Rounding off an internal hole - Router Forums
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post #1 of 13 (permalink) Old 10-23-2017, 12:01 PM Thread Starter
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Question Rounding off an internal hole

I made a table saw sled yesterday. I used a drill to make a couple of holes and a jig saw to join them to make a couple of hand holes. Then I wanted to use my brand new router for the first time to 'round off' the holes.

Needless to say, after trying several ideas, I finished the larger-than-wanted holes with a rasp.

What would be the best technique for rounding off internal holes, please?
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post #2 of 13 (permalink) Old 10-23-2017, 12:17 PM
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Originally Posted by jazzzbo View Post
I made a table saw sled yesterday. I used a drill to make a couple of holes and a jig saw to join them to make a couple of hand holes. Then I wanted to use my brand new router for the first time to 'round off' the holes.

Needless to say, after trying several ideas, I finished the larger-than-wanted holes with a rasp.

What would be the best technique for rounding off internal holes, please?
I use a round-over bit with bearing pilot. The radius of the bit must be less than 1/2 the thickness of the material, or the bearing won't ride on the original surface when you round over the second side. Adjust the depth of the bit so that you get a round over without a ledge at the top surface. For internal cuts, you'll move the router in a clockwise direction to avoid the bit grabbing.

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post #3 of 13 (permalink) Old 10-23-2017, 12:18 PM
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A round over bit with a bearing should make it a quick and easy job using a hand-held router.
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post #4 of 13 (permalink) Old 10-23-2017, 12:23 PM
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round-over bit with bearing pilot.
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post #5 of 13 (permalink) Old 10-23-2017, 12:37 PM
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+1 what they said.

Think about it for a minute. If the material is 3/4 inch thick, a 3/8 inch round over bit will make a smooth edge. When run on both sides of the material, it will create a rounded edge because the cutter will meet from the other side. Or just do one side only, your choice.

A 1/4 inch roundover bit will also make a rounded edge that takes off the sharp edge wlhere you cut your opening.

Practice on some scrap. Adjust your cutting depth so the pilot bearing rides against your material, and the cut creates the rounded over edge you are looking for. You might have to adjust the depth up or down to get it right. Then all that is left is some light sanding. Should come out looking good.

BTW, round-over bits get used a lot in the wood shop.

Good luck.
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post #6 of 13 (permalink) Old 10-23-2017, 01:42 PM
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Exactly what Andy suggested.

Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
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post #7 of 13 (permalink) Old 10-24-2017, 06:42 AM
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+1 to the roundover bit suggestions. That's what I used on mine.

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post #8 of 13 (permalink) Old 10-24-2017, 07:58 AM
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As has been mentioned, a round-over bit with a bearing. The template is NOT required, it was still in place from routing the coin tray.
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post #9 of 13 (permalink) Old 10-24-2017, 10:37 AM
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I had a similar problem some time ago but I didn't have a rnd over bit with the profile or the depth of cut I required, the material I was working was too thin. I found 2 solutions that worked.

1. I drilled a similar hole in a 2nd piece of material then aligned both with a dowel and double sided tape.

2. I have a few non bearing ovolo bits, one with the profile I required, I plunged the bit into the hole to align it then used double sided tape on wood strips to block the router base in place

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post #10 of 13 (permalink) Old 10-24-2017, 03:03 PM
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I just did this yesterday. Had a 1X3 inch slot. I wanted to round the edge over so I used a round over with a bearing and ran scrap wood until I got it like I wanted then ran my piece over it.
Same as everyone else said.
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