Saw Blade Run Out

[Ken Krawford]

I just got my Forrest Woodworker I & II blades back from being sharpened. I have the WWII on my radial arm saw and the WWI on my Unisaw. I noticed that the WWII had a bit of wobble as the blades was spinning down. I pulled out my dial indicator and measured 11/1000 run out. The WWI on the table saw only had 5/1000.
Any idea how much run out is acceptable?
Thanks.

[johnny means]

Does it affect your cut? Numbers don't mean anything.

[Paul Murphy]

Your .011" runout is too much in my opinion for a premium blade on a good saw. Opinions vary, but I see .006 as the upper limit of total runout.
Next question is where is the runout? Blade, arbor, flange, foreign material @ flange? Do some checking.
Forrest advertises something like .002" max runout, and an arbor should have .001" max runout @ flange face. You can see a perfect blade mounted on .001 runout flange would have proportionally more runout at the tip of the blade, around .oo4" -.005".
Often you can spin the blade to cancel some total runout, remount at 90 degree increments and check.

I bought a new arbor for my saw which was .0005" runout, and with a quality blade I can often zero total runout. When all this really matters is cutting sheets of expensive veneer plywood, or melamine which will chipout if anything isn't right.

Hope the cure is something simple, like cleaning your arbor flange of sawdust :).

[Phil Thien]

Swap the two blades around. Does the runout stay with the blade, or with the saw?

If the runout stays with the blade, ask Forrest to take a look at the blade that wobbles over 1/100th of an inch.

If it stays with the saw, you may need to replace bearings on the radial arm saw.

[ian maybury]

Could be that some dirt or whatever on the arbour might throw it a bit too...

[Mel Fulks]

A friend who ran a sharpening service for decades used to have a flat plate for testing for warp. He would bang them flat before sharpening.Kept a little timer that was started as he picked up each saw,if he straightened it before the the time ran out there was no additional charge. Don't know if that is a widely used practice.

[Ronald Blue]

That is definitely excessive. If you can see it especially but the cut quality will show it as well. It definitely needs be less the .005 and the closer to .000 the better. I think that you will see "swirl" lines in rip cuts especially and probably some raggedness in crosscuts. As has been mentioned check the flange for run out but also make a mark on the blade with a marker and check it, loosen and rotate 180 degrees and recheck. I have a spring loaded arbor nut that allows putting the blade on and checking it for run out. It is part of the deluxe A-Line It kit. Keep us posted on what you find.

[Ellery Becnel]

Ken
Start with the arbor run out. Then check the face of the arbor where the flange runs. Make sure the flange faces are flat. Use a flat
honing stone to check for high spots. If all is acceptable, it is probabbly in the blade. It may be twisted or warped. Either way you
will know for shure where the run out is. Try different blades and compare readings. Once you have identified the problem you can
correct it. Let us know what you find. It will help us if we should have similar problems.
Thanks Ellery

[scott spencer]

If that's total runout, you need to isolate whether is the saw or the blade before you speak to the blade manufacturer.

[johnny means]

I still say, "hows the cut?" That much runout is well within a blades normal range of movement during actual use. Just look at your ZCIs, very few of them are going to be within.0001 of your blade. This is because a blade naturally flexes a little in use. The only guaranteed effect that a miniscule wobble willhave is a slightly wider kerf. My point is that the proof is in the pudding. Why not cut some would and then start solving problems, if there are any.

[Richard Wagner]

When I tune my table saw, I target for not more than .005" runout. With those quality blades and a Unisaw, achieving that number should be a cinch.

[Chris Fournier]

When I tune my table saw, I target for not more than .005" runout. With those quality blades and a Unisaw, achieving that number should be a cinch.

I am curious as to what your tuning process entails that would allow you to effect the runout of your TS arbor? Run out is pretty much a function of production tolerances and I am unclear as to what a woodworker can do to improve these tolerances.

[Paul Murphy]

I am curious as to what your tuning process entails that would allow you to effect the runout of your TS arbor? Run out is pretty much a function of production tolerances and I am unclear as to what a woodworker can do to improve these tolerances.

If your arbor has minor runout, and your blade has minor runout, then depending on rotational mounting you either cancel some runout or add it all together.
If you don't like your first result, loosen the blade and rotate 90 degrees and remeasure. Repeat until minimum runout is measured.

