Cutting perfect large circles

[Jack Ganssle]

Folks,

I want to build a round end table out of hard maple, and would like it to be really round - no bumps or other non-circular imperfections. I thought of cutting it close on a bandsaw and then trimming it round using a router and a round template. But... then I have to somehow make a perfectly round template first, which doesn't change the problem much.

Then there's the thought of putting a hole in the top's center (there will be one there anyway) and pinning it to the router table. Then, rotage the top and let the router bit chew away the perimeter. Question then, is, how to advance the assembly into the spinning router bit and then clamp it all down.

Any thoughts? And if a router is somehow the right approach, is a spiral upcut bit the right choice?

Jack

[Quinn McCarthy]

Jack

What I would do is build a circle jig for my router. They look like a big compass. You could use plywood for the arm. On one end you fasten your router and on the other you have a screw which gets put in the center of the table top on the bottom. After you rough it in on the band saw them you can clean it up with your router setup. If you are planning on making cirles quite often you could replace the plywood with adjustable rods that would be adjustable to any radius.

Hope that helps.

Quinn

[Karle Woodward]

You could use a circle cutting jig on the bandsaw (sounds like you were thinking freehand) and then smooth out the saw marks. Or the router with a simple circle jig and a straight bit would work too, but it'd be a lot of material to remove with a router. The best would be to use the bandsaw with the circle jig and then the router with jig to clean the edges. As for a hole in the center, it would need to be very deep and would only be seen from underneath.

[Brad Schmid]

A simple shopbuilt router trammel jigged on the underside of the tabletop, and a straight bit or spiral upcut would be my choice.
cheers

[Aaron Beaver]

Jack

What I would do is build a circle jig for my router. They look like a big compass. You could use plywood for the arm. On one end you fasten your router and on the other you have a screw which gets put in the center of the table top on the bottom. After you rough it in on the band saw them you can clean it up with your router setup. If you are planning on making cirles quite often you could replace the plywood with adjustable rods that would be adjustable to any radius.

Hope that helps.

Quinn

I was thinking like Quinn was, here is a link of one that you could buy, but building might be the way to go.
http://www.rockler.com/product.cfm?page=17282

[Jack Ganssle]

Good ideas! Thanks much, folks.

I should have thought of this. Too much time obsessing over the snow and a missed flight today.

Jack

[Steve Jenkins]

If you want to use a trammel with the router without bandsawing it first, set the radius a 1/16th or so too big and make multiple passes to cut all the way through then reset and make one full depth pass to clean up the edge.

[Al Killian]

Use the NYW bandsaw jig, then use the jig on the disk sander and it will be done quickly.

[Pete Bradley]

Circle jig on bandsaw would be my choice. Depending on the size of the circle and the size of your saw, a chunk of plywood with a nail in it, clamped to the band saw table may be all you need.

Pete

[Rick Christopherson]

For maple, you will defintely want a spiral bit to reduce tearout. Your trammel doesn't need to be anything fancy, and can be as large or small as you need it.

http://waterfront-woods.home.att.net/Projects/RoundTable/Trammel.jpg

[Mike Cutler]

Jack.

You got some great ideas already presented, but here is another just for fun

The MicroFence router jig hooked to a vacuum clamp in the center would do exactly what you want, with no hole in the center either. Problem is it would cost you more than a couple hundred bucks in jig and vacuum pump setup to do it.

Still though, food for future thought.;)

[Roy McQuay]

Hi Jack, you already got the right answers so I just wanted to say Howdy to a 'neighbor'.

[Doug Shepard]

Jack.

You got some great ideas already presented, but here is another just for fun

The MicroFence router jig hooked to a vacuum clamp in the center would do exactly what you want, with no hole in the center either. Problem is it would cost you more than a couple hundred bucks in jig and vacuum pump setup to do it.

Still though, food for future thought.;)

Got one and love it, but I didn't spring for the vacuum clamp. If you're looking for something to throw your tax return money at, it's hard to go wrong with anything that MF makes. The edge guide and plunge base for laminate trimmers are real sweet too.

[pat warner]

This one (http://patwarner.com/images/621_offset_2.jpg)(router) machined such that a 1/4" cutter in the collet will yield circles, precisely in 2" increments, starting at 4" ending at 12".
Plunging at ~ 1/8 - 3/16/pass will cut a pretty good circle.

[Carl Eyman]

The Martha Washington Candle Stand included in NYW current series of projects featured a new way of making a round table top. Norm mounted the table top outboard on his lathe and rigged up a router jig not only to make the top round, but also to hollow it out so it had a raised lip edge.

[Lee Schierer]

Lots of good ideas already suggested. If you use a circle cutting jig with your router and the top is made of solid wood, not plywood or particle board, then be careful as you do the cuts. On a solid wood top, you will encounter two areas of grain reversal which will tend to tear out unless you climb cut with the router in those areas. Caution: Climb cutting can be dangerous unless you have firm control of your router and only take a very light cut.