About once a week I get a call or e-mail from someone who just found this site and they start off with something like this: “Hi, I just broke my vise and I’m looking for something bigger to replace it” or “I just broke my vise and I’m trying to find replacement parts for it.” If they haven’t told me already, I’ll ask what kind of vise it is, and what they were doing when it broke.
There are several common responses, but they tend to fall into three main categories. First up is the inexpensive, imported vise that simply breaks during normal usage. These are usually your typical $50 specials at a big box store that have no name on them, but look pretty substantial. Second is a more expensive imported vise, often sold by a U.S. company that you might recognize, and the vise fails doing something that obviously puts additional stress on it. Third is the quality U.S. vise being used for something it simply should never have been used for in the first place.
So, what are the things that damage vises?
The #1 thing you can do to break your vise is put an extension on the handle. Most people call these “cheater pipes” and they slip over the handle and give you additional leverage. Think about that idea for a second….you’re cheating. There’s a reason vise manufacturers limit the length of the handle, and it’s not to make them fit in the shipping container better! They limit the length of the handle so you can’t overload the vise and break something. If you can’t use just the handle and get the vise tight enough to hold the work piece properly, something is wrong.
The #2 thing you can do to break your vise is use it like a press. I can’t count how many times people have said “I was using the vise to press in a bearing when it broke.” Vise aren’t presses, and they aren’t meant to be used that way. Sure, if you want to press in a really small bearing in a really big vise it probably won’t be a problem, but where’s the limit? How do you know when you’re near the limit? Actual presses are built in such a way that the structure can withstand more pressure than the system powering the press can provide so the chances of breaking them are very small.
Why do vises break when used as presses? Look at a vise from the side and try to imagine the forces involved. When you turn the handle it moves the two jaws closer to one another. Those jaws are several inches higher than the center of the screw you’re turning with the handle. The distance from the center of the screw to the center of the jaws is an arm to us a physics term. Because of the offset (arm) between the screw and the jaws, the force applied isn’t just horizontal, it has a vertical component as well. A vertical component wants to shear the jaws off the top of the vise! Obviously, those factors are taken into account when the vise is designed, but vise manufacturers aren’t designing vises to be used for anything other than holding a work piece securely.
Here’s a picture of a vise that failed while being used as a press. I have to say, I really felt bad for the guy who owned it, but just looking at this picture shows how much abuse the vise had seen long before it broke. After seeing the picture I was a bit surprised when he told me it was the perfect shop vise for him, and that he was devastated when it broke. Note how the static jaw insert is missing, and the entire jaw support shelf has broken off. We’ll get to how that happens later, so keep that in the back of your mind. Also, keep in mind that this is a Wilton 1740 which is a pretty small vise at around 35 pounds.
In reality, causes #1 and #2 are often combined when a vise breaks, so if you’re going to try using your vise as a press at least don’t use a cheater pipe on it! If you ignore all of the above, and wind up breaking your vise, just make sure you take pictures and send them to me in case it might help someone down the road.
The #3 thing you can do to break your vise is to hammer on items it’s being used to secure. As above, look at the profile of a vise from the side. They are built to compress from front to back and are generally built in a horizontal plane to deal with those forces. If you secure something in the vise and then hit it with a big hammer using a downward swing, what’s absorbing all that force? Some vises have a support ledge for that purpose that the slide rides on and others have nothing there. Technically, the ledge is called a “dynamic support” because it supports the slide which is a moveable/dynamic part. Even among vises that have a dynamic support they can vary greatly in size and strength. The most severe kind of abuse to the dynamic support comes when someone mounts something in the vise and rests it on the top of the slide. When you look at a used vise and see the dents on the top of the slide, that’s how they happen. The jaws are holding the piece securely, but most of the force is being transferred to the dynamic support through the slide. With a big enough hammer, and a hard enough hit, the dynamic support can shear off. If the vise doesn’t have a dynamic support it will often break the main body of the vise where the slide enters.
The other thing absorbing hammering forces, at least on some vises, is the shelf that the jaw inserts often sit on. In the picture above you can see the front jaw insert in place atop the support shelf and that the shelf is completely missing on the rear jaw tower. When you hammer on something in the vise, that little shelf absorbs a lot of abuse. Sometimes you’ll see a crack start on the ends of the jaw towers, and other times sections of the support shelf break off completely like the picture above. Either way, it’s a sign the user was hammering the heck out of something in the vise.
