Kurt Vise Question

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RWL

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I bought a used 6" Kurt milling vise. I'm not entirely sure what the previous owner did to it, so I don't know if the screw is the right screw for this vise or one that he made for it. When you close your vise fully without anything in the jaws, do the threads protrude from the nut by about an inch or are they entirely contained in the nut? Photo of mine below.02 Threads sticking out of block (Large).JPG

I've repainted the vise. It looks much nicer than when I bought it. The reason I ask is that the seller had a photo of a nice Kurt vise covered in chips in his machining center and hauled out this one when I came to look at it. He told me that when he bought it that the screw was rust frozen in the nut and he worked hard to get it out. When I was at the shop, I didn't fully open the vise, just checked that when it clamped down it was locking. At home I discovered that the jaws wouldn't open fully due to rusty threads in the nut. I solved that with about 2 hours of electrolytic derusting followed by copious brushing and rinsing to get any loose iron oxide (surrogate grinding compound) out of the nut. I noticed that the screw had nearly sharp threads rather than having the flat on top that I associate with a worm thread. Those things made me wonder whether the previous owner made a new screw for the vise after he got out the frozen screw.
 
I have 1 inch thick soft jaws in mine, the threads just show at the end of the nut when closed. I think I remember them as being sharp threads.

When I bought my pair, both were frozen. An hour with an impact wrench, and about a quart of PB Blaster got them freed up. Once I got them cleaned up and painted, they are a nice matched set of vices.
 
looks normal to me, also
 
My jaws are hardened and just under 3/4" thick, so a total of 1.5" thick compared to the 2" thick soft jaws. That would explain 1/2" of the screw sticking out of the nut. I re-measured the amount of screw sticking out, this time with a depth gage rather than a ruler and it's 7/8". Sounds like that's the way they're supposed to be.

Noting the comment above about the impact hammer, I'd like to recommend the electrolytic rust removal method to anybody else who reads this in the future. I too tried to get the screw to pass the region of obstruction in my nut with Kroil and forcefully turning the nut. It advanced a little, but was clearly a losing battle with the potential to do damage to the nut or screw. After 2 hours in the electrolytic tank, the screw passed through the rusted area easily. Since I could take the screw out, when I did the electrolytic process, I put a 1/2" bar in the nut's screw hole as the anode and separated it from the nut by using some sections of plastic tubing on it to prevent it from shorting out. The action was concentrated inside the nut that way. I believe it would work on a completely frozen screw and nut, but would probably take longer.
 
Those threads look rather rough. My Kurt does have V threads,too. I just question the apparent rough finish shown.
 
I think they look worse magnified by the camera than they do without magnification. I'm sure they suffered some from the rust, but they don't really look bad when holding the screw in your hand.
 
I realize that,of course. I'll have to go out and have a look at mine later. Will report back unless my old head forgets to!
 
+ 1 looks OK to me, just like mine.

Tom
 
Depending on which model of vise, some have threads showing, some do not.

tmp_12857-20150408_101103149112747.jpg
 
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