Blade flex?

[Peetie Wheatstraw]

Making an urn from 3/4" thick cherry I got from Rockler months ago. Cut 4 pieces 6" wide x 12" long. Set the old 10" Freud blade on the Craftsman (direct-drive) table saw to 45 degrees, and rip-mitre each 12" length, leaving a top tiny bit un-mitred so I can turn the work piece around and rip-mitre the other side.

The cuts were done very slowly and very carefully. No problem with the

45 degree angle, but the 45 degree 'surface' is a little wavy. Put another way, the 45 degree cut was very close to, but not quite s-t-r-a-i-g-h-t.

If I'm ever going to use this approach again, I gotta figure what went wrong. Obvious candidates for culprit are:

1.) My hands, i.e. if I let the piece float up above the TS surface. 2.) The table saw. 3.) The blade.

I very carefully 'greased' each piece with wax-paper and held them as steady as possible when cutting, so I sorta doubt that 1.) was the problem.

The old 10" Freud (maybe 60-t) blade wobbles a tad, but it generally looks pretty solid. If it flexed a little while under load, that would explain it.

How to test? Other possibilities??

Peetie

[John Grossbohlin]

End play in the arbor (shaft) is a possibility in that the blade could be moving "in and out."

Another possibility, that typically shows up with short boards, is that the fence is a bit wavy and the board was following the wave.

As an aside, I recall using an inexpensive Black and Decker circular saw with a jig to cut roof truss parts one time many years ago and the cuts were wavy.... finally figured out it was end play in the arbor that was the cause. Using the same jig with a Porter Cable circular saw and the cuts were flawless. Such a condition with a Craftsman direct drive saw would not surprise me at all.

John

[Michael Karas]

Arbor end play was also my immediate thought when I read the OP's message. I suspect that cutting with blade at a 45 degree angle also tends to aggravate the problem as the blade has more of an opportunity too waffle around as the cut is in process.

[Leon]

If you are using a thin kerf blade it would suspect that first.

[Peetie Wheatstraw]

There's more of an upward load on the blade when set at 45? Part of the reason I sorta suspected blade flex.

I checked the arbor: can't find any play whatsoever. Grab the shaft, push in, pull out, wiggle around, etc etc. Nothing!

Definitely worth checking.

Thx, Peetie

[Mike]

Wobbles a tad? I assume you mean you can see it wobbling as you are cutting. Does it do the same thing on a 90 degree cross cut? If it does, it seems to me that you have a bent blade, a bent arbor, arbor runout or the tilt mechanism has play in it. If it doesn't, I'd suspect play in the tilt mechanism that is held in check by being jammed against a stop.

I once had table saw that would crosscut fine if you were working on the right side of the blade, but make sort of wavy cuts if you worked on the left. Turned out the table had a small depression on the left side.

Mike

[Peetie Wheatstraw]

At 90 degrees, if I spin the blade with my finger, it "wobbles a tad". Put anothre way, the cut that it makes is a tad wider than the blade. It's been like that for a long time. But everything is as tight as can be, there is no play.

I see no evidence of the other conditions that you mention.

Peetie

[Peetie Wheatstraw]

Is any of this relevant? The issue was the blade, at 45 degrees, was -not- cutting in a perfectly straight line.

I just checked. I don't have a runout gauge, but when I cut a kerf in wood and place it back on the non-moving blade, there is near zero wiggle-space. I'm guessing my runout is not much more than yours.

In any event, the damned thing cuts a straight line when blade is set at 90 degrees.

Peetie

[Leon]

Again, is it a narrow kerf blade. Narrow kerf blades have a more difficult time making a truly flat cut when cutting at angles and bevels.

And near zero wiggle could mean 1/64", which is way too much.

[CW]

Again, is it a narrow kerf blade. Narrow kerf blades have a more difficult time making a truly flat cut when cutting at angles and bevels.

And near zero wiggle could mean 1/64", which is way too much. ================================================================ Depends. That much bearing run out is a problem. If it is just the blade running out, it won't hurt a thing.

[Mike]

==================================================================== CW, You stumped me. If the blade is moving (let's go with 1/64"), how is it OK if the blade is running out and not OK if the bearing is running out? I can't imagine how the resulting would be any different.

[CW]

==================================================================== CW, You stumped me. If the blade is moving (let's go with 1/64"), how is it OK if the blade is running out and not OK if the bearing is running out? I can't imagine how the resulting would be any different. ===================================================================== The term runout is actually incorrect in the case of axial movement of the bearing. Correctly, it would be called end shake. This is when the bearing, due to wear, improper assembly, et can move in the axial direction. There is nothing restraining that movement so it's position can change during the cut causing a wavy cut. In the case of blade axial runout (side to side wobble), it will not change during the cut. Say you have a bent blade causing axial runout. It does not matter at what point of rotation it is at, it will still be bent. As long as it is the same on every revolution, it will cut just fine but the kerf will be wider. Think wobble dado.

Each tooth

[Peetie Wheatstraw]

Wider, but still straight (other things remaining equal). Thanks, I needed that! :-)

Isn't it also possible that blade runout measured unpowered could be much greater than when powered due to the centrifugal force of the spinning blade?

Peetie

[CW]

Wider, but still straight (other things remaining equal). Thanks, I needed that! :-)

Isn't it also possible that blade runout measured unpowered could be much greater than when powered due to the centrifugal force of the spinning blade? ====================================================================

Yes. This is particularly evident in large blades like used in saw mills. When at rest, they look decidedly bent. As soon as they are running though, they straiten right out.

[Peetie Wheatstraw]

It purty much has to be the case with my old Freud blade. Spin it with my finger and the the runout is obvious, but when I put the kerf that it just cut over the (still) blade there is little/no runout perceptible.

Thx, Peetie

[Artemus]

There is another possibility in addition to the ones already posted. Your saw could be out of alignment. Assuming you have already got the blade parallel to the miter slots and fence, there is another adjustment that can cause problems when cutting with the blade at other than 90 degrees to the table top. The axis that the trunnion pivots about must be parallel to the table top too. You won't notice this on 90 degree cuts. If the rear trunnion mounts are lower than the front then the rear of the blade will be lower and, with the blade tilted toward the fence, form a funnel that the trapped piece is being run into. If the front mounts are lower than the board will tend to wander away from the fence during the cut and could cause the problem you are seeing.

Details and how to fix are here

'll probably need to register, but it's free and I've had no problems with spam coming from his site. Art

[Larry Blanchard]

I had a saw with that problem. Cheap imported contractors saw. I had to just about totally disassemble it to get to the front trunnion mounts which is where the shims were needed.

It's a shame that we can't buy a fully assembled saw so we could test it before it ever left the store.

[Artemus]

Make your own from wood. I did. If you don't have dial indicator -

more than adequate for the job, and many others. Art