The last thing to consider with hammering forces is that it can also damage the swivel base. Some brands have pretty substantial swivel bases that withstand a lot of abuse, but some are known to break pretty readily.
Below area some pictures of damage due to hammering forces, but before we get to those, take a second and think about a kind of vise intended to be used for holding objects to be hit with a hammer. A blacksmiths vise, or post vise, is exactly that kind of device. When you look at one, you can see how they’re built to survive being hit with a downward blow, and transfer the forces down to the ground through the leg, and to the bench/stump/etc through the bracket on the back. Another thing to note is that post vises are forged steel rather than cast ductile iron, or some sort of cast iron alloy. In other words, they’re made vertically instead of horizontally, and are made out different materials to withstand hammer forces. They say form follows function, and this is a very clear example of that concept. Okay, on to the pictures!
Dynamic support sheared off and how it should normally look:
Cracked jaw support:
Cracked swivel base (same vise from the cracked jaw support photo above):
The #4 thing you can do to break your vise is to actually use the “anvil” that many vises have as an actual anvil. There’s a joke in the vise community that vise manufacturers put “anvils” on their vises so they can sell more vises after people break them while using the “anvil.”
Why am I using quotations around the word anvil? Because a flat section of metal doesn’t necessarily make something an anvil. If you look at that part of most vises it’s made out of metal well under an inch thick. Even if it were an inch thick, how does that compare to an actual anvil? A small blacksmith’s anvil might weigh 5o pounds, have a top plate that’s 3/8ths of an inch of tool steel and then maybe another 10 inches of cast steel, cast iron, wrought iron, or something else similar to support the top plate. Also, the anvil on a vise is made out of the same material as the rest of the body of the vise. Nobody who knows anything about the topic would ever suggest ductile iron or one of the similar cast iron alloys would made an acceptable anvil. In fact, it doesn’t take much looking to know they’re right because of all the dents you’ll find on the anvil of most vises where a real anvil wouldn’t have a mark. If you’re using the anvil for soft metal like copper or brass, you’re probably okay, but once you get to harder metals, bigger hammers, and harder swings you aren’t doing your vise any favors and at some point, it’s going to break.
Here’s an example of how using the anvil can go wrong. To be fair, I’m not sure this vise has a machined anvil area, but many vises with this shape show damage in this area from hammering, even if the manufacturer never machined the space flat.
The #5 thing you can do to break your vise is hammer on the slide, and in this case we’re talking about a vise with a rectangular, exposed slide. I can only assume that people use the back of the slide to hammer on things because their vise doesn’t have an “anvil” and there are a lot of vises out there with cracked slides because of the practice. It’s only a guess, but I sometimes think maybe vise manufacturers put an “anvil” area on their vises to keep people from beating on the slide. It’s still a poor choice, but it’s better than beating on the slide.
When you look at the slide of a conventional vise from the side it appears to be a pretty substantial piece of metal, but flip it over and look at just how thin the metal is on the top and sides of the slide. The slide is really just an upside down U-shaped channel for the screw so it’s nowhere near as massive and strong as it may look. Some brands of vises are more known for cracked slides than others, but every one I’ve seen that was cracked had impact marks all over it. It’s a safe bet that the vast majority of them wouldn’t have cracked if they hadn’t been abused. Think of the slide as a precise guide more than as a structural member and treat it that accordingly.
There is a second problem that crops up when people use the back of the slide as an anvil on a repeated basis. Eventually the slide will show wear in the spots it makes contact with the static jaw, and sometimes the static jaw will show wear as well. What that means is the slide will be loose in the static jaw, and will pivot slightly as you tighten down on objects. While the vise will still work, it’s pretty annoying to have the dynamic jaw moving up and down in relation to the static jaw as you’re trying to use it.
Here is a classic cracked slide. You’ll note this already has a stop hole drilled at the end of the crack, but the damage is already done.
So there you have my top-five ways to break your vise. Avoid those five things, occasionally clean/lube it and your vise should outlast you (and me)!