Best/easiest way to cut small screws

#1

What’s the best and/or easiest way to cut small screws (specifically M3) whilst retaining thread integrity, so I can still add & remove nuts?

Currently I’m adding a nut to test/re-establish the thread after cutting. Then chopping with an angle grinder on a chop frame, which is non-portable and seems overkill.

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There’s electrician’s side cutters with 3.5mm pattress screw shears available. Would those work?

Are there 3mm, adjustable or multi diameter screw shears available?

Or is there a tool at SLMS which would do the job?

#2

Like you I often put a nuts on the thread, this is definitely the fastest way I’ve found to restore the thread. The challenge with an angle grinder is that it cut by abrasion so it leave a big burr. I usually use my dremel cutting disk if I have a lot to cut or a normal hacksaw often work as good (if your blade cut well)

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Alternatively you can use a good cutter and if you cut in one quick go it produce a pretty clean cut that require minor post processing

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Ofcourse you can still use a dremel mounted rotary file to debur it quickly but it’s a pain with a small m3

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#3

I do it the same way but instead of a dremel used metal hand saw.

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#4

Thanks for the super prompt and useful response.

I forgot to add that the angle grinder produces an excellent clean cut with a small burr on one side which I remove quickly with a small file, before removing the nut.

I suspect that if I could properly support both sides of the screw then the burr would be reduced or removed entirely.

I currently grip the thread end in the grinder stand vice with a small piece of wood.

I’m very happy with the result, I’m just looking for a portable solution, so I’ll try the cutter method you suggest

#5

Actually, I think the handsaw maybe better because I need fairly accurate lengths (within 1mm)

Where do I get good hacksaw or metal handsaw blades?

I’m assuming the more teeth the better?

I’ll probably test the 3.5mm pattress screw shears because that would be the fastest, if it doesn’t deform the thread too much

#6

I use a fret saw. There’s still a tiny burr which is easily filed down and I never had a problem getting nuts on afterwards. Accuracy can be quite good too, as the blade is so small it can be started in any chosen thread.

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#7

Is that also called a coping saw?

@Jonty_Bottomley what saw & blades do you use for your coins?

#8

A fret saw is much like a coping saw except the blades are finer and are usually on a fixed mounting.

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#9

Fret Saw / Jewellers’ piercing saw, they tend to be pretty interchangeable names for the same thing.
As described by Doug the main differences are:
Coping saw blades are significantly deeper and have a pin through top and bottom which is mounted grooves in free moving handle and top end piece. Tension is applied with the handle and the blade can be oriented in any direction.
Piercing saws are slightly different in so far as the blades are clamped in place with thumb screws and in most basic saws can only face either forward or backwards. Some fancy saws have indexes at ±45 to get around issues with depth of cut etc. Tension is applied by squeezing the saw frame while clamping the blades.

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#10

If you don’t need a portable solution, you could hold the bolt in a lathe chuck (probably by a couple of nuts again) and cut the end with a grinder/saw/dremel/whatever… This should give you a better finish, no need for filing. A dremel mounted on the support would probably do the best job :slight_smile: If you need to shorten a lot of bolts, I recon it’s worth making some kind of quick-release fixture/jig for the job too.

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#11

Please consider using the nuts and clamping it in a vice rather than a lathe chuck… :+1:

#12

Thanks for all the great advice.

Portable is the ideal. I tried the electrician’s 3.5mm pattress screw cutter and it works quite well leaving a small burr to be filed off.

I’m going to try some rounded wire/cable shears. Are there any in the space?

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#13

The whole point is to spin the bolt while cutting it :slight_smile:

#14

How so? I thought you would spin the nut off after cutting to fix the threads…

#15

That as well (if needed at all), but the nuts would be there to hold the bolt centred in the chuck, close to where it needs to be cut - holding it only by the head would most likely result in the bolt slipping out while cutting. This is more of a quick&dirty solution in case you have a lathe that is too big to grip the tiny bolt directly by the thread, which could also damage it… Another option is to grip the end of the thread that is not needed (if there is enough length) - but then you’re left with a bit of material that may need removing… :slight_smile:

#16

I’m getting close to a portable solution.

So far an electricians 3.5mm screw cutter and small hand file does the job, with a nut in place to fix the threads.

I’m going to try the curved cable shears I mentioned above