Alignment gage for seperated cylinder diameters.

[gageblockhead]

I have an application where two seperated 1.000 x .475dia bored cylinders muct be within .005in TIR. The logical mechanical inspection technique would be to engage a snug fit gage pin into one of the cylinders and rotate the part on the gage pin with an indicator reading the other cylinder runout. Using a CMM is the a simple procedure but I would like to design an alignment pin gage. By taking the smallest toleranced cylinder diameter minus .0025in should represent the .005 TIR in theroy. Of course the actual design would not utilize the entire .0025in and also incorporate the cylinder diameter concideration. I am on the right track, correct?

 

[Belanger]

Technically, your suggestion would not quite be correct, because TIR encompasses form as well as location. Your gage would be OK to check location, but any out-of-roundness would be overlooked.

What is the exact callout on those two bores? Does the print say "TIR" or is there another term or symbol used?

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[gageblockhead]

Thanks for your response. Yes I realize the feature form must be considered as stated at the end of my inquiry. The first bore is .4375 +.0005/-.0000 the second bore is .4365 +.0005/-.0000. The print call out is "two holes must be inline with in .005 TIR". The bores are both 1.000 long and 2.000 apart. The gage would look like a small dumb bell with one diameter produced to .4353 +.0002/-.0000 and the second produced to .4343 +.0002/-.0000. This should create a quick and easy attribute gage inprocess check for alignment.

 

[dingy2]

First of all, I will covert your information to GD&T. It looks like either circular or total runout but without GD&T, it would be circular runout. A lot of shop floor people call it concentricity but it is really circular runout.

One cannot have a hard gauge for either circular or total runout. It must be checked with a variable gauge of some sort and a CMM also may not be appropriate since it only takes a number of readings about the feature.

I would probably use a divider head or chuck and chuck one of the features and zero it out at the end of the feature with a dial indicator. The axis is now set. In other words, you have created a datum. I am now contacting 100% of the surface rather than taking a few readings with your CMM.

Take your indicator (on a stand) and zero up at the lowest point on the circular feature. Rotate the chuck and record your TIR. Perform this measuring action in a couple of other spots and report your worst condition.

Again, one cannot have a hard gauge with a TIR call out.

Dave D.

http://www.qmsi.ca