interferance fit on small parts... tollerance help
interferance fit on small parts... tollerance help
(OP)
First off I hope I put this in the right section of the forum...
I looked up the tolerance in some iso charts online for parts .484" in diameter (shaft/hole) that will have interference press fit...
I found on the chart that the tollerance should be between 0 and 1.2 or so thousands for the interferance fit
So I specified the hole to be .4840 +.0000 -.0005 and the shaft to be .4840 +.0005 -.0000 so the interfernce will be right in the iso tollerances
The machinist asked how he could possible measure this... I told him to use his micrometers... he kinda scoffed and said he will make it to looser tolerances and get it to work...
I just wondered if there is a better way to do this that everyone could agree with?
Thanks.
I looked up the tolerance in some iso charts online for parts .484" in diameter (shaft/hole) that will have interference press fit...
I found on the chart that the tollerance should be between 0 and 1.2 or so thousands for the interferance fit
So I specified the hole to be .4840 +.0000 -.0005 and the shaft to be .4840 +.0005 -.0000 so the interfernce will be right in the iso tollerances
The machinist asked how he could possible measure this... I told him to use his micrometers... he kinda scoffed and said he will make it to looser tolerances and get it to work...
I just wondered if there is a better way to do this that everyone could agree with?
Thanks.





RE: interferance fit on small parts... tollerance help
RE: interferance fit on small parts... tollerance help
RE: interferance fit on small parts... tollerance help
RE: interferance fit on small parts... tollerance help
RE: interferance fit on small parts... tollerance help
The machinist is not testing me... he was being serious... unfortunately.... because I was pretty sure measuring those dimensions should not be a big deal...
So basically you guys are telling me to keep my dimensions and tell him to learn how to measure
RE: interferance fit on small parts... tollerance help
There is a lot of information starting on Adobe page 38.
https://
The link should work, if not copy and paste.
RE: interferance fit on small parts... tollerance help
RE: interferance fit on small parts... tollerance help
I went over everything again a little more and changed it a little using the materials you gave me in that last link... my dimensions are now
Hole: .4840-.4847
Shaft: .4847-.4851
I am a little confused on the definitions of "type of fit" as in table 7-9 on page 385 in that link.... as of now I am using an interference fit H7/p6. From what I can gather from the description it is what I want.
I want to put the shaft in the hole and have it so the shaft does not move and it wont come out... Is there someone that can describe a little differently the descriptions of the "locational transition fit" H7/k6 and H7/n6?
It seems when I do the math that there would be a chance of it being able to come out in service if I used at transition fit H7/n6 as the hole would be .4840-.4847 and the shaft would be .4845-.4849
Thanks a lot!
RE: interferance fit on small parts... tollerance help
I'm not sure what your machinist was trying to say. It appears that he intends to make one part to somewhere near the nominal size, and make the other part to fit. Which is fine, if you don't need the parts to be interchangeable.
Mike Halloran
Pembroke Pines, FL, USA
RE: interferance fit on small parts... tollerance help
Thanks a lot for all the input
RE: interferance fit on small parts... tollerance help
Mike Halloran
Pembroke Pines, FL, USA
RE: interferance fit on small parts... tollerance help
RE: interferance fit on small parts... tollerance help
RE: interferance fit on small parts... tollerance help
RE: interferance fit on small parts... tollerance help
Your machinist might have point about how to measure to 0.0005 unless his micrometer as a vernier scale on it, as an apprentice my micrometer was accurate to0.001", see this link:-
http://en.wikipedia.org/wiki/Micrometer.
Secondly you don't say what your application is but normally an interference fit would be selected on service conditions ie external loads or torque, thermal expansion of parts etc.
Can you give us anymore detail?
desertfox
RE: interferance fit on small parts... tollerance help
I did try to explain the fit a little above... I guess I have a hard time describing it because there are no requirements other than it cant come apart. It doesnt have any specific load/torque on it is part of a nozzle that could not be made out of one part as all the angles made it too difficult to make therefore they wanted to make it out of two and join them together. They said that an interference fit would be best and so I looked up the appropriate dimensions and put them on the dwg.
RE: interferance fit on small parts... tollerance help
Also, a line to line fit is not necessarily bad, it depends on the engagement of the shaft and the loads applied to the part (if any).
RE: interferance fit on small parts... tollerance help
Getting the correct "feel" with a micrometer is the problem. If you don't believe take a micrometer out to 3-4 machinist with a sample part and as them to measure the part at one specific point within .0001. You will be surprised by the variation.