Reed Small Tool Works inside micrometer stiff

I recently acquired this nice little set on ebay. The seller mentioned that is was stiff to turn. I didn't think much about that as many old micrometers can be stiff from gummed up oil. Well after I cleaned it up is is VERY stiff nearly too stiff to turn by hand. The female thread looks fine for the first 5 threads or so, then the thread looks a bit buggered up, for a thread or two, then its OK again. It threads on fine until it gets to the odd looking part. I tried to get a picture of the female thread but I couldn't get it to show up. It appears that the thread is an insert into the barrel. Also the presence of the hole for the wrench is a bit curious, I can't see what that does exactly.

I went looking and found a Reed catalog online:
Reed Micrometers : Catalog No. 9 : Reed Small Tool Works : Free Download, Borrow, and Streaming : Internet Archive

Note it says: "The micrometer is set in tension, so that in use the measurement setting will not be loosened before reading is ascertained"

That gives a clue and maybe explains the appearance of the threads, maybe there are two collars that are slightly out of sync?

Anyone have one of these? How stiff is it to turn? Any ideas on how I can loosen it up?

Thanks!



sorry pics are upside down despite that I turned them right side up on my computer!

Apparently Reed did not include tension adjustment in their design. I am guessing the nut is split and the ends deformed inward to apply tension to the screw. You might try putting a brass or aluminum rod into the nut and try to pull the nut open just a bit. I have several inside mikes. All have a tension adjustment. The nut has a tapered thread on the OD, the nut is split at the open end and a sleeve with a tapered internal thread gives the adjustment.