"Jim Wilkins" wrote in message ...
I made a split bushing to hold short 3/8" Grade 8 bolts in a 5C collet like
in the "I love this tooling." example shown. Grooves near the ends hold O
rings that keep it together. Neither the hex head, shank nor threads run
true to each other so I have to clamp the bolt by the section I'm modifying.
OK, they are technically hex head cap screws when they go in a tapped hole
but 'bolt' is their common name.
The bushing's center hole is 0.370" diameter to match the shanks of the
bolts at the store, and before splitting I tapped it 3/8-16 to grab the
thread crests without damaging them, as rolled threads can be larger than
the shank. It lets me modify bolts to within as little as 1/2" from the
head, for instance to trim back the slightly-long shank so a nut bears on
the parts being clamped, or to cut a root-diameter pilot and pointed end on
the threads for simultaneous alignment of multiple 40 Lb parts with 0.370"
bolts in 0.375" holes. Those piloted bolts are longer and go at the outer
ends to stop the trolley after using them to align the center splice. Most
of the bolts joining my gantry track sections had to be modified to put
their shanks in the shear planes and clear the moving trolley.
My previous 5C bolt-holding fixtures are bushings with tapped holes, but
this version is more versatile and clamps tight on either shank or threads.
I split it with a hacksaw after scribing the end with a tool point aligned
with the 5C splits.