Adjusting a Millers Falls micrometer

I have an old Millers Falls micrometer that somehow is out of calibration
by about a half a thou. How do you adjust these? I've adjusted other
types where you grab the sleeve (Starrett) or the end of the thimble
(Polish import) with a little spanner wrench, but I can't find any such
mechanism on this Millers Falls item. It's been trustworthy for many
decades (from former owners and lately me), made in the USA, and
wonderfully dinged up and cosmetically worn, so I have an attachment to it.
Reply to
Richard J Kinch
Loading thread data ...
"Millers Falls" -- I think that my first micrometer was by them, and bought in the shop attached to a commuter train line's station.
IIRC -- that one had only one way to adjust it.
1) There is a small hex just where the small knurled spinner mates with the spindle. Find an ignition wrench which fits and loosen this.
2) Pull the thimble away from the body of the micrometer. (There is a steep taper where they join.
3) Turn the spindle with light finger pressure on the taper until the micrometer closes. Lock the spindle.
4) Slip the thimble back onto the spindle and align the zero with the index line.
5) Holding by the thimble, re-tighten the spinner to secure the thimble to the spindle.
6) Unlock the spindle, and try closing it and make sure that it comes to zero with the proper feel. (You may need to re-adjust this a couple of times to get it right.
Note -- this is assuming that the problem is not dirt or grit in between the spindle face and the anvil face. So -- before you do any of the above, open it enough to slide a piece of clean white paper in between, and then close lightly on the paper while you draw it out. This should remove any grit.
Now if the spindle closes to just below zero, then you may have badly worn spindle faces. Mine did not have carbide faces, and yours may not either.
If the spindle and anvil faces are worn, there is a good chance that they are worn to form a taper which is wider in one rotational position of the thimble than in another 180 degrees different. The way to test for this is to close it gently on a quartz flat and observe under monochromatic light -- typically a selected line from a sodium vapor light. If it is tapered, you will see bars from one face to the other. And you really need two of these flats -- one about a quarter-turn 0.006" thicker than the other, so the spindle will be at 90 degrees to the first setting. If you have this problem, the way to fix it involves precisions lapping -- which will probably cost you more than a replacement micrometer of equal quality -- unless you figure out how to do it yourself.
The taper really will matter only if you have one with the tenths vernier on the barrel.
You can probably get it close enough for most of your work by following my suggestions above -- assuming that it is built like mine. I wish that I knew where it is now. :-)
Enjoy, DoN.
Reply to
DoN. Nichols
On Tue, 22 Apr 2008 22:43:12 -0500, with neither quill nor qualm, Richard J Kinch quickly quoth:
What, you don't have a vise?
-- Happiness in marriage is entirely a matter of chance. If the dispositions of the parties are ever so well known to each other or ever so similar beforehand, it does not advance their felicity in the least. They always continue to grow sufficiently unlike afterwards to have their share of vexation; and it is better to know as little as possible of the defects of the person with whom you are to pass your life. -- Jane Austen, Pride and Prejudice, 1811
Reply to
Larry Jaques
Exactly. This is what I couldn't figure out. These pieces didn't want to separate without colleting the spindle and applying some taps from a mallet. Thank you.
Reply to
Richard J Kinch
I confess to many vices.
Reply to
Richard J Kinch
Or vise grips? Gerry :-)} London, Canada
Reply to
Gerald Miller
Glad that it worked for you. IIRC, I simply applied a light tap to the end of the spinner after loosening it a turn. But then, mine was purchased new. :-)
Enjoy, DoN.
Reply to
DoN. Nichols

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.