I have an inside diameter (9.928mm UL) that I have to measure that gets a bearing shaft installed into it. I actually refer the hole as a cylinder because it’s about 25mm deep. I have been arguing with the production manager that we can use a 9.928 (a 1" pin won't go into a 1" hole) pin to check the upper limit (UL) because of the interference fit. Even though the pin is a minus (9.926mm) I'm afraid that the holes are still too big.

What is the formula to figure the interference fit and what should be used to determine the actual UL pin to be used.

I have an inside diameter (9.928mm UL) that I have to measure that gets a bearing shaft installed into it. I actually refer the hole as a cylinder because it’s about 25mm deep. I have been arguing with the production manager that we can use a 9.928 (a 1" pin won't go into a 1" hole) pin to check the upper limit (UL) because of the interference fit. Even though the pin is a minus (9.926mm) I'm afraid that the holes are still too big.

What is the formula to figure the interference fit and what should be used to determine the actual UL pin to be used.

Lets see If I understand correctly,

You have a hole that calls out 9.928mm nominal.
The mating part is an interference fit.
You want to use a 9.928mm minus pin to check the upper limit.
you do not state what if any tolerance on the hole size is given.

If I understand correctly, then if your 9.928mm(-) pin fits the hole, then the hole is most likely oversize. I say this primarily because of the near impossiblity of getting the gage pin into a 2.928 hole without locking it up.

As far as a formula etc, I would suggest lookiing in the Machinery Handbook.

Hope this helps.

James

I have an inside diameter (9.928mm UL) that I have to measure that gets a bearing shaft installed into it. I actually refer the hole as a cylinder because it’s about 25mm deep. I have been arguing with the production manager that we can use a 9.928 (a 1" pin won't go into a 1" hole) pin to check the upper limit (UL) because of the interference fit. Even though the pin is a minus (9.926mm) I'm afraid that the holes are still too big.

What is the formula to figure the interference fit and what should be used to determine the actual UL pin to be used.

I think there's not enough information here for us to be able to give you any kind of definitive answer. Some possible contributing factors, in addition to size:

The relative hardness of the materials (shaft and mating part).
The retention requirements
The method of assembly
The control of cylindricity of the shaft and the hole
The degree of perpendicularity of the insertionIn general, it's not unusual in press-fit situations to specify the shaft and the hole as having equal (or nearly equal) diameters. One of the potential problems, though (if it's a blind hole) is that when the shaft is pressed in, material from the OD of the hole might be displaced towards the bottom of it, which can create seating issues. It's also possible in some instances for material to be extruded up and out of the hole (it has to go somewhere), which might also create problems.

The best course of action is to first determine the requirements of the assembly, then evaluate the variation in relative sizes of the hole and shaft. Once you have those answers, it's much easier to determine the best inspection methods, which might include having pins custom-made rather than using off-the-shelf pins.

Good Morning,

I agree with Jim in that you first need to determine how much of an interference fit you need. Here we have some that are .002 press fit, bearing shaft to hole. We chill the bearing and heat the part to do the assembly. As far as measuring the hold for this we have used Comtor gages and digital bore gages. We check each part and collect SPC data with the digital bore gage and a palm pilot.

This bearing is for a water pump that the boys in NASCAR run and we have seen no failures to the best of my knowledge.

Hope this helps.:)

Send this project back to engineering. You are trying to measure a hole for which you do not know the tolerance limits. As Jim has pointed-out, there are multiple engineering considerations that must be determined. Figuring them out is the job of the engineering department, not production or quality.

Once you know the allowable size limits, a standard GO/NOGO plug gage may work in this application. Use the lower limit as the GO size and the upper limit as the NOGO size. Use the Tolerance Calculator (http://www.ring-plug-thread-gages.com/ti-Gage-Makers-Tol-Calculator.htm) to determine the gage tolerance.

Happy gauging.