Set screws keep coming loose on stepper motor coupler.

Thread Starter

spinnaker

Joined Oct 29, 2009
7,835
If you do not already know, I purchased one of those cheap Chinese CNC engravers ro experiment with engraving PCBs.

On one of the stepper motors, the set screw in the coupler from motor ro shaft keeps coming loose. I need to tighten it every few runs. I thought about some locktite to fix it but I am worried I won't be able to get the screw back out if need be. The screws are pretty tiny.

Any ideas on the best way to fix this?
 

jpanhalt

Joined Jan 18, 2008
9,670
Loctite is color coded. There is a very firm, green version that requires heat to remove. I suspect any of the red versions will work for you. "Permanent" is only relative and depends on the fastener size. I would have no problem using a red permanent version in your application. Worse comes to worse, you can use heat to remove the set screw.

John
 

Thread Starter

spinnaker

Joined Oct 29, 2009
7,835
OK locktite or nail polish?

I thought about nail polish put where the screw sits it might be a little difficult to scrap off. Though I suppose I can get a screw driver in there.
 

Thread Starter

spinnaker

Joined Oct 29, 2009
7,835
As an additional aid, if the shaft is round, you might consider filing a flat on it or drilling an indent where the set sets into it.

John

Was going to ask that too. It is round.

Another thought I had was to put a dab of nail polish on the shaft where I intend to put the set screws. Let it dry first of course.
 

#12

Joined Nov 30, 2010
18,210
put a dab of nail polish on the shaft where I intend to put the set screws. Let it dry first
Too brittle. No grab.
It works for an outside coat, or a thread lock, but it won't work for a point controller.
It scrapes off easy because it is too brittle.
 

#12

Joined Nov 30, 2010
18,210
So would you suggest filing the shaft a bit then?
Yes. A flat on the shaft has saved many a drill bit for me.
But you might use a grinder. Tool steel (drill bits) can be difficult to file.
If you're on a motor shaft, that's, "mild steel". A file will work.
 

Thread Starter

spinnaker

Joined Oct 29, 2009
7,835
You can also get Allen set screws with a pointed end they grip better than the flat ended style.
Max.

That is what these are.


Actually just look at them again . They are mode flat. Where do I get the ones with the point? How would I know what size to use?

What are they actually called?
 
Last edited:

cmartinez

Joined Jan 17, 2007
6,992
Blue is the soft thread locker.
I used some red on a guitar jack and I had to use a grinder to cut it off.:mad:
The only way to loosen a bolt that's been locked with red loctite is to heat the part with a small torch.
I like using the type used for cooking desserts, like creme bruilé
 
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