Quench.

What's wrong with my post vise

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I finally mounted a post vise I've had for years.  The vise closes fine when there is nothing in the jaws.  But if I clamp something on one side or the other, as shown in the pictures, the jaws move sideways relative to each other.  That makes it very hard to align something in the jaws.  Any ideas what's wrong with the vise?  Can you see from the pics if I'm maybe missing a part?  Can this be adjusted?  Thanks!  -Q

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The screw hole on the movable jaw appears to be wallowed out (worn).  Should be round, concentric with the screw.   Without wall support, the movable jaw will move side to side.  The fixed jaw hole looks worn as well and will have the same effect.

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Most of the older post vises were forged, not cast.  It could be that the previous owner(s) did a lot of heavy pounding with sledges on the jaws which, over time, would compress and deform the holes sideways.  Just my guess.

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Use a scrap piece of metal in the opposite side of the jaw so it will not twist when tightened. Saves wear and tear on the vise.

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Greetings Quench,

The problem is at the pivot alignment. Loosen the  bolt and move the floor post side to side. Many times a small shim on the inside of the cheek will correct the problem. If the post is not a fixed to the floor it will also drift and cause jaw alignment problems.. Good luck

Forge on and make beautiful things 

Jim

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3 hours ago, Quench. said:

I finally mounted a post vise I've had for years.  The vise closes fine when there is nothing in the jaws.  But if I clamp something on one side or the other, as shown in the pictures, the jaws move sideways relative to each other.  That makes it very hard to align something in the jaws.  Any ideas what's wrong with the vise?  Can you see from the pics if I'm maybe missing a part?  Can this be adjusted?  Thanks!  -Q

 

 

 

 

The screw hole can be re-bored and sleeved. 

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Yes, you are missing a tool, one that you need to make, but not a piece original to the vise. Clamping anything eccentrically in the jaws will do that without an equal thickness of spacers on the other side.

set of vise spacers on a rod.JPG

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Well, without hijacking the thread with a (forbidden) link to a (copyrighted) catalog photo, I work with whatever I find available.

Attribute the photo above to Gentleman Jim Coke, too late to edit my post now.

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I had the same problem when I put mine back together.  Like Jim Coke says, tighten the pivot bolt, and make sure that part of the vise is as tight as it can be without binding.  Hopefully that is all that is needed.

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Making sure the cheeks of the pivot area are smooth, and aligned is important.  Be sure to grease them as well.

As mentioned having a set of jaw spacers  is a good thing.  The "lots of little pieces to build up to the right thickness" is a great way to go.  

Another method is to take a handful of short pieces of the standard sizes stock you are working and to hacksaw down an inch or less in the middle of the top and then heat and fold the tabs out to a T. I also stamped them with the size as students seem to have an issue differentiating 1/2 from 5/8 by eye.  For my smallest ones 1/4" or so I spiraled the top instead of sawing.

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It is worth pointing out that ALL vices do this, be it old well worn blacksmiths leg vices (that's the vice that's old and worn not the blacksmith or his leg,,,,) or brand new accurtate engineering machine vices. Not shimming exasperates the problem over time.

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When I went out I found that the tool bucket with my vise/vice spacers had managed to get some water in it---odd out here; but as I was firing up the forge anyway I heated and brushed them and rewaxed them and put them up on a shelf in the toolshed while I was making another batch of large tent stakes and some christmas chili peppers and getting back into the swing of hammering as I haven't been doing much smithing since my concussion.  (I pointed out to my wife that the website said I was not supposed to cook or drive  until the Dr said so but nowhere did it mention *blacksmithing*!!!!!!!!!)

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As far as 'all vices do this' ... not so.

If you clamp something out of centre in a vice, any vice, this creates a lateral force because the point of contact is not in the centre of the jaws aligned with the screw, but on the side.

The vice deals with this lateral force according to how it is made. A parallel engineering vice, has the moving jaw mounted on a long and precisely machined guide that does not allow for much lateral movement. Furthermore the touching surfaces are wide and long and can withstand a lot of lateral pressure without a problem. The lateral force will produce a slight torsion on the moving jaw, that will make it flex very little or if the force is strong enough, brake it.

On a post vice, there is no such precise guide. The post vice is built to withstand a lot of abuse and is made with a lot of slack. The lateral force produced when clamping out of centre forces the screw against the body and the touching surface is much smaller than in an engineering vice.

