Crack repair of hardened precision vise

[Bob_Nor]

Hi together,

I have a repair job to do where I need some advice:

This is a russian precision vise used for grinding and measuring. It came with a quality document that proove it's precision of a couple of µm in important areas.

I made the mistake to overtighten the vise and crack it apart. The crack started from a sharp corner and runs right through one side of the vise.

The vise has been replaced since with a somewhat bigger and stronger model out of chines production. I wrote "Crack" on the old vise and put it aside but found myself using it frequently because it is so handy with it's ground sides all around. I know that I won't be able to repait it to it's old precision but I would like to try to make it usable for less demanding (my typical) work.

I don't want to soften it completely and reharden it because I don't have a surface grinder to get it halfway flat again.

My idea was to grind into the crack coming from the jaw and from the side. Put a c-clamp over the vise to keep everything in shape. Then preheat to ca. 400°F and stick weld with Castolin Xuper 680 S which is intended for welding tool steels. Then cool slowly.

What do you think about this repair attempt?

 

Bob

 

[Cedar Crest Forge]

I wonder why this has not been answered yet, I am sure there are welders on here. Maybe because you did not specify the type of steel that was cracked? I am not a welder, I would most likely give bad advice. Hmm, with those grooves in the handle, it looks like it was meant to be hand tightened, rather than wrenched.

[BIGGUNDOCTOR]

I would TIG weld it myself. A lot more precise. You will have to anneal the weld enough so it is not brittle. Look on the used market for another one, as they are pretty common and not that expensive.

[Bob_Nor]

Thank you for you replies!

These vises are typically hardened to 60 HRc throughout, probably made from medium to high carbon steel.

Stick welding is all I have available. For use on my 60 year old small industrial milling machine I already have a new vise. I would like to use this vise for other things in the workshop a it can be used resting on the ground sides too. It is written off so what ever the repair will manage is welcome - if the repair doesn't work: No big problem.

 

[Frosty]

Drill a hole at the closing end of the crack to stop it cracking farther. Grind it as described and weld it up with Castolin Xuper 680. Your preheat will serve nicely. Just do NOT overamp the 680! Run it at or below recommended amperage it not only doesn't need lots of power to do the job well too much can make things worse.

I used to carry a tube of it in the emergency welding supplies on the drill rig. Back before the original company was bought out, it was called Eutectic 68 Super.(Take THAT aphasia! I remembered writing the last sentence) We broke a leaf spring on the 20' tool van and were far enough out we were looking at going home for a couple weeks till the shop could get a couple mechanics and tools out to repair it. Sooooo, I brushed it clean, jacked it up till I could clamp it even and welded it up. It even ran well overhead. It got the truck back to the local maintenance shop where they okayed it for the ferry ride, that shop okayed it for the drive from Haines to Anchorage. That stupid spring was still on it when it was auctioned off something like 8 years later.

I'm not recommending welding leaf spring but the stuff held and the spring didn't lose effectiveness. Good stuff your repair plans should turn out well if not to factory spec.

Frosty The Lucky.

[Bob_Nor]

Hi Frosty,

thank you for sharing your experiences and this nice story! So I will attempt the repair this way as soon as I find time and report back how it worked out.

Have you noticed the red and black grooves at the sides of the vise? While the vise is very precise in the important dimensions the grooves were cut in in completely different heights. So I made separate clamping nuts for the sides and painted them differently. These russians!

Bob

[Frosty]

You're welcome Bob, that tube of Eutectic 68 worked so well it blew my reputation as a welder WAY above my real skill levels. We'd be out of town and having the truck serviced or repaired in another camp's shop. A routine vehicle Inspection of anything that comes through a shop is expected and someone would inevitably ask who in the Anchorage shop butt welded a LEAF spring. They never asked me they'd ask the geologist, lead man who'd just point at me and not say anything. It was the welding rod, NOT me! Last time I priced it it was running more than $100/lb. IF you bought 10 lbs. or more.

Different height clamp slots eh? Maybe Russian's nuts are a consistently different size on different sides? 

Frosty The Lucky.

[Bob_Nor]

Hi together,

just a short progress report:

I welded the vise as I had planned and heated it afterwards 3x to about 410°F.

It worked well and the vise holds up to being tightened with a wrench.

I want to grind away the sharp crack inducing corners on the other side and remove weld that is above surface level. When I'm finished I will post some pictures as it might help somebody with a similar problem.

These electrodes really seem to hold up to what the manufacturer claims!

 

Bob

[ThomasPowers]

I like the round chainsaw files for rounding inside corners to prevent stress concentrators.  If you need a smaller fillet a needle file may work.

[Bob_Nor]

Hi Thomas,

most areas of the vise is still very hard so a file wouldn't be happy to touch it. I might have a fine stone or a diamond file that fits into the gap to reach the sharp edges.

Bob

[arftist]

Die grinder with a stone bit.

[Bob_Nor]

My first try will be to mount it on my ancient tool grinding machine and to try to remove the superfluous material without harming the useful surfaces.

But I sill haven't done this step.

 

Bob

[BIGGUNDOCTOR]

No surface grinder available? I would guess that as the weld cooled it would pull the jaw out of parallel.  I kept all of my machine shop equipment when I closed the shop in 93. The Clausing 10x16 surface grinder has come in handy a few times.

[Bob_Nor]

a complete regrind of the vise would be uneconomical, even if I had a surface grinder myself. So I try to repair it to a simpler standard that give a usable vise for my typical not too precise everyday stuff. I just have to get rid of some material that keeps it from lying flat and the jows from closing fully.

I will show the result when I have finished the job.