Electronics > Mechanical & Automation Engineering

Making a nut bigger?

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Here's an interesting problem.

I'm tightening an M6 bolt in to a nut, and doing it up very tight indeed so it can clamp an object. The trouble is that the mount the bolt an nut go it to is 3d printed, and when the bolt/nut start getting fairly tight the nut rips its way through the plastic hex shaped nut sink structure which has been created in the 3d printed part for it to sit in. What was a hex shaped hole in the part gets rounded out by the nut preferring to turn and tear slowly through plastic than be tightened any further.

If the nut were somewhat bigger, then the hex would be against mroe plastic and wouldn't be able to tear through so easily. But an M6 nut is an M6 nut and the outside dimensions are always the same. I've certainly never seen M6 nuts on sale with, say, double sized outer hex measurements.

Any thoughts on ways to "make the nut bigger" and thereby stop it tearing its hex shaped hole in a 3d printed part in to a round hole it can turn within? The printed part is standing up to the compression forces of the claping and everthing just fine, so if I can just stop the nut grinding away its own hole's hex then I'd have everything working.

Here's a picture of an example of a nut sink in a printed part, so my meaning about rouding out is clear:


Use a nut plate.
Many types commercially available, or you could make your own.

A square nut may be easier to find and would be far more resistant to wallowing out the hole it sits in: https://www.google.co.uk/search?q=m6+square+nut&tbm=isch

If that's not enough, consider switching to a cross-dowel (aka barrel) nut: https://www.google.co.uk/search?q=m6+dowel+nut&tbm=isch but they are more of a PITA as you need to check the dowel is rotated to align the cross hole.

David Hess:
Metric tee nuts are available.

I think the problem is the nyloc nut. Try a regular nut and Loctite blue.


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