Frozen micrometer

[TomG]

It would be very unusual for the threads of a micrometer to seize due to rust, especially since none is showing on the outside. I would suspect that all it is is dried grease on the spindle where it goes through the frame. Try warming it with a heat gun to speed up the penetrating oil and it should loosen right up.

Tom

[JScott]

Tom, good tip and I have contemplated doing a heating and cooling expansion/contraction cycle with a hair dryer and upside down canned air. I was hoping it was just congealed lube in the threads but this thing is locked down tighter than Dick's hat band. I mean it doesn't wiggle or budge. I tried turning the barrel using the little adjustment spanner and felt no give in either direction. I have done a little reading and research and apparently the thimble can be pulled off the barrel. It might require some tapping though. The program now is Kroil until the weekend and then the wrestling begins!

[awemawson]

Put it in a pan of the lightest grade of sewing machine or other oil you can find - even 'Plus Gas', and slowly raise the temperature to 100 degrees C and hold it there for an hour. The heat will allow the oil to penetrate

Obviously take all steps to avoid the oil bursting into flames !

[JScott]

(04-23-2014, 02:44 PM)awemawson Wrote: Obviously take all steps to avoid the oil bursting into flames !

Caution noted! I think this will be the method I try after electrolysis!

[awemawson]

Might be too late AFTER electrolysis, in my experience it doesn't penetrate far. Mainly 'line of sight'

[awemawson]

On a much larger scale I once had the four platen lifting screws of a 60 ton hydraulic press rusted solidly into the bronze nuts that they screwed on. Nuts each had 4" of embedded thread. Machine had been in an intense fire, then dowsed with fire hoses, then left in a burnt out building for six years - they were solid.

I did much research on rust and its removal from threads! The best solution I found, and it eventually worked, was Citric Acid. I seem to remember that the volume of rust is something like ten times the volume of the original steel. Citric acid acts on the rust to form iron citrate, which is water soluble. The result is that over time the citrate migrates out into the body of the water allowing more acid in. This is unlike many other acids used for de-rusting which form insoluble compounds that although smaller in volume than the rust, are still larger than the original steel.

Now at this stage I'm NOT advocating citric acid for your micrometer, but I'd certainly use it in preference to electrolysis as you cannot be absolutely sure what metals you are dealing with.

.. the 60 ton press . . yes now working fine :)

[stevec]

The reason electrolysis wouldn't work is because the action takes place between the anode and the cathode the mic becomes ONE piece, the anode (or is it the cathode, I forget) so the parts of it's makeup are all one "ode" (anode or cathode).

[awemawson]

Well no, the micrometer would be the negative cathode electrode, and a sacrificial anode would be put in the solution. However I still wouldn't use this method in this case

[stevec]

(04-23-2014, 04:17 PM)awemawson Wrote: Well no,

What do you mean "Well no"? and thanks for pointing out which is which (I was too lazy to look it up).
What I meant to say was the electrolysis happens between the anode and the cathode. The entire micrometer's surface would be the cathode, it's internal parts wouldn't be acted upon. It's like shining a light on a box of cookies, only the surface of the box receives the light not the cookies therein.

And, I agree, it would not be a recommended approach in this case.

[Mayhem]

I think the "well no" was aimed at the incorrect choice of 'ode'.

Remember, when faced with a 50-50 choice, you will choose the wrong one 80% of the time...