Run-out of a Long Shaft

No run out per foot is an arithmetic, not geometric definition. The runout is covered by the pythagorean theorem, it is geometric. I'll be back with some straightness info.

BTW, the hardness has nothing to do with it.

BTW^2 WHAT the heck does the diameter's runout per foot citation supposed to mean?

Milo

1Q. It is not Hydraulic system so as to accumulated. The OD tolerance and run-out are two deferent preconditions and should be confirmed independent through entire shaft length. The tolerance value depend from the shaft usage (designer).

2Q. General NO.

a) Because we are not sure for the grinder

b) and not sure for the shaft behavior after grinding

--- We must ''RUN'' the shaft for ''OUT'' checking. Here is the difficulty in lengthy shafts but there are many ways. Ask help from qualified inspector.

"±.001" refers to the diameter at any given point along the length of the shaft.

".ooo5" run-out per foot, .005 per 10' " refers most closely to the straightness of the shaft.

"Could one assume if a centerless grinder held the OD tolerance could one say the straightness of the shaft was also within the tolerance of the OD, .002"?" Absolutely not as these are not the same animal. you could grind the diameter perfect and still have some degree of arc thus the run-out could be out of spec.

a call out on the diameter to be within .ooo5" run-out per foot, .005 per 10'. Question: is this a valid call-out, i.e. how could the run-out accumulate with a ±.001" tolerance on the OD?

The diameter within .ooo5" run-out per foot, appears to be a valid call out because it is very near to 0.05 mm per metre generally accepted for such shafts. But I could not understand the second part of it '.005 per 10' because it not same as .ooo5" run-out per foot.

On your second question, I should say that the OD tolerance and straightness of the shaft are two different things and to be independently measured.

Well my friends, i.e. Milo, Pavlos, Mr. M, & Pritam, all of you had valid points and if I ever decide to build a Nuclear reactor I'd hire you, Mr. Milo to be on the team...wow, that was quite an answer you gave. However, through a colleague in the metrology field, he summed it up with the following:

Rule #1 in the ASME standard. "Size controls form" so in this case the roundness and cylindricity would be controlled as cylindricity effectively controls the straightness you could assume that the straightness would be controlled also. But you mention that this is a run-out tolerance, different story, run-out is a combination of form and location and would have to be datumed (usually to centers or localized areas of the OD.) This would not be controlled by the diameter tolerance.

I do not disagree with what your colleague has said size calling form, but the assumption that straightness is controlled by form is false.

The term in your original query about "runout per foot," I showed that a uniform deflection of (any value really) .0005 per foot has no basis in fact, that callout denies the nature of the camber of the shaft which is geometric.

I have been responsible for straightness on many hundrreds of thousands of tons of bars and am not overly complicating your question.

longitudinaldeflection (runout) is not a function of form.

We did take a radioisotoes (tracers) course as an undergrad, but am not the ASME code guy. Abdel Halim Galala is the expert there.

Milo

Ah, but he includes cylindricity in his synopsis and indeed it would encompass and straightness errors. However without it you would be correct Milo with the stand-alone runout.

In the synopsis.

Appreciate your comment, InspectorK.

So here is my question, do you believe that this 13'1" long shaft will indeed fall within the envelope called for in the synopsis, and if so what is the material that will do so without deflecting beyond that limit over that length in that section?

I am NOT being a wise @ss, I am trying to reconcile my 30 Some odd (mostly odd!) years in the business with the meaning of these words...

Thanks.

Milo

I'll match your 30 years plus 6 working in automotive, aerospace, Nuclear, ordnances, etc. to metrology work in clean rooms working with nano type equipment. The short answer to your question is no, however if datums are established it could be obtainable.

Thanks.

Milo