, I afraid that it will be hard to control the router, especially since I'm very inexperienced. I'm getting pretty good at table routing so I'd hoped to find a way to do this on the table.
Tom

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tom snipped-for-privacy@comcast.net (in snipped-for-privacy@g49g2000cwa.googlegroups.com) said:
| Morris Dovey wrote: || tom snipped-for-privacy@comcast.net (in || snipped-for-privacy@g43g2000cwa.googlegroups.com) 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
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It's possible, but I think it'll get a little scary at the ends of your stock, without both fences in play. Maybe rough cut the stock extra long/wide to avoid the teetering, and give your fingers some extra room? Is there a bearing somewhere on this bit? Tom
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Do you have a fence for your router? If so, use it with a curved piece that matches the curve of the arch. Use it to follow the curve of the arch, in incremental cuts. Slow down the router, if you can. Good luck.
Steve

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With a 2-3/4" Bit? By hand? On the end of a long lever (edge guide)? I wouldn't try it.

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tom wrote:

Yep, that's the way to do it. With enough extra length, I won't have to get the end of the piece (or my fingers) any where near the bit and it will always be indexed on two points. The bit has a bearing, but the fence will control the distance from the cutters.
Great suggestion, thanks!
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I think everybody needs to know the length of the arch and the degree of the arch if possible.
There are several methods to make arched molding, and some are easier than others. The length of the piece is a "must have" before folks can be more helpful.
tom snipped-for-privacy@comcast.net wrote:

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It will actually be half an arch, because two mirror-image pieces will comprise the full arch (spaced apart slightly). Each half will be about 24" long.
Imagine the board laying flat against the wall. I'll describe the left-hand piece. The bottom will be straight (24") and right-hand edge will be straight (6") and the arched top will curve from the top right down to a point on the bottom left. There is no left edge because the arched top meets the bottom edge on the left. The arch is quite gradual.
Tom
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Like this: http://www.woodsmith.com/main/ws145toc.html
or
http://store.yahoo.com/backissuesstore/wsback67.html (no longer available)
I know the #67 copy uses a template to cut out the arch.
tom snipped-for-privacy@comcast.net wrote:

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On 25 Sep 2005 09:52:12 -0700, tom snipped-for-privacy@comcast.net wrote:

make a curved fence.
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tom snipped-for-privacy@comcast.net wrote:

Tom:
Here's how I approached a similar effort with routing small, curved raised panel pieces in 4/4 cherry for built-in bookcases:
1. Make MDF templates of everything you need to route. 2. Glue 2 handles to back of each template piece. 3. Cut cherry to slightly larger than template. 4. Screw template to back of cherry. 5. Route free-hand (with guide pin) in router table to flush trim cherry to template with flush trim bit. 6. Mount raised panel bit, crank router speed *waaaaay down* and route raised, irregular pieces.
Note:
- You'll have to make 3-4 (or more passes) with the raised panel bit. - Route across the grain first and then with the grain last. - For some curve pieces, it may make sense to route half the curve and then do a climb cut to get the second half. - Make the last pass *very* shallow (1/16" or 1/32") to remove any burn marks.
This effort was perhaps the scariest work I've done with power tools. Watching a 3" panel bit inches from your hands is a bit unnerving. Take your time and stay alert. You can do this safely, just think things through.
~Mark.
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