What's it or how to use it

So far as the threads binding on the parallel clamps, the clamp bodies were obviously tapped, and I suspect that the screws were threaded with a die that did not cut an accurate pitch, not matching the pitch cut by the tap, if the thread is cut for a close fit in the tapped hole, the pitch inconsistency causes the binding. Pitch irregularities in dies are not uncommon. Another possible cause could be that the thread was cut to a pitch different than the tap, or vice versa. Try a good sharp tap, matching the thread of the screws in the holes and see if any significant material is removed.
The second item is obviously the staff for a surface gage, having the ball end and scriber on the opposite end, what the other part is, I do not know for sure, have never seen this part in old catalogs, but it may have been to mount a dial indicator on the surface gage, it does not look to be home made.
 
Funny thing, I still figure out the first phots (clamps). Yes, it obvious what they are and how they are used.

The weird thing is that the threaded rods almost but don't quite match the threads in the jaws. I can get 3-4 full thread rotations and then they just jam up. Same results trying all hole/rod combinations and either side.

The threads match but not quite.

It seems that both are hand/custom made - so maybe the thread tuning job on the rods was messed up?
If so why keep them and not make another set / fix it?

Like you said, maybe I'll find out when I talk to dad in the afterlife!

(John York - our posts collided. I was planning on trying to re-tap or clean up the thread on the clamps. The question to dad is still - why keep them and not fix them?)
 
Are the clamps Starrett? Starrett is known to have odd ball thread pitches that are not common. I guess just another excuse for proprietary exclusivity.

Mine are not Starretts but the jaws have to be parallel or close, or they screws bind. I don't use them everyday but they have come in handy enough that I'd not be without them.
 
C-Bag said:
Are the clamps Starrett? Starrett is known to have odd ball thread pitches that are not common. I guess just another excuse for proprietary exclusivity.
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No markings at all on the jaws. These are most likely "made in the shop"

I re-tapped the threaded holes and then used a die to clean up the jacks. Lots of cutting running the die on the jacks. Working great after that.

My best guess now is that these may have been a "lab" when my father-in-law learned to be a machinist. The jack threads were probably cut on a lathe, by a novice and ended up too tight. I can't come up with a better story.

Why he hung onto them and never made them workable is beyond me.

His education was sufficient enough to be employed at the Portsmouth NH navel shipyard machine shop for years. Based on all of the other kit I've inherited, he knew what he was doing.
 
Maybe the clamps in #1 were hardened and the threads shrunk or distorted. Lightly try the hardness with a file and see if They are hard.
 
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