Circle cutting

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Forum topic by LotsofChips posted 12-20-2011 09:54 PM 1386 views 0 times favorited 12 replies Add to Favorites Watch
View LotsofChips's profile


6 posts in 2352 days

12-20-2011 09:54 PM

I need help cutting a circle with a shop made jig on the bandsaw. I made a jig and have the centering dowel slightly in front of the blade. I’m trying to cut a 24” dia circle on a 14” Grizzly with a 1/4 ” blade. The cut keeps spiraling inward. The blade was actually pulled from the alignment bearings. It moved inward 1/2” in a 1/4 circle. Any suggestions, set up? Thanks.

-- - Mike

12 replies so far

View interpim's profile


1170 posts in 3454 days

#1 posted 12-20-2011 10:06 PM

without seeing what it’s doing I really wouldn’t be able to offer many suggestions.

I would think you would want the pivot centered at the cutting edge of the bandsaw blade, and the guide just a hair above the wood. From there it’s only making sure your bearings are aligned properly. Also, try slowing down and see if it wanders less.

-- San Diego, CA

View DrDirt's profile


4424 posts in 3737 days

#2 posted 12-20-2011 10:43 PM

Try to have the center of rotation aligned with the gullets of your blade.
If the dowel is ahead of your blade it will spiral
Based on the geometry you describe – I would have expecte the bladt to be spiraling OUT with the dowel pin in front of the blade.

the effect is worse the thicker the material.

-- “The two most important days in your life are the day you are born and the day you find out why.” Mark Twain

View dannelson's profile


193 posts in 2366 days

#3 posted 12-20-2011 10:55 PM

one more plug for my microfence that is still for sale in the tools for sale/swap .no more jigs that need to be tweeked . a dead on accurate. I used to struggle with the same issues as you with cutting on the bandsaw before I bought the jig. $600.00 aint cheap but this is not a toy that collects dust.

-- nelson woodcrafters

View Elizabeth's profile


817 posts in 3139 days

#4 posted 12-20-2011 11:38 PM

I haven’t done a circle as large as that but when I first made my circle cutting jig I had the same problem. It turned out that my blade was not tensioned highly enough.

Edited to add – according to my notes on my project page, there was also a bit of play in the sliding part of the jig which was causing problems. I’d forgotten that.

View gfadvm's profile


14940 posts in 2685 days

#5 posted 12-21-2011 05:19 AM

I have had the same problem and now cut all my circles by scribing a line and following it rather than using a jig. I have been suprised how well this works. Once your blade starts to spiral, you have ruined that piece of wood and I got tired of that quickly!

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View ryansworkshop's profile


35 posts in 2362 days

#6 posted 12-21-2011 07:21 AM

This may not help, but do you have a router? I know we all want to master our tools to feel better about ourselves, but there is no way I’d spend $600 to cut a circle. Nor, would I want to make sure all the planets are in line just to cut a circle.

When I did use my band saw for cutting circles, I had CL (Center line) of pivot at the blade gullet, turned (fed) slowly and had the right tension. After, about a year of doing this, I looked over at my router stuff and like a ton of bricks, I saw the circle cutter base, I had bought on sale. Never looked at the band saw again for my circles.

When I turn big/thick stuff, I free hand to a compass line. Good enough for the lathe.

Always watch a lazy man, he will show you the easy way to get the job done.

-- A small shop has it's pro's and con's. Never big enough, but easy to clean.

View ScottN's profile


261 posts in 2675 days

#7 posted 12-21-2011 03:21 PM

I agree with Ryan. Forget the bandsaw and grab a router. Perfect cut every time.

-- New Auburn,WI

View kizerpea's profile


774 posts in 2363 days

#8 posted 12-21-2011 03:59 PM

Yes use a router an router table, my router table is 36”by 41” with a miter track..then make a slide for the miter track with a pin then u can ease it in until u get the dia like u want it. best tool i have made….my biggest circle is 33” to laminate the wheel for the band saw in my photo.


View rance's profile


4258 posts in 3156 days

#9 posted 12-21-2011 04:48 PM

Sounds like you have a blade drift problem. Fix that(and not by angling your fence) and your problem should be solved. Oh, and I’d center the dowel at the tooth part of the blade.

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

View superstretch's profile


1531 posts in 2688 days

#10 posted 12-25-2011 06:55 AM

I’d think you’d want the rotational axis in line with the teeth of the blade.. If you draw a top-down view of the geometry of it all, you can see the the blade angles in the way you describe it. You might also have drift, so you may have to adjust slightly forward or back. In either case, you definitely need to move the rotational axis back if you plan on using the BS

-- Dan, Rochester, NY

View LotsofChips's profile


6 posts in 2352 days

#11 posted 01-04-2012 12:54 PM

Lot’s of good things to try & I will, but, meanwhile, I purchased a jig for the router. Thanks all!

-- - Mike

View stefang's profile


15881 posts in 3329 days

#12 posted 01-04-2012 02:54 PM

All the above, but sometimes curiously enough, it can help if the the center line is slightly behind the teeth. This might be related to blade drift or whatever, but it might be worth a try.

If you center your blade accurately on the top wheel, you can pretty much eliminate blade drift altogether, providing your bottom wheel is in line with the top one.

This is because the tires on all but the largest machines are crowned, and it doesn’t take much off-centering to create big drift. If you take the width of your wheel and subtract the width of your blade and divide the difference by 2 you will have the amount of tire that should be exposed on either side of your blade when adjusted. It is smart to use calipers for this job as the eye is not as accurate and also the view angle is often not optimal.

A reasonably sharp blade also helps a lot. Good luck!

-- Mike, an American living in Norway.

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