[Chris Fournier]

Table saw baldes, good ones at least, are tensioned by the manufacturer or sharpening shop to run true at specific RPMs. A properly tensioned saw plate may well have runout as you turn it by hand for the indicator. Trying to accumulate minimal runout by turning your blade on the arbor seems reasonable but may not have any bearing during operating RPMs.

[Phil Thien]

Table saw baldes, good ones at least, are tensioned by the manufacturer or sharpening shop to run true at specific RPMs. A properly tensioned saw plate may well have runout as you turn it by hand for the indicator. Trying to accumulate minimal runout by turning your blade on the arbor seems reasonable but may not have any bearing during operating RPMs.

How does a manufacturer tension a blade for a specific speed?

I had figured they knew how much a blade would flatten at speed, and just made sure the blade was flat "enough" at rest that it would be within spec at speed.

[ian maybury]

Blade flatness is a bit of an intriguing question. I'm for example always surprised at the amount of run out in the plate just under the teeth on my Felder blades when setting toe out - it really underlines why it's important to mark a spot and keep returning to it.

The other issue I tend to run into is that no matter how carefully I line a tooth up with a mark the blade never quite cuts to it. Which isn't too surprising if there's possibly up to .010in wobble in the mix.

I've for example checked the runout on my arbour and it's well within limits.

It all begs the question of what the best total blade handling regime is for precision work - from what to check for when buying blades, through checks on fitting fitting and technique for using it...

ian

[Mike Heidrick]

Check the rake angle too - I believe you want the WWI on the RAS and the WWII on the tablesaw.

[Chris Fournier]

How does a manufacturer tension a blade for a specific speed?

I had figured they knew how much a blade would flatten at speed, and just made sure the blade was flat "enough" at rest that it would be within spec at speed.

A blade does anything but flatten at speed! The stresses of cut entry and exit also cause the saw plate to move. On top of this heat will affect the flatness of the plate too. The following link gives you a good over view of the TS plate tensioning process. I have been fortunate enough to observe the operation; the folks that do this work have some serious time in the industry!


http://www.carbideprocessors.com/pages/saw-blades/steel-saw-plate.html

My TS can run at 3500 RPM and 5000 RPM. I had three blades from a manufacturer that were atrocious out of the box. I had the supplier retension them, no luck. I took the blades to my new tooling supplier and they re-re-tensioned the blades for 3500 RPM (5000 RPM is furiously loud and I don't require high feedrates). The cut quality and runout were noticably better to the naked eye. The blade plates are covered with hammer blows.

[ian maybury]

Interesting piece Chris. No simple answer then - while thre are things you can do afterwards to optimise the set up, if you get the wrong blade set up it's going to be problematical.

Discs are inherently unstable anyway - just warm one up and it twists because it incorporates multiple diameters/circumferential lengths.

Does that I wonder mean that as well as buying the right brand and specification of blade the option exists to buy blades tuned for specific RPMs too? I don't think I've seen it, but maybe just wasn't looking in the right place?

Maybe it's the case, but not explicitly said so as not to deter buyers.

A quick look around just now suggests that for example Felder and Hammer saws tend to run around 4,800RPM, while most US pattern table saws run more like 3,600 RPM. (which explains the quite high noise level from my Hammer K3)

Wonder if this is enough of a difference to require selecting the right saw blade? It'd suggest for example that there may be good reason to go for OEM Hammer or Felder Silent Power blades. Wonder if there are other blades made specifically for higher rpm Euro pattern saws, or if there are makers producing blades to suit both speeds?

ian

[Jim Brown 2]

Some years ago I had an old table saw with about the same run out as you have. I took the trunnion off the saw and brought it into a machine shop for a commercial woodworking machine distributer and they trued up the arbor flange and also replaced the bearings for a very reasonable price. Not sure what they brought it into as it was about 15 years ago and I no longer have the saw.

[Chris Fournier]

Interesting piece Chris. No simple answer then - while thre are things you can do afterwards to optimise the set up, if you get the wrong blade set up it's going to be problematical.

Discs are inherently unstable anyway - just warm one up and it twists because it incorporates multiple diameters/circumferential lengths.

