The Unbelievable True Story Of The Amazing Vise Jaw Caps*

*(title inspired by YouTube - I should add "Shocking!")

 I use vise jaw caps to keep from indenting my workpieces with the diamond pattern in the hardened steel factory jaws.  Clearly, I should probably make a "regular" set of vise jaws which are soft low carbon steel.

 But see, sometimes I need something softer than that because the work is really soft or highly polished, is made of plutonium, or what-have-you. 😇

 The time-tested solution for this is to have a variety of soft jaws for not only bench vises but even for lathe chucks, if your chuck supports removable jaws. (mine does)

I have on hand, courtesy of Hoarder Fright Casinos, a pair of soft jaws in very soft urethane, and a pair in some variety of nearly-dead-soft-but-not-quite-pure aluminum.  Both were super-duper-cheap.  Both are equipped with ceramic magnets to hold them against the vise jaws. All the magnets are broken.  I half-assed a repair on the aluminum caps with JB Weld, but ceramic magnets are brittle...

 I kept telling myself I'd make some from brass, when I had the right stock...

 Now, years ago, I salvaged an L-shaped strip of what I assumed was brass, from the side of an unsalvageable rusted and worn chinese magnetic vise, where it was used as a non-magnetic "stop" for the work.
And then I forgot about it for years, even when I was thinking about jaw covers for the bench vise, because I have been senile since I was fifteen years old...

 I unforgot it this morning and dug it out.  Not only is the cross-section shape exactly the desired shape for vise jaw caps, saving me a boat-load of machining time, but the cross-sectional dimensions are perfect for my vise too! 

 Very well, let's make some vise jaw caps.  Uh, gee whiz, this stuff sure cuts slowly and feels "slippery" with a brand new, sharp hacksaw blade.  Whatever it is, it is not "brass"; it's either phosphor or Al-Si bronze, which is very nice (but hard) stuff indeed. (I mean 'hard' relative to cupric alloys, not 'hard' like tempered steel - completely different scales!)

 Well now I have a quandary; the important property of the jaws is that they be soft - or at least, softer than steel.  And while this stuff is much harder than any variety of brass, it still meets that qualification.  But it will put dents in copper(s) and brasses.

 Fine then, I am resolved to make (later, not soon) a pair of thin copper soft jaws which simple wrap around the vise jaws.  And so I will also make these...

 I want these to be held in place with magnets like most bench vise soft jaws.  Ideally, I'd mill out a couple of pockets in each cap, stick some thin rare earth (NIB) magnet disks in (top surface below surface of cap) with a dab of JB Weld (magnetic!) under and over the magnet disk.  Then, when cured, mill off the top coat of the JB weld so it's flush with the surrounding bronze, and the magnet is not exposed.  That should keep the magnet from breaking, in theory.  I'm not even sure rare earth (NIB) magnet disks are available thin enough, but I'm about to find out. They absolutely do.  0.5mm!

 I considered flexible magnetic tape, but it's not very strong, and it wears and breaks and gouges easily.

 So I nearly finished one jaw this morning before I'd finished my first cup of coffee.  All I had to do was cut it and square up the ends on the mill, and break the edges and corners.  This material creates chips which are half powder, and half tiny chip, indicative of a hardish material.  It machines fine with HSS and brushed-on Tap Magic, and a surprisingly slow SFM; like 100-200.  So I can't tell which kind of high-strength bronze it is, but it makes sense in the original application that someone wanted something that wasn't magnetic, but also wouldn't wear much, at all, ever, because it was for a surface grinder, where tenths (1/10,000th) matter.  It's not as soft as brass, but it sure won't get dinged or bent easily!

 The two circles show the approximate location and size of the bored / milled pockets for the magnets.  The lines are where the pockets for the jaw mounting screws end, so I make sure to miss them.

 Today's efforts were brought to an abrupt close by severe unexpected back pain, so not much more work likely to be done out there today unless that improves.  Ow.