Straightening a small post vise

[DEERESMITH]

Hi guys.

 

I am a blacksmithing, metal working, and old tool  enthusiast, but not necessarily good at it.

I am a mechanic by trade, and honestly better at assembling things that already fit together.

Anyway, I have a little post vise that the dynamic jaw was obviously bent, as the two jaws were very close to each other right where the forcing screw goes through.

It was clear that the static jaw was basically straight, and the dynamic jaw was bent right where the iron wraps around.

I straightened it in the press, without heat. I decided to do this for two reasons. I wanted to maintain the original patina, and I didn't want to risk heating one side more than the other and cause it to twist. (we only have a torch at work, no forge)

I got it pretty straight, but had slight crack on each side, at the base of the wrap. The cracks are not very deep, and they are on the outside of the jaw, right on the thrust washer bearing surface. The cracks are not opened up.

Anyway, when I reassembled the vise, it seams to want to bend back when I tighten it. I am not using a cheater bar, or even pulling excessively hard.

Here are my questions.

Do you think the primary problem is the "memory" of the iron?

If I heat the area up to critical temp, and leave it in the fire and let the fire go out, will that remove the "memory?

If I decide to do that, should I weld the cracks?

And if so, what method? What rod or wire?

This is one of the older vises with the very pronounced chamfering, so I suspect that it is wrought iron.

Thanks,

Kevin

 

[ThomasPowers]

Bending real wrought iron cold is generally a real double purple no-no. Quite likely there is internal damage from both the abuse and the possibly abusive fix.

I'm sad to hear that work doesn't even have a spot outside where you could have piled up a bag of chunk charcoal and used a hair blow dryer to heat it up. I've dug trench forges in the dirt before or used an old BBQ or even kitchen sink before as a forge.

I'd suspect the cracks go deeper than you think and cutting them out and welding with a low carbon welding rod is probably your best bet. Be aware that slag will come out of the real wrought iron and require the use of more filler than you may expect.

and no not memory; wrought iron is often very low carbon and so quite soft and so not much memory. How big a vise is this? It may be quite light duty as the hand made 3" one from the 18th century I bought at Q-S one year...

[DEERESMITH]

The jaws are 3 7/8" wide, and the vise is much lighter duty that the 4" post vise I have. I believe this may be 18th century as the screw box is more primitive, and open on the end. Very pronounced chamfering. It has clearly had a rough, but long life.

The handle is 14" long, and 5/8" diameter. The forcing screw is 1 1/8" diameter.

The parts fit together nicely, but maybe the screw parts are from a heavier vise?

I really feel like I am using the same amount of strength to snug the jaws as I use for everyday use in my bench vise, and the dynamic jaw definitely starts to bend. I haven't tried, but seems like I could probably bend it back where I started if I weren't careful.

The cracks are on the side of the jaws that would be squeezed tighter when tightening the vise, IF THAT MATTERS.

[DSW]

Picts of the issue would help.

 

You say "bend" but what I'm envisioning sounds like a "twist". If the jaws twist when you tighten them, 1st thing I'd look closely at is the mating surfaces where the screw applies pressure. If the mating surface is slanted, I can see that forcing the jaws out of alignment. A simple U  shim might allow you to test that hypothesis. Insert the shim so the base of the U is towards the side that is open more and see if that doesn't cause the gap to close up somewhat.

 

 

At worst you can always make up a slip on jaw insert that is tapered to allow you to apply even pressure. Determine how far out the wide side is, then make the add on jaw that much thicker on that side. Kids at the tech school butchered a really nice Parker vise trying to grind bevel coupons. They'd ground into the jaws pretty deep. I "refaced" both jaws so that they closed evenly and the vise was useable again. In that case, I slipped in 2 new jaw faces, then shimmed them temporarily until I got them touching the whole way across. Then I tacked all the shims in place and welded on the top covers to lock in the alignment. Then I welded everything up.

[Alan Evans]

If the cracks are closing when you tighten the vice it sounds like you created them when straightening sadly. Are the crack surfaces fresh? If not it may have been straightened and cracked in the past. Is it now bending more readily than it did before?

If you weld up the cracks, the other side will then be in tension and depending how deep the cracks went and how far you veed out you may need to plate the inside face to support it. Not very pretty but at least the vice can be used.

I always find it difficult to weld wrought iron unless by fire welding. I keep in mind that it is a bundle of fibres which need to be fused together, a bit like melting the end of a plastic rope to prevent it fraying.

Alan

[ThomasPowers]

The Columbian post vices have open ended screwboxes even as late as the 1940's.

 

Is your screwbox rolled from a sheet and forge brazed together with a forge brazed screwthread added inside?

 

Re welding on the vice:   don't think you could mess things up trying to arc weld it up as it stands...

 

When we fixed my cracked post vise leg a couple of months ago we forge welded it back and wrapped it with a strip of wrought iron and welded that up too.