Material slipping in vise

[CaptainSpaulding]

I was always told by my father not to force things too hard or too tight so I'm always a little afraid to overtighten my vise when I need to hammer something in it.  It's an old cast iron thing that weighs about 75 lbs (with a tiny anvil attached, which I don't use for forging).  I've seen videos where users will actually hit the handle of the vise with a hammer to tighetn it as far as they can but just because someone does it doesn't always mean it's right.  Is there something I can do to keep my material in the vise so tight that when I hit it it doesn't slide down into the it?  Does the "squeeziness" of a vise deteriorate over time?  Is this a case where I should just pound on it until it holds my material? 

 

The red vise is pictured here (although not very well since I was actually taking pictures of the blocks of steel):
 

[bigfootnampa]

What you really need is a good post vice.  That type vice is just not well suited to the type of use blacksmiths put their vices through.  

[Grizzer]

IMO a vise that size isn't going to break from you tightening it by hand.  If you are worried about marring your work (which is much more likely) you can use some brass or aluminum shims between the part and the vice to protect your part's finish.  I have seen people using a hammer or mallet to finish tightening a vise, and have done so myself as needed, but it's not always the most efficient way of doing things. :)

If you are consistently having a problem with not being able to tighten your vice enough, the simplest solution is to make a longer handle for the vice, which will allow you to apply more torque when you tighten it down.  Otherwise a couple taps with a deadblow hammer or wooden mallet won't hurt.

Now, that doesn't mean go crazy with it and put a 3 foot cross bar on it or take a 20 lb sledge to it! :P

[Grizzer]

After pondering on it a bit more, I realized I failed to answer your other question.  Yes, vises can lose their grip over time, as the jaws or the threads wear down, but you will usually see them get loose and have a lot of "slop" in them more than lose their grip, per se.

Bigfootnampa is right in that a leg vise would be much preferred for smithing work, but we can't all have the best gear, especially when starting out, so if this is what you got, work with it.

So far as putting a longer bar on it, I'd recommend going no longer than 50% longer than the bar that was on there originally if you go that route.  I have also seen people use a length of pipe as a bar extension, but if you use too long a piece of pipe that kind of leverage can damage your vise, so I don't recommend it unless you've got some experience under your belt.  Really, I'd think a quick couple taps to lock it in (as I stated above) should be enough.

[CaptainSpaulding]

What you really need is a good post vice.  That type vice is just not well suited to the type of use blacksmiths put their vices through.  

 

 

 I understand the need for an anchored support for hammering and I'm on the lookout for one but are they actually more effective at holding material more tightly?  Do they hold better than a regular bench vise?

[ThomasPowers]

Post vises are *NOT* made of cast iron and so can take a lot more "abuse" they usually have a longer bar on the screw as well.

As mentioned if you have problems with gripping you can make softer vise jaw covers *or* rework the original knurling on the jaws to be more aggressive. I have one postvise with such aggressive faces on the jaws I only use it for cold work and even then usually with a set of jaw covers on it

[Fe-Wood]

How about putting something under the work piece... Like a jack, to keep it from sliding down? You wont stop it from moving unless you give it no place to go....

[bigfootnampa]

 I understand the need for an anchored support for hammering and I'm on the lookout for one but are they actually more effective at holding material more tightly?  Do they hold better than a regular bench vise?

Well when I got my 3" jaw post vise set up I sold my big machine vise (which was at least twice the size of yours).  I sold it because after a while I realized that I'd never use it again.  Now I have a 4 1/2" jaw post vise to set up for the heavy work.  I'd say that even for non-smiths the post vise does EVERYTHING better!

[Glenn]

Put a piece of rubber on the jaws of the vise. Cut a piece of radiator hose the long way, or get a piece of rubber conveyor belt, etc. The rubber will grip and but mar the work piece.

[rockstar.esq]

I would suggest that post vises aren't going to grip harder than a machinists vice all things being equal.  They will however have less stress in the mechanism since the screw bears no stress from downward blows like a Machinists vice does.

 

I'd also point out that the lower pivot of a post vice leads to an arcing jaw path resulting in less jaw contact compared to machinist vices which move parallel.

 

I'd imagine that damaged threads would happen before a vice was sprung.  Hammering work on a machinists vice is more likely to damage it than over tightening.

 

Rosin is often used on gun barrel wrenches to keep them from slipping.  Rosin or hose on the jaws will work only if you're doing cold work.  You might try lead sheets as well.

[thingmaker3]

I would suggest that post vises aren't going to grip harder than a machinists vice all things being equal.

 

The gripping force of a vice is proportional to the applied torque and the tpi of the thread. Same as with any lead screw. To compare any given two vices, look at the ratio of tpi and the ratio of handle length.

[billyO]

The gripping force of a vice is proportional to the applied torque and the tpi of the thread.

 

Hello all.  IMO the big advanatge of the post vice v. the machinist vice is SIZE.  I'm learning that in some things, size DOES matter.  You can get more grip because the handles are most likely longer (more foot pounds of torque) and you can whack on them because that handles are thicker (~3/4" dia) on mine and the threads can take the abuse because they, too are beefier.

 

Mr.bigfootnampa - My first (and only) vice for years was a 4 1/2", until I got a 6" last fall.  I Like it a lot, and have even used my 16# sledge on it a few times.  Only thing that happened was I loosened my concrete anchors so now I have a wobbly vice. 

[Alan Evans]

The gripping force of a vice is proportional to the applied torque and the tpi of the thread. Same as with any lead screw. To compare any given two vices, look at the ratio of tpi and the ratio of handle length.

+1

You can increase torque easiest with a longer lever.

The longer lever is more radical but for an everyday improvement you can put a ball race in place of the washer on the thread spindle. Standard ball races will cope with a few tonnes of end thrust, angular contact or spheroidal roller bearings will obviously do more.