Thread: Problems with circle cutting jig

Depends on a few things, besides the width of the blade, the width of the cut, the radius of the circle & the centre of the turning point on the jig with respect to the cutting point on the blade also come into play.

Thanks Cliff, so I can conclude that I'm doing something wrong then. The point of the jig lines up with the blade perfectly, the circle is not a small radius, in fact it was over approx 14 inches, it was about 1 inch thick and it was hardwood but I didn't think those factors would impact on the cut. I had intended to use this on much thicker material such as bowl blanks.

When cutting always in the same direction, e.g. clockwise, tooth set can become degraded more on one side than the other. You may be able to compensate for this by making the pivot point adjustable fore and aft of the teeth themselves. If side deflection is excessive, "barrelling" may occur, and the piece may not be removable.

Also, for bowl blanks, perfect circles aren't strictly required. Eight or sixteen straight cuts can accomplish similar objectives with less drama.

Cheers,
Joe

I suspect that 1/2 inch might be too wide for a 14 inch circle, maybe 1/4 to 3/8th would be better. You say the pivot pin aligns with the blade, but with 1/2 inch wide target, that covers a fair bit of real estate. Point centre should align with the points of the teeth.

Originally Posted by malb

I suspect that 1/2 inch might be too wide for a 14 inch circle,

I can cut a 4" circle with a 1/2" blade so that's not an issue.
If the pivot point is aligned then the problem is possibly a very blunt blade.
That and sap buildup when cutting green timber are the two things that I have found to cause bellying of the blade.

Thanks, boys, I'll try a sharper blade.

I whipped up a simple circle cutting jig in minutes. It made no sense to me to have to start dead on the edge of the board, or to have to cut a notch and start there. So rather than a stationary unit, I went the route of the jigs that allowed you to push the wood into the blade, then start your circle cut.

I pushed the first piece of wood into the blade, then started my circle cuts. The first two circles went wonderfully. Then I started having problems. Cutting the circles started pushing the blade off the tires.

I readjusted the tires, the bearings, I rubbed Budda's belly and walked backwards under a ladder. The latter two things worked, as long as I aligned the pivot pin so, from the right side of the saw, it lined up just in front of the blade. If I moved it back even an eight of an inch, I had a dull blade, or bad tire alignment, or misadjusted bearings, or . . . .

Now I understand the reason others have a stop on their guide. It positions it so when the wood is pushed into the blade, it will always stop at just the right place for alignment.

Originally Posted by Tiger

Thanks, boys, I'll try a sharper blade.

I reckon the placement of the jig is very important, as has been said. It should be adjustable, and be "aimed" at or a pfteenth in front of, the actual tip of the teeth where the wood meets the teeth. This assumes that the jig offers the wood up at exactly a right angle to the blade.