Aligning a threaded shaft connection 4

[smarte]

Hello,

I want to design a shaft connection using a threaded bore and threaded shaft end to transmit torque. I want to have a straight parallel interferrence fit (on the shafts) above and below the thread to accuractly align the shafts. Does any one have experience with this kind of connection or know of any availible standards.

Thanks,
Sean

 

[desertfox]

Hi smarte

I have missed something here I thought the interference fit would be formed by the larger shoulder diameter behind the male thread and the larger bore in front of the female thread.
Earlier you stated the interference would be between 0.5 and 1.5 thou, theres a lot more than a thou between 1.390 and 1.4375.
Could you please explain as I am now confused.

Regards

desertfox

 

[smarte]

DesertFox: There are two interference diameters on each shaft, one before and one after the thread.

 

[desertfox]

Hi smarte

I reccomend you only have one interference fit on each shaft. If you try to have two one before and after each thread you will have alignment problems on assembly due to the fact that the interference fits will fight against each other unless they are perfectly in line and concentric
which will be very difficult in practice, this doesn't include alignment of the threads either.
You say your torque requirement is low I cannot see the need for two interference diameters.

regards
desertfox

 

[zekeman]

Looking at all these posts, I think the author is being poorly served by many and that obviously he wants to invent a new method for joining two shafts which is routinely done by standard methods. The method proposed is ridiculous for a number of reasons, even after provision has been made for thread clearance.
1)You are "pressing" the two shafts by rotating the threaded parts, so the axial force is delivered by the screw threads,along the helical parts which will in general put an eccentric axial force on the two shafts, making it virtually impossible to cause the press fit without significant deformation.
2)In effect you are trying to cause press fit by rotating the two mating interference parts, another imposssibility
3) And if he manages to do it, he is virtually guaranteed two nonaligned shafts that are cold welded , not what he was looking for
4)And how does he dissasemble it? Another impossibility

In summary, think he should be strongly discouraged from this misadventure and get him to consider standard practice (which some of you are) and not continue to entertain new methods (fraught with difficulty) for an old problem.

 

[JJPellin]

I agree. We seem to be adding a lot of complexity to a simple problem. In a refinery, we routinely couple threaded shafts up to 3600 rpm and 1000 HP with very simple threaded couplers. Unless the assembled run-out required is extremely low, the simplest answer is probably the best.