circle cutting jig

[Carl]

Hello to all.

Doe's anyone know how to make a jig for the bandsaw for cutting circles, I have tried cutting one free hand which ends up with a flat spot or the diameter differs. I want the circle for a home made sander.

Carl :?:

 

[wizer]

There is an excellent Router jig by SteveM in this months British Woodworking.

 

[Tom K]

I know a man who does :norm:
It essentially involves making an extended support table with an adjustable pin. The radius of the circle is the distance twixt blade and pin and then you just keep feeding until you have a complete circle.
HTH

Regards Tom

 

[jhwbigley]

are you making a disc sander? if so i can tell you that just need to cut it best you can free hand than once it is fixed to the motor, turn it on and sand it round with a block of wood and sandpaper.

jhb

 

[Steve Maskery]

Tom, thanks for the plug! Have your mags arrived yet?

Carl
Cutting circles on the BS sounds simple - in practice it is fraught with problems. Just as a blade can drift when trying to rip, the blade can do the same when cutting circles. The result is a spiral cut and you end up with a disk that has a discontinuity where you started.

The solution is to make the pivot point adjustable to and fro. If the spiral is getting bigger as you cut, move the pivot point towards you. If the spiral is getting smaller, move the point away from you.

I have an old article, with not-very-good illustrations (pre-Sketchup). If you send me your email address I'll hunt it out for you.

Cheers
Steve

 

[Derek Willis.]

Cutting circles on the bandsaw is never very successful as others have said, use a Router with a home made circle cutting jig, just a base with a central hole for a small guide bush, and extended arm to pin through and there you go!!!
Derek.

 

[maltrout512]

I have seen a similar jig for doing circles on the table saw. I've not bothered trying, if and when I need a circle I use the lathe, this can handle upto 32 ish inches.

 

[DaveL]

when I need a circle I use the lathe, this can handle upto 32 ish inches.

This sounds like a gloat to me, makes your lathe sound like a monster, I can do ~ 3 1/2" on my lathe. :roll:

 

[Derek Willis.]

I can do none on my non-existent lathe, so Router it is.
Derek.

 

[mailee]

I always use a jig I made for the router to cut circles. Simple affair with a baseplate to mount the router on and a long arm with a slot running it's length into which I place a screw. Loosening the screw and adjusting it's length gives me the radius I desire. HTH. :wink:

 

[Jonzjob]

I had a commision to make 8 5 foot diameter MDF table tops for a local hotel. I got the supplier to cut the 5 X 10 sheets of MDF in 1/2 for me a struggled them home. I made a circle cutting jig from some scrap board with 2 stair carpet rods set in it. The board was pinned in the centre of the MDF and my router was adjusted to the radius. I cut a slot about 1/2 inch deep and cut round in the slot with my jig saw. It was a simple job then to finish the round with a top bearing guided router cutter. It was a lot easire than trying to cut full depth with the jig. hey were finished off with a 1/4 round bottom bearing cuter for a nice job.

My Startrite 301S band saw has a circle cutter on it and the only modification that I have done is to scribe a line at 90 deg and in line with the front of the blade so that when I have set the rad correct I can line it up perfectly with the leading edge of the blade and cut up to about 10 inch dia circles every time.

 

[Derek Willis.]

Jonzjob,
I usually use a jig for one of my routers for the cutting of circles, when I have cut the circle, I always save a pattern in M.D.F. so that next time I can just use the blank and a pattern following bit.
Here are two of my jigs made for different routers, you can, of course, make the jig out of thicker material and make a hole in the centre to take a guide bush , then just drop the router and guide bush in and turn.

 

[Jonzjob]

The top one looks very similar to mine Derek, but the rods on mine are, as I said, old stair rods. I don't know where they came from but I have dozens of them?

Fortunately a 5 foot dia pattern was both out of the question and un-needed thank goodness!

About the only patterns that I have are for the various toys that I have made. I hadn't thought about it before, but I have a photobucket album that I have just done. It shows some of the bits that I have made over the years.

I think that the most testing commision was to turn 5 dozen eggs! Ranging from Kestrels size up to Golden Eagle. They were for a falconary centre that used to be near Gloucester and they wanted them to replace newly laid eggs so that they could be hatched more safely in an incubator. Was I ever glad to see the back of that job. No copy turning either. Now I realise just why a femail Golden eagle has such a wicked look in her eyes. I would if I had layed something that size!

Sorry, I am going off topic here. Done now.

 

[jimi43]

WOW Derek...that is SO spooky! I just took a gander at your right hand picture and it reminded me of one I did for making semicircles for my Vox guitar amp speaker grilles! That is so weird!

I use pop rivet pins to pivot on...they fit beautifully and tight. Mind you the guidehole jig is far more sophisticated...wish I had thought of that at the time...never mind!

Cheers

Jimi

 

[Derek Willis.]

Try this one, has to be the simplest circle jig known, a strip of mdf. hole for a guide bish and a pin,
Derek.

 

[Giff]

Derek I have just seen your solution for cutting circles
with a router and must say it''s simplistically brilliant ! Giff

 

[Derek Willis.]

Giff,
Hope you use it, and welcome to the forum
Derek.

 

[jclaude]

I suppose Carl is a little disappointed, he asked for a BS jig and got reply on router jig.
I have to say I use both, the BS for large circles, the router for smaller ones.
I have a pdf file with a BS jig, not the one I use but this one seems promising, and is on my to-do list. But I don't know how I can join it.
Cark, if you read, drop me a message I will push it to you.

Jean Claude

 

[loz]

Have a look here

http://www.sawg.org.nz/

projects page - bandsaw jig.pdf

Lookgs exactly what you are after.

Loz

 

[Derek Willis.]

For a bandsaw circle cutting jig, simply have a false table of mdf, locate it on the table, slide it through the blade until you have it fitting the table, and then cramp it.
Take the timber you want to turn into a circle, from the edge , at the radius point, with the edge touching the blade, pin to the false table,then simply turn the timber until you have completed a complete circle. Of course you will need a narrow blade to do this as with any other style of jig.
Derek.