O2 for vise jaws?

ballen · May 22, 2019

A friend gave me a stack of ground 1.2842 tool-steel plates, still in the soft annealed state (also known as 90MnCrV8 or O2 steel). I want to make some new hardened jaws for my milling machine vise. Is this reasonable stuff to use? Most of the advice I found by searching was to use O1 steel for vise jaws.

If this is a stupid question please cut me some slack, I'm new to hardening, Last year I put together a small oven with a digital PID temperature control that will go up to 1000 Celsius, and since then I have hardened and tempered a handful of parts in oil and water.

johnoder · May 22, 2019

O2 has 0.90 % Carbon content and can be hardened and tempered to anything between 46 and 64.5 Rc

Per Carpenter Matched Tool and Die Steels

ballen · May 22, 2019

johnoder said:
O2 has 0.90 % Carbon content and can be hardened and tempered to anything between 46 and 64.5 Rc

So would this be a reasonable choice for hardened vise jaws? It's a Hilma hydraulic vise, jaws are 40 x 125mm, vise generates about 4 metric tons (40kN) of force.

WizardOfBoz · May 22, 2019

O2 is a good general purpose tool steel. It will change dimensions a bit more than A2, but is cheaper. I would think that if you harden it AND temper it properly it should be a good material for hardened jaws. If you want to get fancy, make them slightly oversized, harden them and grind the faces.

But they make jaws out of mild steel and aluminum. So I think you'll be find with good quality general purpose tool steel, if you want hard jaws.

Cole2534 · May 23, 2019

If you're going to leave them that thick you'll sacrifice some jaw opening, but they would be stout enough to make extra wide or extra tall.

You can also mill some small dovetails into the top and imitate the pirahna type jaws that are so popular now.

Sent from my SM-G973U using Tapatalk

michiganbuck · May 23, 2019

I have ground V grooves in vise jaws vertical and horizontal in vise jaws if different sizes to accommodate round an various shape parts. Yes with V grooves jaws would be more prone to crack at the V so radius bottom.

Also have made parallels (and blocks) with V notch/grooves at sides for the same purpose for use in a vise or for block in on the surface grinder. Handy for end grinding dowels and the like. Grooves in pairs are good for grinding two at a time. Parts set on a side standing shim can work so parts are off chuck. Most often made these with dressing a 45* point on a surface grinder wheel. If needing/wanting a V to be center I would turn the part 180* on my chuck off the back rail.

ballen · May 24, 2019

Thanks everyone for your replies!

Bosleyjr: yes, my plan was to harden, temper, and then surface grind to get them flat and smooth. The stock I have is 10mm thickness, so they would probably end up around 9.8mm thick (about 3/8").

Cole2534: I'm not sure what you meant by "leave them so thick". The dimensions that I gave (40 x 125mm) are the height and the width.

Buck: these are for my two milling vises (I have a matched pair). I have a bunch of other jaws for them already, including ones that have steps and V-grooves. But the plain old flat jaws are not in such great shape. So if O2 steel is a reasonable match, it makes sense for me to make new ones now.

johnoder · May 24, 2019

they would probably end up around 9.8mm thick

So - it that thick enough for screw heads?

My 5" Kurt uses 7/16 socket head cap screws to retain jaws - which are 3/4" thick

ballen · May 24, 2019

johnoder said:
So - it that thick enough for screw heads?

Good question, I better double check. I'm pretty sure that the existing jaws are 12mm (1/2"). But they might be thicker than that.

janvanruth · May 24, 2019

ballen said:
Good question, I better double check. I'm pretty sure that the existing jaws are 12mm (1/2"). But they might be thicker than that.

maybe differential screws could be the answer if they are to thin to accommodate screw heads

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