Blade Runout

[dcamron71]

Not sure if this is the right term. I was adjusting my tablesaw last night (blade parallel to miter slot) and noticed that the blade varies by .004. I have 0 runout on the arbor flange. Is .004 acceptable? The saw runs smooth and cuts great by my standards but I was wondering if .004 is typical, high or OK?? It makes me wonder if I should align the back of my fence further over at the back. Also, I use blade stabalizers but haven't checked those. I'll do that tonight.

[Charlie Self]

Typical of a good set up, IMO. If you want to kick the back of the fence out, do so, but it's not really essential if you're parallel now, and not having kickback problems.

[Joe]

.004 is the thickness of a sheet of 20# "copy" paper.

For comparison, a Forrest blade is straightened to between .001 and .002.

at a .004, I'd lay a straight edge across the blade to check it. It seems a bit high to me.

But the real test is how well it cuts. You said you're happy with it. Does it leave saw marks on the side of the boards after ripping? If you can live with the cut that you're getting and you feel you're safe from kickback, don't sweat it too much.

[bridgerfafc]

not sure if you're using the right terms either. are you thinking that toeing the fence out at the back will correct for what you're calling runout because you're calling the parallelism between the fence and the blade runout? if so that's not runout.

runout is wobble. it's the amount of variation from side to side in the path of the blade as it rotates and has nothing to do with the fence. table saw runout can be because of an out of true arbor flange, a warped shaft or a warped blade.

the fact that you measured .000 at the flange leads me to believe that you understand what runout is and that your problem is in fact a warped blade. do you have another blade you can test with?

[Leon]

You want the fence parallel. Tipping the back out from the blade simply masks a problem and creates worse tooth marks on the waste side of the cut.

Forrest can flatten that blade for you if you are not happy with the results.

I want both the keeper and waste side of the wood being cut to have no tooth marks as I very often use the waste piece also.

[Frank Boettcher]

Blade runnout and fence/slot to blade alignment have nothing to do with each other so you will probably have to clarify what you mean.

If your arbor flange mounting face is truly "0" runnout then you are a statistically lucky fellow. A spec of .0005" max. for a high quality saw would be normal.

If your blade runnout measured with the blade mounted on the arbor at the maximum measurable point on the blade is .004", still pretty good, although with a "perfect" arbor reading you're losing quite a bit with that blade.

If you mean something else altogether you may want to offer additional information to clarify.

Frank

[Jim Weisgram]

You might check just the stabilizer mounted in place of the blade, see if it has measurable runout.

Also bear in mind a 10" blade will magnify any runout measured at the arbor due to the much larger diameter. It is possible the blade is flat but the arbor has < .001" runout. I assume you used a dial indicator to measure this.

You can see what happens if you rotate the blade 90 or 180 degrees relative to the arbor and remeasure; you might luck out and reduce the runout by offsetting runout in the blade vs. the arbor.

[dcamron71]

Thanks for all the help on this. The flange on my arbor is immeasurable with a .001 dial indicator. So is the blade to miter slot. I've never noticed the blade being bent before so I was wondering if it would be a problem. Especially with kickbacks. I align my fence exactly to the blade but considered moving the back away from the blade by a bit to reduce the chance of kickback. That's why I was wondering if .004 was considered excessive. I checked the stabilizers last night and they're also immeasurable at the edge. I still don't have any vibration or cutting issues so I guess I won't worry about it unless I see a problem.

[DonkeyHody]

I don't think .004 runout on a 10" blade is anything to worry about. If memory serves, my Freud Glue Line Rip blade has .003 runout, and it produces sanded-smooth edges. None of the major manufacturers go to the trouble to make truly flat saw blades. If they did, we wouldn't be able to afford them. Runout shows up as a slightly wider kerf, and more pronounced tooth marks, but it shouldn't contribute to kickback at all. It's more important to mark a tooth on the blade and make all your measurments from that same tooth. Then runout becomes simply a cut quality issue instead of an alignment issue.

