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Problem cutting circles on bandsaw

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Forum topic by Tom posted 04-21-2017 02:27 PM 232 views 0 times favorited 5 replies Add to Favorites Watch
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Tom

151 posts in 666 days


04-21-2017 02:27 PM

I’ve got a Grizzly 14” saw and I’m having some issues cutting circles on my circle jig. If I use the 1/4” blade to cut a 2.5” diameter circle it works fine. If I put the 3/8” blade (Timberwolf i think) on it doesn’t cut right, the blade seems to be bending at the bottom of the cut piece so it’s at an angle. I’ve adjusted the tension and that doesn’t help.

Any suggestions?

It is possible that I left the blade with tension on it for an extended period but when I was changing the blades out it was pretty snug on the wheels. I do have it tracking correctly per Grizzly’s instructions so that shouldn’t be an issue. If I have a work piece on the table and cut curves they cut correctly.


5 replies so far

View mrg's profile

mrg

714 posts in 2605 days


#1 posted 04-21-2017 03:00 PM

Snug the blade a bit more. Don’t go by the indicator, go by plucking the blade.

Can you cut the 2.5 circle flat on the table? Or is it bigger with the 3/8 blade? Also try a larger circle and see what happens it may be a slightly to small of an arc for the 3/8 blade cutting with no support on the bottom with the jig.

Hope this helps.

-- mrg

View JBrow's profile

JBrow

1058 posts in 526 days


#2 posted 04-21-2017 03:21 PM

Tom,

I assume the feed rate is not excessive; the blade is sharp and properly tensioned; the upper guides are set close to the workpiece; the upper and lower guides are adjusted to support the blade; and the workpiece is held flat to the table.

Even if these assumptions are correct, according to the chart in the manual that accompanied my Grizzly bandsaw (a model different from your’s), a 3/8” wide blade can cut a circle whose diameter is as small as 2-1/2”. If Grizzly is correct, then cutting a circle with a 2-1/2” diameter is at the limit of the capability of the 3/8” blade. I personally like to stay away from limits.

However, Lenox publishes specifications that differ from the Grizzly manual. Lenox states that a 3/8” wide bandsaw blade will cut a circle no smaller than a 2-7/8” diameter circle. The Lenox chart is found on page 9 of their brochure. I could not get the link to post properly, but searching with the terms “lenox guide to bandsawing” should present the Lenox Guide to Bandsawing in the results.

A diameter smaller than the limit of the blade can sometimes be cut by making relief cuts from the edge of the workpiece into and up to the diameter mark defining the circle. These relief cuts would be needed in multiple places around the workpiece. As the circle is cut, pieces from the outside of the circle are released from the workpiece due to the relief cuts, giving the blade somewhere to go without bending or binding.

View Tom's profile

Tom

151 posts in 666 days


#3 posted 04-21-2017 03:34 PM

The diameter of the circle is around 5” which should be no problem for a 3/8” blade. I’m thinking that it may be the tension; I do have the guides set and keep them close to the work. I’ll have to try tensioning the blade more; maybe what I think is tight isn’t tight enough.

What’s odd…I used the 1/4” blade to cut a 4” thick work piece to cut circles and had no issues; just took my time feeding the material in.

View DrDirt's profile

DrDirt

4263 posts in 3348 days


#4 posted 04-21-2017 05:10 PM

You also want the gullet of the blade to be at that radius. So it can be that the 1/4 blade is cutting at the right spot on the circle – then the wider blade is now cutting 1/8 “out in front” of the circle jig, so it is being flexed as you rotate the board.

-- 'Political correctness is fascism pretending to be manners' ~George Carlin

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Tom

151 posts in 666 days


#5 posted 04-21-2017 05:25 PM

I’ll have to check that…it could be the issue.

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