This is how I made a bolt to fit in an old vise with non-standard threads.
I picked up an Athol 624 ½ several weeks ago at an Estate sale. It was missing it’s swivel base. I managed to find a Starrett base that fit. Athol and Starrett are related, so the base off of a Starrett 624 ½ fit on the Athol 624 ½. There was one problem, the shoulder bolt that holds the base to the vise had different threads.
It turned out that my old Athol, guessing about 90 years old, needed a 7/8” main bolt with 12 Threads Per Inch (TPI). These days, standard threading for 7/8” bolts is either 9 (course) or 14 (fine) TPI. The Starrett base and parts, being newer, conformed to the now standard 7/8-9 thread.
So, do I make the vise fit the bolt or the bolt fit the vise? Having the vise drilled out and sleeve added with correct threads seemed expensive and would alter the original vise and threading. Likewise, having a new shoulder bolt fabricated also seemed expensive…and required finding a shop willing to do it. Looking for a easier (and less expensive) DIY solution, I thought I’d simply buy a 7/8-12 bolt and use a bushing. Simple, right? Nope. I searched extensively online for 7/8-12 bolts, but could not find any. But I was able to find several places selling the odd-ball 7/8-12 tap & dies. Apparently, 7/8-12 used to be a thing, because they still make the taps and dies.
My solution: I made my own 7/8-12 bolt. I bought a 7/8-12 tap and die off of eBay. Then I bought a standard grade 7/8-9 x 4 ½” bolt from the hardware store. The standard bolt had about 2 inches of unthreaded shank, which is what I actually needed. I cut the bolt off at just about the start of the threads, leaving only a couple threads and smooth shank. I didn’t have a die stock handle large enough to fit the 7/8-12 die, so I used a pipe wrench (which worked gloriously, lots of leverage). The die started easily in the remaining thread and I continued, using oil and going back and forth to clear chips, down the shank. Then, in order to replicate the shoulder on the shoulder bolt that I was supposed to be using, I fabricated a bushing from a piece of scrap pipe. I did have to grind down the head of the bolt a little for the vise to sit flat.
Now my Frankenstein Athol/Starrett vise is fully operational. (Athol 624 ½ static, Athol 614 ½ dynamic, Starrett swivel base.) Note: The only difference between the 614 ½ and the 624 ½ was the 614 ¼ had stationary base and the 624 ½ was swivel. So at some point, a previous owner of this vise replaced either the dynamic or static side.