Does that I wonder mean that as well as buying the right brand and specification of blade the option exists to buy blades tuned for specific RPMs too? I don't think I've seen it, but maybe just wasn't looking in the right place?

Maybe it's the case, but not explicitly said so as not to deter buyers.

A quick look around just now suggests that for example Felder and Hammer saws tend to run around 4,800RPM, while most US pattern table saws run more like 3,600 RPM. (which explains the quite high noise level from my Hammer K3)

Wonder if this is enough of a difference to require selecting the right saw blade? It'd suggest for example that there may be good reason to go for OEM Hammer or Felder Silent Power blades. Wonder if there are other blades made specifically for higher rpm Euro pattern saws, or if there are makers producing blades to suit both speeds?

ian

My current supplier gives a speed range for each blade Ian. I have not had any problems with their blades on my saw. I guess my point is that checking for run out as many have mentioned here is not really that helpful once things are up to speed. Now checking an arbor is indeed helpful but a fix for an arbor that has significant runout is well beyond any TS tuning that can be done in the woodshop.

[Myk Rian]

very few of them are going to be within.0001 of your blade.
Umm, that's 1 ten thousandths. I think you mean .001, which is 1 thousandth.

[Paul Murphy]

Runout.

Well none of us can directly measure runout at speed in our WW shops. Indirectly we have an indicator in cut quality.

If you start with a lot of runout, you can certainly expect it to get worse once you bring the blade up to speed.

In my experience I get the best cut quality with any blade when my total runout is near zero. As always a good ZCI helps considerably with cut quality in difficult materials.

If I am installing a known flat blade on my known saw with low runout I don't check runout again unless there is a problem. My blades with higher runout are reserved for cutting MDF or rough sizing material at the beginning of a project.

[Tom Walz]

Good big box blades usually have a runout onthe blade of 0.003" to 0.005".

Top end 10" blades have a runout of 0.0005" or less.

You flatten a blade by hammering.

You can tension a blade with a roller. Imagine a roller with one or more head that roll a groove maybe 1/4" wide. These change the structure of the steel a bit by compressing it.

Saw blades, even 10", have critical speeds to them. At the first critical speed the saw blade will flutter in 2 directions (or one direction and the reverse.) If you keep speeding up the rotational speed then the flutter will disappear until you hit the second critical speed where the saw blade will flutter in four direction (sometimes referred to as potato chipping- because it looks sort of like a potato chip when captured by high speed cameras.)

Lowell Freeborn explains it also:
http://www.carbideprocessors.com/pages/carbide-saw-manual/csm-hammering.html

You can have a digtal copy of the Freeborn Carbide Saw Manual free from us. You can buy a hard copy on http://www.carbideprocessors.com/pages/media/books.html

I made a deal with Mr. Freeborn to distribute the digital edition free and only charge for production rights for a hard copy.

[Tom Walz]

Saw blade runout is now being measured in tenths of thousandths of an inch. This is a free running blade. Not much point in a blade this good unless you are feeding it properly.

[Richard Wagner]

You are absolutely correct. I do nothing to overcome runout. All that I do is attempt to eliminate unnecessary contributors to runout; things like unwanted debris on the arbor shaft or blade.

My comments were really about blade/table alignment. I totally missed the point.

[Andrew Pitonyak]

You can have a digtal copy of the Freeborn Carbide Saw Manual free from us. You can buy a hard copy on http://www.carbideprocessors.com/pages/media/books.html

I made a deal with Mr. Freeborn to distribute the digital edition free and only charge for production rights for a hard copy.

Is there a download link? I don't see one...Or does that come with the book if you purchase a printed copy?

Side note to Tom: Give a thank you to Emily for me. I made a mistake with my order and Emily had to go to a bit of effort to fix it for me. Outstanding service (as always).

[Tom Walz]

Dear Mr. Pitonyak:

That is an excellent idea. I will ask Renee to do it for you.

I am incredibly fortunate to have two very nice ladies that truly enjoy customer contact. They really like helping people. While everyone is treated a being the special person they are, they do recognize your name and we all genuinely appreciate you repeat business.

Sincerely,

Tom Walz
President
Carbide Processors