Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations cowski on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
Tolerance needed for major diameter of 2 11/16 -12 threads
- Thread starter Mech5656
- Start date
- Thread starter
- #3
Thanks. Is there any chart online or some book may have these min and max values?
This is the best I could find online but is not what I need.
This is the best I could find online but is not what I need.
- Thread starter
- #4
- Thread starter
- #5
The typical outer diameter maximum for any thread is the nominal diameter. Tolerance is how much smaller that diameter can be.
In certain classes of thread there is also a required diameter reduction - class 1 threads for example, start off smaller than the nominal and then there is a tolerance on how much smaller yet is allowed.
I think in class 2 and class 3 threads there is no required offset - the max diameter is the nominal diameter.
In certain classes of thread there is also a required diameter reduction - class 1 threads for example, start off smaller than the nominal and then there is a tolerance on how much smaller yet is allowed.
I think in class 2 and class 3 threads there is no required offset - the max diameter is the nominal diameter.
- Thread starter
- #8
NRP99:
Thanks for your response. I meant to ask you about the calculated number for tolerance. To me, tolerance is the total allowable change in a size.
Should it be +0.000/-0.011, +0.011/-0.000 or half and half on each side? Most probably +0.000/-0.011, but curious to know what the standard says. And yes, the calculated number looks higher than what I thought.
By the way, machining and holding tolerance of +0.005/-0.005 is not hard where I work.
Anyway, I ended up putting major diameter (in this case 2.687) +0.000/-0.002 tolerance on my drawing. I believe it is a safe number.
Thanks for your response. I meant to ask you about the calculated number for tolerance. To me, tolerance is the total allowable change in a size.
Should it be +0.000/-0.011, +0.011/-0.000 or half and half on each side? Most probably +0.000/-0.011, but curious to know what the standard says. And yes, the calculated number looks higher than what I thought.
By the way, machining and holding tolerance of +0.005/-0.005 is not hard where I work.
Anyway, I ended up putting major diameter (in this case 2.687) +0.000/-0.002 tolerance on my drawing. I believe it is a safe number.
Mech5656
As 3DDave suggested and looking at figures in ASME B1.1 the basic tolerance is +0 to -tolerance value. So basically the nominal size is tolerated to be decreased from nominal size towards decreased diameter. So +0.000/-0.002 is good if achievable, I think. But why do you want to use these values instead of following standard? Did you ensure that the mating internal threads will be having same tolerance?
Looking at the formula you used, you are considering class 2A/3A threads, I think.
And +1 to drawoh. Machinery's Handbook is must for any kind of help in day to day life of Mechanical engineer.
As 3DDave suggested and looking at figures in ASME B1.1 the basic tolerance is +0 to -tolerance value. So basically the nominal size is tolerated to be decreased from nominal size towards decreased diameter. So +0.000/-0.002 is good if achievable, I think. But why do you want to use these values instead of following standard? Did you ensure that the mating internal threads will be having same tolerance?
Looking at the formula you used, you are considering class 2A/3A threads, I think.
And +1 to drawoh. Machinery's Handbook is must for any kind of help in day to day life of Mechanical engineer.
- Thread starter
- #12
Thank you all for replying to this post. I have to admit that this is turning into a very interesting discussion. This is all fascinating stuff.
drawoh:
The whole point of this post is that this is a rare thread size and is not mentioned in Machinery's Handbook. I am sorry if I was not clear in my original post. That is why I calculated the tolerance of major diameter shown above. Please check your Machinery's Handbook and reply back if you find this thread size. Thanks!
NRP99:
Thank you for clarifying the tolerance limit. The machinist has the locknut (with female threads) that goes against these threads of shaft. He can match the threads so he did not need the class of threads. Usually, we use 2A/2B class of threads. Thanks again!
drawoh:
The whole point of this post is that this is a rare thread size and is not mentioned in Machinery's Handbook. I am sorry if I was not clear in my original post. That is why I calculated the tolerance of major diameter shown above. Please check your Machinery's Handbook and reply back if you find this thread size. Thanks!
NRP99:
Thank you for clarifying the tolerance limit. The machinist has the locknut (with female threads) that goes against these threads of shaft. He can match the threads so he did not need the class of threads. Usually, we use 2A/2B class of threads. Thanks again!
You can specify that tolerance if you want.. but 2 thou on a thread that large, and asking the machinist to 'match the threads' is making your machinist's life more difficult, and your product cost higher, than it needs to be.
If this is a one-off, maybe no problem.. but from the standpoint of taking the right approach, I wouldn't suggest this process as standard practice. Thread standards exist for a reason, and when followed they are unquestioningly reliable.
If this is a one-off, maybe no problem.. but from the standpoint of taking the right approach, I wouldn't suggest this process as standard practice. Thread standards exist for a reason, and when followed they are unquestioningly reliable.
Oh boy, making threads by fitting to a nut.
How long is the nut?
Who made the nut?
I'd require first piece and job lot inspection of the bolt threads to include a pitch diameter as determined by "over wire" measurements, and pitch and thread form proven with a name brand thread pitch gage with good light.
How long is the nut?
Who made the nut?
I'd require first piece and job lot inspection of the bolt threads to include a pitch diameter as determined by "over wire" measurements, and pitch and thread form proven with a name brand thread pitch gage with good light.
Tmoose,
I have called up weird, custom threads, and the machine shops have asked for the mating part so that they could inspect theirs. In productioh, they can always make an inspection gauge.
Of course, people who call up 1.782-31UN threads, do not deserve to go into production.
--
JHG
I have called up weird, custom threads, and the machine shops have asked for the mating part so that they could inspect theirs. In productioh, they can always make an inspection gauge.
Of course, people who call up 1.782-31UN threads, do not deserve to go into production.
--
JHG
- Thread starter
- #19
Drawoh:
You are correct. After searching in Machinery’s handbook 29th edition, on page 1869, I found the above formula used to calculate tolerance of major diameter. So yes, it was there.
Tmoose:
The nut is 6 inches long and the internal threads are 1.75” deep from one side. It also has set screw holes to go against shaft OD. We made the nut in our shop. They were both (shaft and nut) made together. Thanks for replying.
You are correct. After searching in Machinery’s handbook 29th edition, on page 1869, I found the above formula used to calculate tolerance of major diameter. So yes, it was there.
Tmoose:
The nut is 6 inches long and the internal threads are 1.75” deep from one side. It also has set screw holes to go against shaft OD. We made the nut in our shop. They were both (shaft and nut) made together. Thanks for replying.
drawoh - I forgot to add in the multi-start thread option. Considering I have a Monty Python record with three sides, it seems like there must be some similar option - like a single start RH thread and double start LH thread. That way the user has more choice of mating nut.
- Status
Similar threads
- Question
- Question
- Locked
- Question