Possible leadscrew nut for light duty machines.

[Neil WyattModerator @neilwyatt]

[Neil WyattModerator @neilwyatt]

This might be a stupid idea, but i was playing with some nylon fixit blocks.

I managed to get an M6 screw into the single hole. After filing a notch in the end of the screw and making several traverses the hole became reasonably free and tidied itself up.

Result? An ordinary M6 screw (without notch) or M6 studding gives a lightly stiff but totally backlash-free nut that could be used under light loads for a 3D printer or grinding machine.

The only downside is that after a few hours stationary it develops a bit of 'stiction'.

Possibly using an undersize taper tap a freer but still usable result could be got. Another option might be working some teflon grease into the thread.

Neil

[Clive HartlandParticipant @clivehartland94829]

Nylon is a strange bit of materiel, you work it and make a part and then it starts to change shape and a block made to size will enlarge slightly.

The answer is to boil it which somehow stabilizes the nylon. How long i dont know!

Clive

[Neil WyattModerator @neilwyatt]

That's interesting. I think the instability is because it's hygroscopic, and newly machined faces absorb atmospheric water. I imagine boiling might 'fill' it with water?

Neil

[S.D.L.Participant @s-d-l]

Posted by Neil Wyatt on 02/09/2014 13:47:38:

This might be a stupid idea, but i was playing with some nylon fixit blocks.

I managed to get an M6 screw into the single hole. After filing a notch in the end of the screw and making several traverses the hole became reasonably free and tidied itself up.

Result? An ordinary M6 screw (without notch) or M6 studding gives a lightly stiff but totally backlash-free nut that could be used under light loads for a 3D printer or grinding machine.

The only downside is that after a few hours stationary it develops a bit of 'stiction'.

Possibly using an undersize taper tap a freer but still usable result could be got. Another option might be working some teflon grease into the thread.

Neil

There is a big discussion here

**LINK**

there might be another thread as well

Steve

[Russell EberhardtParticipant @russelleberhardt48058]

Much better to use Delrin (acetal). It's much more stable and not hygroscopic.

Russell.

[BikepeteParticipant @bikepete]

Re delrin/acetal nuts – there's also the 'Evanut' technique described here (on HSM)… getting a bit more elaborate than Neil's suggestion though.

[Enough!Participant @enough]

Posted by Neil Wyatt on 02/09/2014 15:19:36:

That's interesting. I think the instability is because it's hygroscopic, and newly machined faces absorb atmospheric water. I imagine boiling might 'fill' it with water?

It is indeed …. and for that reason has been banned on spacecraft since the early days. In that case the absorbed water is released in vacuum and the component goes "twang".

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