Broken toolmakers clamp.

Remember when I was at Tech College we had to make various tools, toolmakers clamp, punch, scriber, cold chisel all come to mind although that was 60 years ago, time flies. Dave W

Your of course quite correct Duncan, and after you pointed out how I phrased it, I most certainly should have done so in a less confusing way. I meant that for how some think about steel in general. Stronger meaning the ability to resist those bending forces. I should said it doesn't make it stiffer as you did. Hardening to the correct level for the expected use does increase the steels impact and wear resistance so yes in that way it is stronger.

It's stronger full stop, EN8 normalised has UTS 35 tsi, heat treated can be as high as 55 tsi. The yield stress also increases. These figures from a United Steel Co handbook which is about 50 years old.

Case hardening won't change the strength much at all as it's s only skin deep (sorry)

So if a higher UTS [ultimate tensile strength] is quoted, will it have a higher resistance to bending, as in Toolmaker clamp usage? I'm not sure but I don't think so. We may be going down a rabbit hole with this one guys.

Tony

I've found they snap at the side of the hole long before there is any sign of bending. Though the one I made at school is still going strong, just a couple of bought cheapies that are in bits now.

Edited By JasonB on 25/09/2023 18:50:39

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Could you share a photo, and/or drawing, of that please, Jason

… stress-raisers are a subject of interest.

MichaelG.

I'll see if I still have the broken bits in the morning.

Mine broke in exactly the same way as Jason's. But I think that its partly a design flaw, the jaw of this 2" one being too thin for the thread size. I know I bought it at a steam rally some time ago, but forget from who. My 2.5 " ones from Machine Mart are considerably thicker and have been fine.
I now have made 3 plus repaired the broken ones.
One with 8mm sq jaws, one with the T addition creating one narrow jaw, and today I started making ones from 12mmsq, but with tapers on 3 sides of the jaw, the side ones being slightly concave, almost coming to a parallel 4mm near the tips. This was my original thought, Jason steered me back to this idea.

So I have a selection to play with now. All made from mild steel.

Thanks for all of the comments
Keith

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Thanks, Jason

MichaelG.

FWIW, I broke one in just bthat way, a skilled friend rewelded it, and i have now lwearned not to be so brutal.

The scaffold pole has become redundant!

Howard

Edited By Howard Lewis on 25/09/2023 22:22:29

A couple of not too good photos for Michael

The jaws are 8.8mm square and the clearance hole for the 10-32UNC thread is 5.1mm. A file test suggests the metal is harder than just untreated mild steel so may have had some form of heat treatment or just be a higher carbon steel.

The dark area suggest one side partly fractured prevoiusly and the brighter where it finally gave up

Another clamp is showing a crack down one side

Many thanks, Jason

… Much appreciated

MichaelG.

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Edit: __ although the surface detail is a little blurry, it’s quite evidently a brittle fracture … suggesting excessive and poorly controlled hardening.

Edited By Michael Gilligan on 27/09/2023 10:22:02

Hi, I have a fair few of different size ones, that look like the same make as JasonB's ones, and I haven't managed to break any of them, yet! I also have a 4" Moore & Wright one that was made in at least 1968, as it has some-ones name and 1968 engraved on it, which was given to me. In the photo below, you can see one of my cheap 3" ones in front of the 4" M&W one. Looking in my old M&W catalogue, the size of my M&W one is as given in the catalogue, within a few thou, the 3" cheap one is also close enough to the 3" one given in the M&W catalogue, but the main thing is that with both of these, is the ratio between the diameter of the screws and the size of the jaws, is for all intent and purposes, as near as being exactly the same, the only difference that may have any bearing, is the M&W screws are a finer pitch.

The only thing I can't say, is whether the quality or the grade of material is the same. But I have used my cheap ones, with a tommy bar in the holes, just about every time, to get a tighter grip

Regards Nick.

Edited By Nicholas Farr on 27/09/2023 11:43:35