Cutting Large Circles

[Sshado]

How do you cut large circles?  I need to cut a 10" circle out of 3/4" Oak Plywood and I am wondering if there is anything better than a Jigsaw for this.

Thanks,

Sshado

[Veto]

really big drill bit?

[Pixelhugger]

I believe you can use a router with a circle jig. Never done it/seen it myself.

[RandyT]

Some routers have a circle cutting jig, or at least a way to use one.

This usually consists of a metal rod with a right angle bend on one end, and the means of clamping the other end to the base of your router.

You then drill a hole that is the same size as the rod diameter at the center of where you want your circle.  Then attach the rod to the router base so that the inside edge of the bit is at the radius of the dimension you want, if you are after the disc.  

*edit* If you are making a hole, measure to the outside edge of the bit.

Then just spin it around and cut it out.

A word of caution:  Make sure you have a waster board underneath and your rod goes into that as well.  Otherwise, as you finish your cut, there will be nothing to hold the rod and your cut will get ugly.

RandyT

[Wienerdog]

You can also build a router jig out of pegboard or hardboard.  

Cut a scrap piece of pegboard (or any wood for that matter, pegboard just has some holes already.  If you use hardboard, you can drill your own hole) into a 5" x 3' piece.  In your case, you would only need a piece about 12" long, since the center of your circle will be 5" from the router bit.

Remove the base plate of your router, and screw the wood to the router using countersunk screws.  You will have to cut an opening for your router bit to fit through.  Now just measure the desired distance from the router bit and drill a hole at the centerpoint of your circle.  If your really wanted a 10" wooden disc, then measure 5" from the inside of the router bit, if you wanted a 10" hole, then measure from the outside of the router bit .

Opps, I should mention that this process is easier with a plunge router.  I've done it with a fixed base router, but it is tricky to start the cut...

[thedemo]

you could invest in a Rotozip kit for about $90. The kit comes with the Rotozip itself, a grinding attachment for metal and wood and a handy attachment for making circles up too I think 20 inches across.

[shmokes]

Here's what I do.  Get a 5" length of rope and nail one end of it into the center of the the soon to be circle.  Nail the other end into the side of your circular saw and let her rip.



Just kidding.

[OSCAR]

I have both of these and they work great.

Large circle jig

Small circle jig

[Wienerdog]

Here's what I do.  Get a 5" length of rope and nail one end of it into the center of the the soon to be circle.  Nail the other end into the side of your circular saw and let her rip.

Just kidding.

You have to start that procedure off with a six pack of beer to steady your hand.

I am also just kidding, but all non-powertool related procedure should start off with a six pack.  

The first link from Oscar is what I was describing.  You can build a quick jig, but it is obviously better to purchase a good quality one like that.  Basically the polyethylene material will be much better than fiber board at 1/4", but that doesn't mean you can't whip one out with fiber board if you need a quick jig.  Just make sure it is safe.

[hyiu]

that is a very nice tool !!! oscar...

I think the small one is worth the $$.....
soon.... I'll need to cut a 3" hole for the trackball....

thanks....

its nice to learn something new here everyday....