Thread Class/Fit question
Thread Class/Fit question
(OP)
Does any one know if threads that are the same size and pitch but have a different class designation still fit into each other? Say I have a 10-32 2A thread would that mate with a 10-32 1B or 3B hole?
I would assume that since 1B is the "loosest" designation that a 2A or 3A might fit into it, but not the other way around.
I am asking this question because I am trying to determine the thread of two components and I am uncertain as to what they are. I measured the major diameter to be 11.00mm and the pitch to be around 0.75. So I thought great its a M11 x 0.75 and bought a tap to help me confirm. The tap I purchased is an M11 X 0.75 - 6H. The tap fits just a little loose when I put it in the female portion. But when I taped a new hole in some scrap I had, the male piece did not fit great. It threaded in fine for two turns but after that there was so much interference that I could no longer turn the male piece.
Either my thread class is an issue or the pitch is custom and not a standard size.
Any one have any experience with mixing and matching thread classes?
Thanks
Kyle
I would assume that since 1B is the "loosest" designation that a 2A or 3A might fit into it, but not the other way around.
I am asking this question because I am trying to determine the thread of two components and I am uncertain as to what they are. I measured the major diameter to be 11.00mm and the pitch to be around 0.75. So I thought great its a M11 x 0.75 and bought a tap to help me confirm. The tap I purchased is an M11 X 0.75 - 6H. The tap fits just a little loose when I put it in the female portion. But when I taped a new hole in some scrap I had, the male piece did not fit great. It threaded in fine for two turns but after that there was so much interference that I could no longer turn the male piece.
Either my thread class is an issue or the pitch is custom and not a standard size.
Any one have any experience with mixing and matching thread classes?
Thanks
Kyle





RE: Thread Class/Fit question
Any other combination will have clearance.
This may not apply regardless of length though - for long engagements you may face an issue but it's been a long time since I flicked through ASME B1.1.
Of course if you're talking metric that's not class 2A-2B type fit per B1.1 and I'm not familiar with the metric spec.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Thread Class/Fit question
11mm is an unusual diameter so could it be 7/16" x 32 tpi although I cannot find such a thread in my ref book so it may be a special. Another thought is that your sample has got streched and so elongated the pitch.
RE: Thread Class/Fit question
If the torque increases as the male thread is engaged, then the pitch is wrong.
This is assuming that the male thread is straight.
RE: Thread Class/Fit question
I would get a pitch gauge and measure pitch. Just because the tap fits loose, you may have a 0.8 mode thread for example. So look up the pitch possibilities given your thread size and measure pitch with a gauge, not another tap.
So I think it is your method that gives you the problem at hand.
Regards,
Cockroach
RE: Thread Class/Fit question
RE: Thread Class/Fit question
According to the image on page 2 here the largest 2A external thread pitch diameter would always have some clearance with any internal thread. 1B, 2B, or 3B.
http://www.fastenal.com/content/feds/pdf/Article%2...
RE: Thread Class/Fit question
RE: Thread Class/Fit question
In the UK M11 is not a preferred first choice thread size, it jumps from M10 to M12 although both these threads can both have a 0.75mm pitch, are you sure its a metric thread?
http://www.roymech.co.uk/Useful_Tables/Screws/Scre...