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Very small screws. Replacing or fixing

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ThunderZed:
I've an electronic device closed by 4 very small screws. My problem is they're very worn and I've to replace them or try to fix them.

I took some measures and the diameter (just the body, not the head) is 1mm (= 0,0394in) and the length is 12mm (= 0,4724in) but only the last 4mm (= 0,1575in) are threaded and a single pitch of the thread is about 0.5mm (= 0,01969in). I don't know exactly what to search on the web, eg. I tried "m1 screw" but I found only M1.2 screws for metal on aliexpress, I mean with different thread (pitch=0.25mm) while I guess these screws are specific for plastic.

I think my only other option is to fix them, I mean I'd use a saw and make a deeper cut on their heads so I'll screw/unscrews them by a flat head screw-driver. In this case I think my main problem is how to keep them enough firmly while I use the saw to avoid to ruin their heads.

Suggestions?

PlainName:

--- Quote ---how to keep them enough firmly while I use the saw
--- End quote ---

Two bits of wood clamping the screws. Usually you'd clamp the wood and drill slightly undersize holes at the join for the screws, but these are so small that just pressing the two bits of wood together would probably have them deform around the screws.

Is that scale 1mm? If so, the pitch doesn't look lik 0.5mm to me but more like 0.3mm, which would match M1.3 or so. The unthreaded part is likely slightly smaller in diameter (so it doesn't snag on the thread if it goes it that far). I would be tempted to get the M1.2 and try it - worst case you're out a few pence and however long it takes to turn up.

jpanhalt:
Wood will probably work as might any stiff plastic or rubber, particularly if you are just cutting a slot.  I would just drill a 1 mm hole in the wood and turn the screws into the hole.  They should fit snugly enough not to be a problem. 

For other work, like turning the heads, I use annealed copper or lead strip in a 3-jaw or 4-jaw to keep from damaging the threads.  That works good for holding gears when you need to bore them.

Gregg:
You could possibly grind or file the worn part of the head flat and silver braze another torx or similar head cut off another suitable fastener.
The trick is to get both surfaces as flat as possible and use as little as possible high silver content silver braze wire.  Test this method on some scrap fasteners to develop the methods necessary.

RJSV:
Funny coincidence, was just thinking as I cleaned up the bench, the Plastic Toys use that size...Approx 12 mm length, and completely flat, under the head. So it seats down fully, not a 'cone' shape.
  The commonly seen 'TOY' screws are 'silver' colored, Philips, fully threaded length.
Exactly my thoughts, concerning what a 'full' bench supply would contain.
Synchronicity, that's common.

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