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Vise pivot.


DanBrassaw

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I was driving around earlier, and this popped into my head. Why is the pivot point on a leg vise located as high as it is? I don't have a good vise yet, and I've looked at some various plans for fabricating one, and those plans all have the pivot point where it is on "regular" leg vises. Wouldn't it be advantageous to have a larger foot, with both the leg and pivot point located there? Then instead of the leg taking all the downward pressure, it would take half (or so, depending), the other half bearing on the hinge pin. The longer moving leg would provide more parallel jaw action. I discussed it with a friend, and the only downside we could think of is more flex possible on the moving arm, from the screw pressure. But with the stock size involved in most vises, I can't picture that being an issue. Any reasons why this wouldn't work? And any ideas as to why the current design is like it is? It uses less material, sure, and weighs less, and perhaps it's just overkill to do it a different way, but since mass seems to be king in a smith's shop, I can't see that being much of a deterrent. :P

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Rule #1: Follow the money.

Most people buy new things based on price point in the market, and comparison shop when they can. Successful manufacturers in the past used just enough material to do the job it was designed for, and no more. (Now they make it look pretty and last just long enough to get past the warranty, so you will come back and buy another one.) That means they can sell it at a price point that keeps them in business. You, on the other hand, can over-engineer anything you build for yourself, because you intend to keep it for the rest of your life.

Iron and especially steel did not get to be relatively cheap until a little over a century ago, and the pattern for leg vises was set long before that.

More to your point, smaller vises were made from smaller stock, were made to hold smaller items in the jaws, be used in a more delicate fashion for filing and such, and the pivot could be higher. And (drum roll please) vise versa.

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Thing is, if used correctly, the traditional design is sufficient. The key is this; Always do your heavy hammering, bending, ect. over the fixed jaw not the movable jaw. Of course, now and then you will have to work over the movable jaw, but be carefull at those times.

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I reckon the pivot area at floor level would get full of shop dust, swarf, and crud rather quickly. Given your idea, I envision a really long spring, but in the early days, high carbon spring steel was very dear. Furthermore, it is easier for a smith to temper a short spring than a long one. The spring exerts pressure immediately above the pivot area, because there is less throw there.

http://www.turleyforge.com Granddaddy of Blacksmith Schools

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I reckon the pivot area at floor level would get full of shop dust, swarf, and crud rather quickly. Given your idea, I envision a really long spring, but in the early days, high carbon spring steel was very dear. Furthermore, it is easier for a smith to temper a short spring than a long one. The spring exerts pressure immediately above the pivot area, because there is less throw there.

http://www.turleyforge.com Granddaddy of Blacksmith Schools


Good point on the shop dust, I hadn't thought of that at all. But I pictured a movable pin to change the parallel jaw width, so it would be easy(ish) to clean out, depending on how heavy the setup was. As far as the spring goes, I don't think it would have to be any longer. To be honest, I've only worked with a post vise once, so I don't recall what kind of tension it had on it, but it only has to overcome whatever friction is in the screw mechanism to work properly, right? The spring could even be mounted lower, as long as it maintained enough pressure to open the vise. I can't imagine it would have to be any longer than usual.
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I was driving around earlier, and this popped into my head. Why is the pivot point on a leg vise located as high as it is? I don't have a good vise yet, and I've looked at some various plans for fabricating one, and those plans all have the pivot point where it is on "regular" leg vises. Wouldn't it be advantageous to have a larger foot, with both the leg and pivot point located there? Then instead of the leg taking all the downward pressure, it would take half (or so, depending), the other half bearing on the hinge pin. The longer moving leg would provide more parallel jaw action. I discussed it with a friend, and the only downside we could think of is more flex possible on the moving arm, from the screw pressure. But with the stock size involved in most vises, I can't picture that being an issue. Any reasons why this wouldn't work? And any ideas as to why the current design is like it is? It uses less material, sure, and weighs less, and perhaps it's just overkill to do it a different way, but since mass seems to be king in a smith's shop, I can't see that being much of a deterrent. :P



