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Machine screws are slowly working loose
2

Machine screws are slowly working loose

Machine screws are slowly working loose

(OP)
Machine screws are slowly working loose due to vibration on a CNC lathe.
We have now got some stainless steel screws with a nylon thread locking compound which has reduced the rate at which they work loose. I am looking into other products such as locking nuts. Does anyone have any tips please?



RE: Machine screws are slowly working loose

Insufficient bolt preload ("torque"), inappropriate loading condition (torsion, shear, bending/twisting), fasteners inadequately sized for the loading condition, fasteners being relied upon to locate parts in proper orientation (as opposed to using dowel pins or similar for doing the locating and thus relying on the bolts to only do the clamping).

It would help to know "which" screws are working loose, and a picture is worth a thousand words.

RE: Machine screws are slowly working loose

Have you tried Red Loctite and proper torquing?

RE: Machine screws are slowly working loose

This is not my cup of tea but are "keepers" a possibility? If it is ok to add a mechanical way to bind the screw, that may work in some instances.

RE: Machine screws are slowly working loose

i've been down this road a thousand times.

lock washers arent worth a damn, chemical help (lock-tite or similar) is the middle solution that may work.

the best method is to cut off the excess length of the fastener protruding through the hole, and run a saw or grinder across the ends to create a notch. this creates some threads that spread from the nut to the bolt and vice versa across the notch.

the cut should be into the bolt and nut, as if you are trying to cut the nut into two half circles

ive attached a rough markup image

RE: Machine screws are slowly working loose

I will assume these are screws that go into tapped holes and do not have nuts.

You might consider slightly deforming the threads for about 25% of the length, parallel to the shank, starting at the head. This way you can start the screw and run it down without danger of failing it.

RE: Machine screws are slowly working loose

" a picture is worth a thousand words ."

I sincerely hope the OP is not tempted to make a second post consisting of 5000 words rather than a proper post with concise information like -
- fastener size
- fastener installation details ( specified, versus what actually happens on the third shift)
- description of the retained component or secured components
- the operation or circumstances that creates "vibration"
- whether the "working loose" is a new event that just started happening on a previously utterly reliable set up, or something has plagued a new configuration or operating condition from the very beginning
- a couple of thoughtfully chosen well detailed pictures and drawings

RE: Machine screws are slowly working loose

Aircraft solution is to drill bolt head and run safety wire to link multiple bolts together. Best locking washer -- check out:https://www.nord-lock.com/nord-lock/products/washe...={creative}&keyword=nord%20lock%20lock%20washers&placement={Placement}&utm_source=bing&utm_medium=cpc&utm_campaign=Bing_Nord-Lock&utm_term=nord%20lock%20lock%20washers&utm_content=Nord-Lock%20Washers

Walt

RE: Machine screws are slowly working loose

I’ve found the NASA Fastener Guide to be helpful: Link

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