Making threads lock by machining different... how to do?
Making threads lock by machining different... how to do?
(OP)
I was wondering if there is a best way to go about machining threads different if you want to screw them together and have them deform and kind of lock in place. Same idea of destroying threads to make things stay together just machine them different on purpose so there will be interference fit and the parts will be more difficult to take apart... what parameters of the thread would be the best to change to make this work best.
The threads are #4-40
Was wondering the best way to do this and how to instruct the machinist to do it.
Thanks for any help.
The threads are #4-40
Was wondering the best way to do this and how to instruct the machinist to do it.
Thanks for any help.





RE: Making threads lock by machining different... how to do?
http://www.spiralock.com/
Ted
RE: Making threads lock by machining different... how to do?
RE: Making threads lock by machining different... how to do?
I.e., the experimenting has been done already.
Rolling your own could be expensive, e.g. if you overdo it and induce a delayed failure, or overdo it more and can't assemble the parts without breaking them.
Mike Halloran
Pembroke Pines, FL, USA
RE: Making threads lock by machining different... how to do?
RE: Making threads lock by machining different... how to do?
if a stud (ie bolt and tapped hole) set-up ... helicoils have a locking feature.
if you want to be sure it never comes apart ... weld the nut onto the end of the bolt.
RE: Making threads lock by machining different... how to do?
the closest thing to this setup I would say would be an acorn nut on the end of a 4-40 threaded rod...
I have used ceramic and metallic high temp threadlocker but its impractical because they take a long time to setup and require additional heating to cure right... also the one is a 2 part which is another step.
I would just like to redesign the threads better... I will start looking at the threads myself... to figure what I want to change... I figured this would be something people do often so would be easy answer
RE: Making threads lock by machining different... how to do?
RE: Making threads lock by machining different... how to do?
this does not have a solid mating surface it just threads on the end of a little rod
RE: Making threads lock by machining different... how to do?
I believe that it is M5x0.8 and 10-32UNF threads that are close enough that they almost assemble. This would be an off-the-shelf solution.
RE: Making threads lock by machining different... how to do?
OR, if you really want a permanent assembly, just have the parts made as one piece, from headed wire with rolled threads.
Custom screws in that sort of size in any common material are surprisingly inexpensive, and the typical minimum order of 25,000 or so won't even fill a bucket, so storage space is not an issue.
Mike Halloran
Pembroke Pines, FL, USA
RE: Making threads lock by machining different... how to do?
There is an ANSI/ASME standard for interference fit threads, which is what it is called when you intentionally alter the thread form (pitch, etc.). Here is a link for the official standard ($40 via download) as well as a Google search that includes some free information:
ANSI/ASME B1.12-1987 Class 5 Interference-Fit Thread
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RE: Making threads lock by machining different... how to do?
http://www.taptite.net/taptite/taptite2000.asp
RE: Making threads lock by machining different... how to do?
What materials are you using? Are they at a stress level when creep is possible at 700 F ? Could be to initial tightening preload, or stress from differing CTEs.
If the problem originates with loosening, and that comes from fastener yield, a longer grip length or different material may be needed.
If current must pass thru surfaces clamped by the fastener, the clamping load must be maintained. Any feature that simply prevents nut rotation will not really guaranteed clamping. Using the fastener as a conductor is generally considered a bad idea.
RE: Making threads lock by machining different... how to do?
RE: Making threads lock by machining different... how to do?
RE: Making threads lock by machining different... how to do?
I'm in a similar situation. I like the idea of creating an interference fit with the threads. However, our app is a small thread (10-32), and it looks like that standard only applies to threads .25-1.5" in size. Are you aware of a similar method for smaller threads?
RE: Making threads lock by machining different... how to do?
Initial cost of 5 minutes and 1 set of components.
RE: Making threads lock by machining different... how to do?
mark
RE: Making threads lock by machining different... how to do?