The result is much more wear of the surfaces and a lot of force against the body in that point resulting in wear and deformation.

Eventually the jaws develop a lot of lateral slack and it is no longer possible to clamp something out of centre like in this case and a spacer becomes necessary. But that is not how the vice was when it was new.

A sleeve will return the jaws to their centre. The use of a spacer will keep them centred for another 100 years.

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Thank you all for the thoughtful and helpful replies.  Sorry to not reply earlier; was at the forge much of the day, trying to beat the rain (made it), and form a couple dragon heads for gifts. They're terrible.  Clearly past my limited experience level.  The little crosses I did last weekend were so much easier.  Anyway--getting off track--I was fighting that vise the whole time.

One side is not as bad as the other.  I didn't think about putting something of similar thickness on the other side (duh).  I'm not sure how I would have gotten that piece in place without three hands.  Thomas' T-shaped spacers would help that, and now that I'm thinking about it, any similar sized spacer would help.

I'm going to do a bit of studying of the probem.  I was thinking that maybe a small section of 2" pipe, cut lengthwise, would form a couple of C-shaped shims (looking at the pipe pieces on end).  But first I'll see if I can find anything needing tightening.  And add T-spacers to the to-do list.  Going to have to take a rest though.  Tennis elbow really getting bad.

-Q

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The T shape is nice as they will stay in place with the vice open enough to put the workpiece in place.

(As to what I have done to myself---that's still an open question.  Since last January I have had 4 incidents where I have passed out one of them I fell and hit my head bad enough for a little TBI.  I thought they were hypoglycemia associated with my Diabetes; but my Endocrinologist and my Neurologist both say they don't quite look like that.  Until they get it figured out my wife has to drive me to the border and pick me up each work day.  If the testing was done this month it would be free to me as the 4 ER visits and the hospital stay maxed out my insurance deductable.  If it gets pushed to January I get to cough up another $8K; guess which way the insurance company is leaning!)

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Bummer, each time I look into your health insurance system I decide to stop complaining about ours.

Drink plenty of water, take it easy and watch what you eat.

Did they mention TIA by any chance? Do you have a desk job? What's your blood pressure? Anyway, I'm sure your doctor will tell you what's best to do. You really didn't need that knock on the head.   

I had a TIA last year, stress related, neurologist couldn't see any damage but they can't see any damage in 30% of cases anyway. Decided to care even less than before about work. :)

Hope you get better.

M

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Everyone already covered the problem/ solution for this thread - But I wanted to add a problem I had on jaw alignment. My current post vise gave me fits when I first acquired it and set it up. The problem turned out to be the spring - it was slightly bent (twist). As I tightened the vise down - the jaws would shift out of alignment before they even came tight.  After I flattened the spring and squared it up - My post vise worked great.

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7 hours ago, tdriack said:

Everyone already covered the problem/ solution for this thread - But I wanted to add a problem I had on jaw alignment. My current post vise gave me fits when I first acquired it and set it up. The problem turned out to be the spring - it was slightly bent (twist). As I tightened the vise down - the jaws would shift out of alignment before they even came tight.  After I flattened the spring and squared it up - My post vise worked great.

Ah, thanks, that's one to check too.  I've not taken the vise apart, since it all seemed operational before.  I don't think mine goes out of alignment with nothing in the jaws.  But this is good to have in the thread in case someone else hits it.  Thanks again for great suggestions.

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Thomas,

Please get well, we need you! Seasons greetings by the way.

Göte

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17 hours ago, Smoggy said:

Not shimming exasperates the problem over time.

Actually, not shimming exacerbates the problem; vocabulary mistakes exasperate Grammar Hammers.

11 hours ago, ThomasPowers said:

(As to what I have done to myself---that's still an open question.  Since last January I have had 4 incidents where I have passed out one of them I fell and hit my head bad enough for a little TBI.  I thought they were hypoglycemia associated with my Diabetes; but my Endocrinologist and my Neurologist both say they don't quite look like that.  Until they get it figured out my wife has to drive me to the border and pick me up each work day.  If the testing was done this month it would be free to me as the 4 ER visits and the hospital stay maxed out my insurance deductable.  If it gets pushed to January I get to cough up another $8K; guess which way the insurance company is leaning!)

Feel better soon!

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I'm not familiar with that term Tubalcain2, but I summise it refers to the rebufal of my statedment, which in the 3rd paragraph confirms my statement as true.

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