What is "runout"

[Chris Yarish]

I have been reading some table saw tuning tips and "runout" is referred to with both the blade and the arbor.
I have no idea what this refers to.

[David DeCristoforo]

Runout refers to the arbor (or blade) not turning in a true concentric circle. The causes are numerous but usually have to do with misalignment of the bearings causing the arbor to "wobble" slightly. Almost all machines have some degree of runout but it is typically much greater on cheaper equipment.

YM

[Greg Peterson]

Lateral movement on the horizontal plane in relation to a vertical axis.

[Gary Keedwell]

I have been reading some table saw tuning tips and "runout" is referred to with both the blade and the arbor.
I have no idea what this refers to.
Chris..."run-out" is an old machinist expression meaning that the rod (arbor) is not running "true". When you put an indicator on it and spin the arbor ....if the indicator shows no movement...it means it is running true. If the indicator moves , say .003, it means it is running out by 3 thousands of an inch. Hope this helps.:)

Gary

[Chris Yarish]

Perfect guys.
Thanks.

[David DeCristoforo]

"Lateral movement on the horizontal plane in relation to a vertical axis."

Ya... that's what I meant to say...;)

YM

[Greg Peterson]

I'm not a machinist, but I did stay in a Holiday Express last night. :)

[Dave Falkenstein]

Lateral movement on the horizontal plane in relation to a vertical axis.

Is that the same as wobble? :)

[Gary Keedwell]

Lateral movement on the horizontal plane in relation to a vertical axis.
Reminds me of a dance they did in the 60's:D:rolleyes:

Gary

[Tom Henderson2]

Chris..."run-out" is an old machinist expression meaning that the rod (arbor) is not running "true". When you put an indicator on it and spin the arbor ....if the indicator shows no movement...it means it is running true. If the indicator moves , say .003, it means it is running out by 3 thousands of an inch. Hope this helps.:)

Gary

To beat the horse a bit further....

Gary has provided an excellent description. As he describes it, the dial indicator moves from a minimum of zero to a maximum of 0.003 inch ( three one-thousandths of an inch.)

This is often referred to as "Total Indicated Runnout" or abbreviated as "TIR."

If the dial moved from a minimum of 0.025 to a maximum of 0.028, the TIR is the same at 0.003. You get the picture.

Most of the time, the runnout or TIR refers to radial runout at a location on the shaft. But in discussing table saw arbor runnout, we can use the same technique to measure the lateral wobble of the arbor flange. The same techniques and nomenclature is used.

Once in a while you will read where somebody is discussing runnout in terms of "plus and minus 0.001" or something like that. When you see that, be sure you realize that "plus and minus 0.001" is the same as "0.002 TIR."

Forgive the long discussion -- but TIR is frequently encountered and I thought it was worth the bytes to discuss it.

-Tom H.

[Stephen Edwards]

I was just going to ask the same question as Chris and decided to do a "search" first. NOW.....I understand. Thanks folks.

[Glenn Clabo]

It can also be used to troubleshoot...Runout can be repetitive...which is what Gary describes...it has the same irregularity on each rev. Then there's non-repetitive which can be an indication of things like bad bearings.

[Tom Walz]

In saw blades runout could be considered the difference between the nominal kerf , say 0.090”, and the actual kerf, say 0.095”.

Saw plate can be flat within 0.001” Saw teeth can be ground within 0.0005” of one another. If you figure 0.0005” on each side then that is another 0.001”

0.003” is generally acceptable for the blade.

Then you add shaft alignment and bearing wobble.

Runout is measured as saw wobble.

What is really fascinating is big, thin saws where they vibrate as they hit a certain speed. They will wobble side to side dramatically then they will develop a second wobble so that they look like potato chips. Then as the speed progresses, they will straighten out or come apart.

Runout is crucial in gang saws cutting stock for flooring, window blinds, etc. Think of a dozen saws side by side cutting a dozen slats. You will sometimes see saws touch each other and throw sparks.

Runout can also change on smaller equipment but it isn’t as common.

There’s my offering. Not as elegant as Yoshikuni and Greg but a different viewpoint, anyway.

Tom