Screwless vise screw stripped, why?

[WobblyHand]

The screw hangs on the edge just below the toothpick. If that edge is relieved the problem goes away. Maybe a chamfer, or something like that. Looks like there is enough room for a bigger screw as well.

Think I can machine this problem away!

 

[hman]

Couple of thoughts ...

1. The vise jaw is hardened, so it'll be difficult to machine. But you can relieve the edge with a small mounted stone in a Dremel or similar hand-held grinder.

2. You mentioned sometimes having difficulty getting the "ears" of the nut into the correct groove. That can be difficult with only the socket head cap screw and an Allen wrench to "aim" it. And it's one of the reasons I changed to the stud-and-nut setup I mentioned earlier.

 

[WobblyHand]

Couple of thoughts ...

1. The vise jaw is hardened, so it'll be difficult to machine. But you can relieve the edge with a small mounted stone in a Dremel or similar hand-held grinder.

2. You mentioned sometimes having difficulty getting the "ears" of the nut into the correct groove. That can be difficult with only the socket head cap screw and an Allen wrench to "aim" it. And it's one of the reasons I changed to the stud-and-nut setup I mentioned earlier.

Is the jaw edge machinable with a carbide end mill? Or is that just flushing money? It's no fun to break end mills.

How does having a stud and nut make "aiming" easier? Just a little bit longer handle to gauge the angle?

 

[hman]

With a stud, you have "direct" control of the direction in which the threaded fastener and the nut are pointed, and you can do it with your fingers (even better, if you use a coupler nut, you get that much more length to work with). With a socket head screw, you have to use a non-ball-ended Allen wrench to aim it. The ball end, though handy for fastening, is of no use in directing the screw.

Finally, having a stud sticking out lets you know when you're reaching the end of adjustability with the hex nut. With a socket screw, it's hard to tell when you're about to run the screw all the way out of the cross nut. And when you do that, you have to fish around to get the screw back into the nut.

 

[darkzero]

With a socket head screw, you have to use a non-ball-ended Allen wrench to aim it. The ball end, though handy for fastening, is of no use in directing the screw.

I personally hate ball ends for T-handles & hex bit sockets. They are handy though but now I only own them in traditional L keys.

I use these 2 Wiha T-handles specifically for my toolmaker's vises. I like them cause of the shorter length. I prefer to use T-handles for the toolmaker's vises cause they're quicker to use for me & are easy to access hanging on my work bench. I don't own the whole set, just these 2, & the shorter ones don't come in the sets anyway.

 

[Larry$]

I've got a 3" tool makers vice that I didn't like the way I had to deal with moving the nut along to the next catch point. I made a new nut out of scrap steel and it has worked fine for several years. In the photos of the "stripped" screws it looks like only the upper portion of the thread is damaged. If true, the nut threads are not being engaged deeply enough by the SHCS. Make a new nut and see if that cures the vice.

 

[nnam]

It looks like both nut and screw are ok, just that the nut didn't fall into the slot and as the result the screw didn't engage enough threads to stay or the nut just slide away from the non slot spot.
The thread doesn't look like it is bad.

Something else is the cause.

 

[WobblyHand]

Under some conditions the screw rests against the side of the hole that is in the jaw. So instead of the nut just simply tightening, the screw thread hangs up on the edge of the hole. The tool steel sort of becomes the nut. Of course it is fixed relative to the head of the screw, so the softer thread of the screw fails. The nut isn't even close to the area where the thread gets damaged. The damage is over 4 threads away from the nut - therefore it cannot be the nut. Although it is not obvious from my poorly focused previous picture, the edge of the hole (by the toothpick) is brightened due to contact with the screw. So somehow, I am going to take off that edge. That should reduce the problem.

Used a stone in a dremel like @hman said. Took off the razor sharp edge where the screw was contacting and rounded the edge of the hole in that area. Took 20 seconds at most. The edge is just below the pencil tip. If you blow up the picture you can see the rounding. Hope that's most of the problem. If not, I'll make a new nut and go up a size to 3/8-24. Yeah, some of these tools are kits. If that hole had been chamfered the screw would not have been damaged. Fortunately, that was an incredibly easy fix! Thanks @hman ! If this fails in the next 3 months, I'll come back and update the thread. Recently bought a DX4, so may not be using this vise as much. However, I used this as a primary vise for 5 months and have been pleased with it, save for the 3 screw failures.

 

[WobblyHand]

I personally hate ball ends for T-handles & hex bit sockets. They are handy though but now I only own them in traditional L keys.

I use these 2 Wiha T-handles specifically for my toolmaker's vises. I like them cause of the shorter length. I prefer to use T-handles for the toolmaker's vises cause they're quicker to use for me & are easy to access hanging on my work bench. I don't own the whole set, just these 2, & the shorter ones don't come in the sets anyway.

View attachment 373221

I love my Wiha tools. Have some torx screwdrivers for my carbide inserts, a small set of 8 screwdrivers (almost like jeweler's screwdrivers) for small stuff and a crazy combo screwdriver with built in storage for bits. That combo screwdriver has saved my bacon on the road, so it's earned its keep. Family photo: Or at least what I could find immediately when I was upstairs!

Love my Chapman tools as well, but that's a different and unrelated thread.

 

[extropic]

So the screw is not being stripped at all. Instead, a couple of threads are being damaged because of interference with the moveable jaw.

Does your vise include the hemispherical washer?

I think that kind of damage can be caused by the operator trying to get too much jaw movement without resetting the the nut into the next slot. That would be my guess here.

Alternatively, the clearance hole for the screw may need to be slotted a bit to allow more angle on the screw.
You could also just turn the threads off of the screw in the area of interference. Turn that area leaving a witness of the thread root. The screw will not be weakened.