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3DDave, maybe you can share some thoughts on my problem? Interesting conversation though, I have to say.

Jassco, just out of curiosity, how does the designer determine the permissible runout (or concentricity) at the floating bearing journal? For the main bearings it is more or less standard practice, even though I could never find so far design guidelines or calculations in the machine design...

Please elaborate more on what means in practice "floating". Does it mean that I should orient the part with respect to the primary datum features (not datums, thank you, note taken), and after that adjust the "floating" datum simulator (hope this is the correct term; I meant v-block, roller...

Not sure, I have to perform incoming inspection, in general I don't possess detailed drawings, so most of the time I have to guess how the shaft was inspected. In two-bearings arrangement is easy, but here I started to scratch my head. I would presume ISO, since it is European company.

Sure, I will attach it to the post. It is not 100% accurate, I have removed some specific features due to confidentiality issues, but it is representative for this discussion. Actually it is vertical shaft for multistage centrifugal pump...

@greenimi, well, not exactly since the shaft's working orientation is vertical and inspection at this position is hardly achievable, practically impossible in my case.

Hi all, just a general question how to proceed if we have to inspect long shaft, which is supported not on two, but three (or more) bearings. When the shaft is supported on two bearings the standard practice is to use the corresponding bearing journals as datums and measure runout with regards...

I wonder how he measured the center offset, and can he do it directly on the machine. Because if he has to take down the part to measure it elsewhere, it would be a nightmare to adjust it again in the same orientation, if required. I wonder also how does he deal with tool wear, and does he widen...

@3DDave, in my opinion the machinist used smaller size tool, and widened the keyway left and right until the desired size was achieved. Other than that, you are correct. Are you sure that you didn't add one extra zero on the error? 0,0001 inch equals to 2,5 micrometers, seems quite tight

@3DDave, I agree on the first part, but still I consider having some quantitative value is a stronger argument than just saying "it looks off-center to me". Thank you for the proposal for measurement method, this also came to my mind as an option. By the way, did you check the link I provided...

@Burunduk, the part is quite heavy, and its diameter is above 500mm. This is not an option, unless some portable device is what you have in mind. I found a paper online here: https://www.cmmi.tuiasi.ro/wp-content/uploads/buletin/2015%20fasc%204/L4%20CM%204_2015.pdf, but I could not find such...

@Belanger, either is fine, as long as the offset with respect to bore center plane can be measured, or calculated. Or any other measurement which will prove that the hub-key-shaft assembly is not possible due to wrong manufacturing of the keyway in the hub. The keyway looks off-center, and I...

Bore is 110mm, and the keyway is 28mm wide. Lenght is 120mm. I can make and attach a sketch if this explanation is not clear enough

Hello, Does anyone know how symmetry control of internal keyway can be performed with portable measuring device, and if there is such device at all in existence. I am not interested in the measurement of the width of the keyway, but rather its position with respect to the bore axis, so that...

Thank you for the clarification, as "ground" means also "base", or "floor", it was confusing to me. The "journal" part was clear to me I don't have access to anything fancy, I think I will use steady rest on a lathe to support datum "B", and the left machining center-hole, which should get...

geesaman.d, Thank you for your reply. Could you please clarify what exactly do you refer to as "ground journal"?

Some follow-up, if anyone is still reading. Using V-blocks as measuring setup creates one issue, since two of the controlled surfaces are conical. If you don't constrain axial movement during rotation in the v-blocks, you will get incorrect reading for runout on the conical surface. It seems...

geesaman.d, thank you for all the information. Really helpful

geesaman.d, how do you calculate runout? Is there some standard methodology, or you have some internal procedures?

geesaman.d, what is the range of runout of the impeller mounting surface, and do you take sagging into account due to the weight of the shaft free end? Our tolerance is 0,05mm (as far as I remember, the drawing is not in front of me at the moment), but the sagging alone is more than that...