Ed Bennett's website is very good at separating the wheat from the chaff, even if you don't need his very fine products. Go to www.ts-aligner.= com and wander around a bit. Be sure to find the page on alignment myths.

DonkeyHody "Every man is my superior in that I can learn from him." - Thomas Carlyle

[Swingman]

How did you measure this? The acceptable way with a dial indicator:

With the instrument, find and mark the high spot on the blade; loosen the nut and turn the blade 1/2 turn on the arbor; re-tighten the nut check for the high spot again; if the high spot coincides with the marked spot, then the it's due to blade warp, if not, then it's arbor/flange runout.

If you didn't do the above, you may be fooling yourself ...

If your saw/fence system allows you to use the fence on both sides of the saw blade, I would not do it ... otherwise, it appears to be a matter of preference.

Strictly my tuppence ... YMMV

[Swingman]

"DonkeyHody" wrote

I don't think .004 runout on a 10" blade is anything to worry about. If memory serves, my Freud Glue Line Rip blade has .003 runout, and it produces sanded-smooth edges. None of the major manufacturers go to the trouble to make truly flat saw blades.

I agree with you ... if the blade cuts to your satisfaction, I wouldn't worry about .004.

IIRC, Forrest supposedly has a _factory_ tolerance of +/- .001 for blade flatness, but I'm willing to bet that very few stay that way after the dings and bumps of everyday use.

[DonkeyHody]

It's more important to mark a tooth on the blade and make all

Correction: I should have said mark a SPOT on the body of the blade near a tooth and make all measurements from that SPOT. Teeth, being somewhat sharp and angular, don't lend themselves to repeatable measurements.

DonkeyHody "We should be careful to get out of an experience only the wisdom that is in it - and stop there; lest we be like the cat that sits down on a hot stove-lid. She will never sit down on a hot stove-lid again---and that is well; but also she will never sit down on a cold one anymore." - Mark Twain

[Frank Boettcher]

Certainly without a definition of "truly flat" I would challenge the comment that manufacturers do not go to the trouble. Having to sit through many, many evaluation sessions of pilot blades in the 10" to

20" size range in a transition from Leitz to Oldham, in which axial and radial runout, hole true location, size and ovality or lobing, body polish and flatness were reviewed and discussed ad nauseum, I know that some and probably many blade manufacturers are fairly obsessed with the subject of quality.

Frank

[DonkeyHody]

Frank, By "truly flat", I meant "no measurable warp". I didn't mean to imply that manufacturers aren't concerned about quality. I think the better blades from several manufacturers have more precision built into them than most of us can use. I only mean that even the best blades will have measurable runout and that we shouldn't assume the blade is faulty because we can measure the runout with a dial indicator. I think the law of diminishing returns keeps even the best manufacturers from chasing down that last bit of measurable runout. If they did, their production costs would rise substantially without a coresponding rise in discernible quality.

DonkeyHody "Even an old blind hog finds an acorn every now and then."

[Frank Boettcher]

You realize that there is no such thing, statistically. All things in their final state in nature, all processes designed by man have some statistical curve of variation associated with them. The ability to measure exceeds the ability of any repetitive process, no matter how good, to "eliminate" that variation.

But I understand and concur with your point as stated below.

Additionally, my experience would suggest that there is a vast difference between manufacturers with regard to the "trouble" they go to to assure flatness or any other feature on a blade. Probably better than your general statement that none go to the trouble. You don't want to leave any reader with the impression that a blade is a blade. Many good ones, often referenced here, some not so good, not often discussed because no one uses them, at least for precision work. Further confusing the matter is some of the good manufacturers have different quality lines, and some do not.

True.

Frank

[whit3rd]

I have a single saw blade in my collection that has lower runout than that, and I've marked it "test blade" so I don't accidentally use it to cut something. It gets a few minutes service time whenever the table saw gets realigned.

Your runout is acceptable, IMHO, but might change if you loosen your blade and rotate the flanges and stabilizer disks, just in case there's a speck of sawdust in the assembly, then retighten.