Replace Any Plastic Nut or Screw Thread With Instamorph




About: Make:Bromyard is a rural makerspace in Bromyard, Herefordshire.

Using nothing more than hot water you can soften Instamorph and then mould it with your hands. Once cool, it is about as strong as nylon!

(Note that it is biodegradable however - a section I've had for about 8 years open to air, sunlight and UV, plus a bit of rain, has recently started to degrade)

Instamorph is one of a small group of plastics that can be moulded and remoulded at temperatures low enough to be hand safe. This, combined with the strength of it, makes it great for replacing some parts, such as the stupidly expensive nuts found on taps, or if you need a truly custom medium strength nut for a thread section. Even really really weird threads can be matched to a nut now, and in under a minute!

Step 1: First, Boil the Kettle...

Ok, so to do this, all you need is a kettle with some water, a mug and the Instamorph. Oh, and of course the thing with the thread that you want to create!

Boil the kettle, and add your Instamorph to the mug. You can re-use it, so don't worry. The picture shows some that we already melted and mucked about with.

Once soft, the Instamorph goes transparent. Fish it out with a fork or whatever, obviously not your fingers if it is boiling water!

Step 2: Mould Around Your Target Threaded Object

Simply mould the plastic around the target metal object. I pulled it into a strip and wound it around, but you can do whatever you like if it is still quite hot, as it melts back to itself and becomes one homogenous lump after a few seconds.

If it is starting to cool, once wrapped, pour a bit more boiling water over it to get it to bond to itself. It won't bond to the metal, so don't worry.

Once you are happy, speed up the cooling process by running it under the cold tap, then give it a minute to cool throughout the mass.

Now, you can unscrew it. Yes, it is as simple as that.

The result is a solid lump that will hold the tap fixed in position. If you need a totally flat base to your nut, you can saw or carefully snip the plastic. Don't get it too hot or it will melt, obviously! However, slight melting won't matter, and you can re-thread it onto the form if you need to.

Step 3: Really Weird Threads?

Yes, this works even for really weird threads.

Here is a coach bolt with a really coarse thread on it, for which there has never been a nut. But there is now!

Again, just wrap the Instamorph around the threaded part of the coach bolt, and let it set. We also used an adjustable spanner to add flats to it, and then we cut off the end with the side cutters. The end result was a tough nut that let us thread and hold these three bits of plastic.

Step 4: Thanks

A note of thanks at the end here to Instructables and Instamorph, who, as part of the "Give cool stuff to makerspaces" program sent us some Instamorph for our build nights in April. Cheers guys! :-)



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11 Discussions


2 years ago

another crud site, make us sign in get our details then do not provide what we signed in for...... crud site stay well clear....... i would love to be constructive but how can i be constructive other than warning others not to fall for you con...

1 reply

Reply 2 years ago

What you talkin' 'bout, Willis?


3 years ago on Introduction

thanks for sharing this awesome idea.. . its really a big help.


3 years ago on Introduction

Cool idea. One thing you might try is to take a socket just bigger than the bolt and imprint the top of the plastic. That way you have a homemade nut that you can drive with a ratchet.


What an awesome use for this stuff! Thanks for sharing this, I can't wait to try it out. I wonder if it would work in the opposite way, for creating a plastic bolt to fit in a threaded hole...

1 reply

Yes, that does seem to work. You might have trouble getting a really solid bolt, but it should be fine for light duty. It tends to bulge a bit and then you can't undo it, but you can wait and re-soften the bulged bit, then undo it. The other issue is, it sort of doesn't fill the void that well on smaller things.

Give it a go and do an Instructable!


Can't say I've tried, but since you can mould it to nearly any shape, & you can re-melt it to stick it to itself, you can likely either mechanically key the surface so epoxy can grip, or use a second bit of instamorph and bond that on for the second part.

Also, there's loads of glues out there, some will work I'm sure.


3 years ago on Introduction

Thanks for this... I have never heard of this stuff, but it sounds very useful.....


3 years ago

It might be photodegrading due to UV exposure, but I don't think it is biodegradable; if microbes can't digest the material, UV light might just be breaking it down into smaller indestructible molecules.

1 reply