It's difficult for modern people to envision the conditions found in blacksmith shops of 150 or 200 years ago. The bellows, anvil and vise were the three most expensive tools in the shop. Tools like vises and anvils were priced by weight (which is why they are marked) and buying a heavier one meant significantly more money. My research into costs back then showed the cost of those three tools often equalling 1/3 to 1/2 of a journeyman's annual wages. By comparison, even $350 for a leg vise today is peanuts.
Another thing to remember is that leg vises are not specifically blacksmith vises. The design of the leg vise was universal for most all tradesmen needing a vise made of metal, whether they did metalwork or not. Leg vises were used in shops of comb makers, eyeglass makers, carpenters, joiners, pewterers etc. etc. Blacksmiths today tend to see all leg vises as theirs, but this isn't the case historically. Lighter versions of leg vises were perfectly good for many of the settings they were used in. In fact, that is one concern- blacksmiths today think that if it's a leg vise it's ok to pound on. Many of the old smaller leg vises survive because they were not subject to rough use, nor were they intended to be. Even a lightly built wrought iron vise would hold up in most settings just fine. A smith might have to buy a heavier one. And even in a smith's shop, lighter vises perform well in the filing and assembly areas and are not subject to heavy pounding at all.
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Just got back from a week of camping out with a couple of forges, medieval anvils and the smallest post vise I own---a 3" *oldie*, (tanged mount, brazed up screwbox and screw, wedged pivot pin, etc, got it last Q-S for $20!), THOROUGHLY chewed out a fellow wanting to POUND on it with a 3 pound hammer; he was used to working on one of my 6" vises and didn't even THINK...My little one survived *this* time.

When I was younger it was all about *BIGGER*; now I'm starting to think that a light weight traveling set up has a lot of merit in it...

Now for my question: using typical methods of the time it would seem easy to skip the pivot plates and just forge weld a second piece on the end of the moving jaw leg to fit around the stationary leg and put the pivot there. Anyone ever seen one like that?

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Not sure what you mean, something like the pivot plates, only secured parallel to the moving leg, instead of perpendicular to the fixed leg? I would think that would be stronger, since the force is only shear at that point, instead of torsional. But then again, I don't know which force iron or welds holds up to better, so I might be totally wrong.

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Well it's a forge weld either way for the older vises.

Let me try to explain it another way: hold the index finger of your left hand up vertically this represents the stationary leg; now take the index and middle finger of your right hand and "clamp" the left one, this represents the bifurcated end of the moving leg. Now drill through all three fingers and insert a steel pin to represent the pivot pin-----strike that last bit and just imagine it!

I guess that the plates typically used on a post vise to hold the pivot pin do act as guides for the moving leg as well helping to keep it from racking in use.

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DanBrassaw

Just like you I intend to build a leg vice. I was fortunate enough to be offered 1.5 meters of round steel 50 mm in diameter (used as a shaft for a massive water pump) and get an acme threaded rod I extracted from a 6 inch valve

http://img189.images.../img1017pq.jpg/

The static leg will be around 87 cm tall and the moving leg will be made with the remaining material. I also intend to set the pivot as low as possible. Among other ideas, I want to fabricate a movable setting for the screw so I can slide it up and down the static leg, according to the job I intend to do. The lower pivot will have several settings, depending on how big a piece and want to work. The jaws will be assembled on pivots so will adjust to the shape of your work. These are the main guide lines, but I have no idea yet on how to assemble the lower pivot or the screw, we shall see.

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Aesthetics and Historicity. I am admittedly a fossil who purchased his first leg vise in 1965. I have become a vise aficionado. I love the appearance of the old vises. I am "design prejudiced." I own six of the tanged mount vises, and I have three of the later solid box Peter Wrights. I don't use the tanged vises, as I consider them antiques. I never thought I would be a collector, but never say never. I use the Peter Wrights. The box/bell turnings on the Peter Wrights and on a couple of the tanged vises is quite fetching.

I got one 2 1/8" jaw bench vise off of evilbay. It is forged like the larger version, tanged English vises, with a few exceptions. The mount has a small, downward "Hook" to dig into a wooden bench top. The tang is a threaded bolt with nut. The fixed leg has a right angle bend just below the pivot with a vertical threaded hole with jamming handle. This tightens it to the bench bottom, there being enough thread for a 2½" thick bench top. The spring was missing, so I forged one, 2 1/8" long. To my way of thinking, it is a pretty little vise, and I wouldn't change a thing.

When the machinist vise came into being with its parallel closure and slide, it may have been cast, but they still followed the lines of the forged jaws, because they were nice looking and functional.

My personal vise is a large Peter Wright, and I see it, in profile, as I enter my shop door. It is a beautiful sight...don't want to change it

http://www.turleyforge.com Granddaddy of Blacksmith Schools

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