Thread: Screw cutter

I'm often doing projects in aluminium that require lots of screws in small sizes such as 2, 3, 4, 5, and 6mm, and often I thread them into the job.
Some projects require a shot load of screws so I'm forever cutting the screws to different lengths with a hacksaw then filing them neat, so I looking at making a screw cutter.

With the last job I did, I tried an experiment which worked really well. Using a piece of steel about 6mm thick, I threaded holes for 3 and 4mm. The steel was clamped in the vice. the screw was screwed from underneath to the the amount of stickout I wanted removed, then sheared it off with a piece of HHS lathe tool and a hammer. Only problem with this is the threads in the mild steel will wear too quick.

So now I want to make a cutter ( something like the pic below ) that works by lever instead of a hammer.
The idea is to thread 3, 4, 5 and 6mm into a block that's hardenable, and near the lever pivot, fit a piece of old jointer blade as the cutter.

Question is : What type of steel for the block ?

Hi Phaser,

Your idea reminds me of the Electricians crimping pliers with the screw shear in them.

But I do like the idea of a dedicated shear. A bit of gauge plate for both parts suitably hardened after drilling and threading.

I would use a piece of hardenable ground steel flat bar. It is usually either w1 or o1 the difference being the kind of quench used. If you are in Melbourne I probably have a scrap of 12mm thick stuff for you.

Originally Posted by BaronJ

Hi Phaser,

Your idea reminds me of the Electricians crimping pliers with the screw shear in them.

But I do like the idea of a dedicated shear. A bit of gauge plate for both parts suitably hardened after drilling and threading.

Prob just need gauge plate for the plate since jointer blades are HHS.
Where do ya get gauge plate from ?

Hi Phaser,

I suspect that in Australia you might not call it "Gauge Plate" ! It is the flat plate equivalent of "Silver Steel". It usually comes in 13" inch lengths and wrapped in anti rust paper. Most of the engineering supply people sell it. Very common in both imperial and more recently metric sizes. Various widths and thickness’s in 1/16" inch increments and now 0.5 mm steps. Available in oil and water hardening varieties.

Some that I have bought, have detailed instructions printed on the wrapper for hardening and tempering the material for your desired hardness. The stuff that I have is "Stubbs" branded. The metric gauge plate I suspect is of Chinese origin, simply because it is metric and only wrapped in brown greased paper without any branding or other information.

If you have MSC there, they sell gauge plate and RSC may as well.

HTH.

Haven't got round to making it yet. Busy here so on the back burner at the moment.
Here's a good design I'm thinking over. : https://www.youtube.com/watch?v=cHjmPUrxtgA

Hi Phaser,

An interesting variant on the electrical pliers/screw shear tool. You could also use a barrel shaped cutter with a straight edge, which would give you an even longer lever and have the threaded holes in a straight line.

Flat ground stock that can be flame hardenend is indeed called gauge plate - I purchased some not that long ago from Hales tooling and industrial supplies located here in Adelaide it only comes in fixed lengths though and I had to buy a 50cm length.

Wouldn't this type of screw cutter destroy the the beginning of the thread? I've used all sorts of things for this job but the only things that work are either a hacksaw or a bandsaw and then finish off on the belt sander.

Hi 4Me,

If you watched the video you will have seen that the screw threads are reformed when removing the screw.

Originally Posted by BaronJ

Hi Phaser,

An interesting variant on the electrical pliers/screw shear tool. You could also use a barrel shaped cutter with a straight edge, which would give you an even longer lever and have the threaded holes in a straight line.

Interesting thought....what would that look like ?

Originally Posted by 4me

Wouldn't this type of screw cutter destroy the the beginning of the thread? I've used all sorts of things for this job but the only things that work are either a hacksaw or a bandsaw and then finish off on the belt sander.

Depending on the screw diameter, I have always used either a hacksaw, a mini hacksaw or a jeweler's saw, then I jam the screw head in the vice and finish by running a fine file around the thread end with the file held at 45deg. That works a treat.
If I make a cutter I will still have to finish the thread but it's the sawing that takes so much time. A cutter will give me more uniform length too.
If you use a grinding wheel, hold the screw pointing down a bit so it drags the thread off the end, else it will mash the threads together and you won't get a nut on.

I cut just about every machine screw or bolt I use cos I'm a bit of a neat freak that way. I won't mix nuts and bolts/screws either cos I want them all to match for looks.

If you have a nut on a thread when you shorten it with a hacksaw, when you remove the nut it straightens any burr on the thread so cleanup with a bench grinder or file is easy. Using a shear tool to cut off the 'extra' thread after it had been screwed into the lower jaw of the shear would effectively do the same thing.

Michael