Routing a circle - Woodworking Talk - Woodworkers Forum
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post #1 of 16 Old 09-24-2020, 09:53 AM Thread Starter
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Routing a circle

Good morning, folks

I am making a shop stool, and need to cut a circle out of a 1-1/2" thick blank of Oak. I'm planning on using my router with a circle jig, but the longest bit I have is a 3/8" diameter upcut spiral with a 1-1/4" cutting length. Presuming I make multiple passes lowering the bit slowly, should I be able to make this cut, or do I need to find a bit with a longer cutting length?
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post #2 of 16 Old 09-24-2020, 10:04 AM
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I run into the same thing when I cut thick cutting boards on the CNC. The longest bit I have is about like yours so I cut to that depth, then remove the waste on the bandsaw. Then I use a flush trimming bit on my router table to clean the edge and finish getting it flush to what I cut on the CNC. Works great, actually.

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post #3 of 16 Old 09-24-2020, 10:42 AM Thread Starter
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Ah, great plan David, that's what I'll do then. Thanks.
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post #4 of 16 Old 09-26-2020, 06:14 AM
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Dave, Google how to cut circles with a table saw/bandsaw. It is a simple solution/alternative ... if you have either saw that is.

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post #5 of 16 Old 09-26-2020, 11:09 AM
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A bandsaw would be the safest and quickest way to cut oak that thick. many circle cutting jig plans are out there.

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post #6 of 16 Old 09-27-2020, 12:43 AM
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I use a 1/2" diameter, 2" long bit for making those sorts of cuts. BUT, I have had times when I needed to cut deeper than my bit. I have cut the full depth of the bit, then lowered the bit the remaining little bit to finish the cut. It's not a problem at all.
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post #7 of 16 Old 09-27-2020, 06:45 PM Thread Starter
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Quote:
Originally Posted by mmwood_1 View Post
I use a 1/2" diameter, 2" long bit for making those sorts of cuts. BUT, I have had times when I needed to cut deeper than my bit. I have cut the full depth of the bit, then lowered the bit the remaining little bit to finish the cut. It's not a problem at all.
Mark, just to confirm, that last little bit of routing is then done with a small part (in my case it would be ~1/4") of the shank of the bit riding along in the previously cut groove, correct? No drama of it "grabbing" the wood?
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post #8 of 16 Old 09-27-2020, 11:07 PM
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Its not a good idea to move the bit out from the chuck. The sideways forces on the bit, spinning at around 30,000 rpm, is colossal. I would not recommend doing that. Other people might have different values.

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post #9 of 16 Old 09-28-2020, 05:44 AM
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Make a template from 1/4'' plywood. Attach to the board and rough cut the circle with a saber saw or whatever tool you have. Rout halfway thru with a top bearing cutter. Turn over and rout with a bottom bearing cutter.
I haven't tried this myself but I think it would work well.
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post #10 of 16 Old 09-28-2020, 11:14 AM
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Quote:
Originally Posted by kwoodhands View Post
Make a template from 1/4'' plywood. Attach to the board and rough cut the circle with a saber saw or whatever tool you have. Rout halfway thru with a top bearing cutter. Turn over and rout with a bottom bearing cutter.
I haven't tried this myself but I think it would work well.
mike
I see router templates used and mentioned in a variety of contexts. The woodworking shows on PBS television do that a lot. It's like "swish and flick!" where they pull the perfectly shaped MDF or plywood template out of thin air, that solves the woodworking problem. What they fail to tell you is HOW they made that perfectly shaped template. It is frustrating, because that is the tricky secret that I want to learn more about.

As a general statement, it is relatively easy to follow a template around with a router if you have router bits with pilot bearings or guide bushings. It is making the accurate template that is the hard part for me.
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post #11 of 16 Old 09-28-2020, 07:58 PM
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Remove the Bakelite base, make another that is 1" or so longer than the radius of the circle. 1/4" plywood or almost anything you have in the scrap bin will work. The only things that have to be accurate are the mounting holes for the base and a nail in the new base for a pivot point.
Remember that the distance from the nail ( pivot) is to one edge of the cutter.
You did not mention the radius of the circle. I'll use 14" diameter or 7" radius as an example. Take a 12" x 7" piece of plywood and mark the base holes on one end. Scribe the perimeter of the base if you want . Could b left square. Find center of the new base and extend the centerline to the end of the plywood. From the center mark 1" each way for a 2" wide length . When done the jig will look like the Bakelite original base with a 2" tail. Install a straight cutter and measure from the edge of the cutter to the radius point in the example will be 7". You have marked the underside of the jig, bore a small hole thru and turn the router and jig right side up. I generally use a 6d finish nail for the pivot.
Mark the centerlines on the plywood . Set the router so the edge of the cutter is on the 7" mark. Rout the template.
You can make the template for either an inside or outside cut. I prefer an outside cut. If something goes wrong only the waste area will be affected.
Fasten template to the work , scribe a pencil line around the template. Remove excess leaving the line. Bandsaw ,saber saw, or what ever you have to remove most of the waste. Now you can rout with the top bearing cutter. Rout about halfway down. Remove the template and turn the work over. Rout the rest with a bottom bearing cutter.

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post #12 of 16 Old 09-29-2020, 02:51 AM
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Quote:
Originally Posted by Dave Mills View Post
Mark, just to confirm, that last little bit of routing is then done with a small part (in my case it would be ~1/4") of the shank of the bit riding along in the previously cut groove, correct? No drama of it "grabbing" the wood?

no. The cutters stick out farther than the shank. It's not a problem. And basically, you're only dropping the bit down another 1/4" or so. And if the person's comment about pulling the bit out of the chuck worries you, it's not even an issue for the long bits. There is plenty of shank between the chuck and the cutter, you just need to lower the bit past the upper edge of the cutter a little. You're not pulling it out of the chuck. Not that that is really a problem anyway.
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post #13 of 16 Old 09-29-2020, 02:56 AM
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Quote:
Originally Posted by sunnybob View Post
Its not a good idea to move the bit out from the chuck. The sideways forces on the bit, spinning at around 30,000 rpm, is colossal. I would not recommend doing that. Other people might have different values.

Sunnybob, are you familiar with 2" long straight bits? There is a good chunk of shank sticking out of the chuck. Cutting an extra 1/4" or 3/8" depth does not require you to pull the bit farther out of the chuck. Just lower the cutter a bit more into the wood.
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post #14 of 16 Old 09-29-2020, 03:51 AM
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There are mortising cutters that will cut up to 4-3/4" deep. These are speciality cutters for a PC lock mortising router gig.
Just mentioning too show that there are deep cutting straight cutters. I would never use them in any router except the lock mortising jig.
mike
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post #15 of 16 Old 09-30-2020, 02:52 PM Thread Starter
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I thought I should pop back in with the results.. Using difalkner's suggestion of routing most of the way through the wood (I got just over an inch into the wood) and then cutting the rest on the bandsaw, then tracing back around with a flat trim bit worked great. Finished up with a 3/4" roundover, and it's all done but a bid of sanding. Thanks all for the various ingenious ideas, which are always helpful!
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post #16 of 16 Old 10-07-2020, 03:03 PM
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A handy bit I bought a while ago was a 1/2" dia. 2" long straight bit with top and bottom bearings. Use it trimming doors and other things.
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