Adjusting a Lufkin 680A Inside Micrometer

I recently bought a very used but complete Lufkin 680A Inside Micrometer
set (for bores from 1.5" to 8" diameter, resolution 0.001"). I don't
know how old it is, but the holder has a patent number on it (1,615,488,
issued 25 Jan 1927), so it's probably from the 1930s. It looks it.
Anyway, I've been cleaning and adjusting it. Everything was a few
thousandths short, largely due to wear at the contact tips (which do not
appear to be hardened). The extension rods are easily adjusted with a
wrench, but how to adjust the micrometer core (screw and scale) is less
clear.
I tried to find a patent number for the micrometer itself, but didn't
succeed. That isn't to say that none exists.
Does anybody know anything about this micrometer?
Joe Gwinn
Reply to
Joseph Gwinn
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Normally on a micrometer the scale is held in a collet, and you can loosen the collet and simply twist the scale. Some come with a little wrench for this purpose. I very strongly doubt that there is several thousandths of an inch of wear on every rod - it's much more likely that the scale is simply off by a few thousandths and that all the rods are well within .001" of correct.
GWE
Reply to
Grant Erwin
if no one gives you the definitive answer in a few days, contact me directly and I'll scan the adjustment instructions that came with my Lufkin set (I have aprox the same set, I think) and email them to you - you can get my email off my web page,
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Reply to
William Noble
Yes. I have a number of micrometers with such collets, and have the little spanner wrenches that come with the micrometers, but there is no obvious way or place to use such a wrench on this unit.
The collet nut that tightens the female body thread upon the male spindle thread is knurled.
The barrel with the index mark (opposite the rotating barrel with the scale) is perfectly smooth, and 0.400" in diameter. On other mikes I have, there is a little hole for a spanner.
The other possibility is to rotate the scale with respect to the spindle, but I don't see how to do this, and am afraid to force it.
I measured each rod individually. All were off a bit, as were the end cones used when no rod is used.
All the handling surfaces were that iron gray matte finish that comes from years of use by grimy hands. There was no rust whatsoever.
I suspect that as the original machinist (and his son?) aged, their waistlines and bores both increased. And they got their money's worth out of this micrometer set.
Joe Gwinn
Reply to
Joseph Gwinn
Actually, I'd like to see them in any case, and would suggest that a high-resolution scan of these instructions would make a fine addition to the dropbox collection.
Thanks,
Joe Gwinn
Reply to
Joseph Gwinn
ok, posted to drop box as lufkin-instructions (txt and jpg)
Reply to
William Noble
Got it. The only difference between 680A and 680B is that the 680B set has one additional rod, a six-incher. The longest rod in the 680A set is four inches.
Patent number 1,424,383 was the key, reinforcing the instructions, showing how the sleeves are built. I could see the splits when I looked into the annular cavity between spindle and sleeve.
Anyway, the 680A is now re-calibrated. This required polishing 0.0004" off the less-worn cap, making the caps equal, adjusting the micrometer core to read correctly with the two worn caps, and adjusting all the rods to match.
With any luck, this 680A will end up with 100 years of service.
Thanks,
Joe Gwinn
Reply to
Joseph Gwinn
Can someone email me the instructions to adjust the Mic head?
Reply to
andres padilla
William, Can you send me a copy of those instructions also. I have not been able to find a copy on the web yet. Thank you. Joe Rich
Reply to
Joe Rich
Morning all, I was trying to find the instructions for adjusting the Lufkin 608A mics and haven't been successful. Can someone help me out please? Chuck
Reply to
CJCastiglione
Morning all, I was trying to find the instructions for adjusting the Lufkin 608A mics and haven't been successful. Can someone help me out please? Chuck
Reply to
CJCastiglione
Good Morning Gunner Any chance you still have the details explaining how to do the adjustment? I've figured out how the micrometer head works but there must be a better way of adjusting than tapping the inner threaded piece back and forth until the mic reads correctly? Thanks!
cjcastiglione AT verizon.net
Reply to
cjcastiglione1
Is there any chance I could get instructions how to adjust the Lufkin 680 inside tube mic.. I googled it and found you, Thanks
Reply to
Randy
Is there any chance I could get instructions how to adjust the Lufkin 680 inside tube mic.. I googled it and found you, Thanks
Reply to
Randy
Hi Randy Adjusting the extensions is accomplished by rotating the end piece in or out. The micrometer head is more of a PITA. Remove both of the tiny end caps and using a .0001" indicator, make both caps identical thickness. I used some 400 grit emery cloth on a flat block. Install the caps on the micrometer head and set it to 1.000" on the barrel. Use a set of good mics and see which way they're off.. Now dis-assemble the head completely except for the insert that is light press fit into the barrel. You need to move the insert in or out to change the reading. I used a bench block and a gage pin that fit the barrel to bump the insert. Repeat the above steps until you get it right. It's a PITA. Once you get the head adjusted correctly then do the extensions. Let me know how you make out.
Reply to
CJCastiglione
Hi Randy Adjusting the extensions is accomplished by rotating the end piece in or out. The micrometer head is more of a PITA. Remove both of the tiny end caps and using a .0001" indicator, make both caps identical thickness. I used some 400 grit emery cloth on a flat block. Install the caps on the micrometer head and set it to 1.000" on the barrel. Use a set of good mics and see which way they're off.. Now dis-assemble the head completely except for the insert that is light press fit into the barrel. You need to move the insert in or out to change the reading. I used a bench block and a gage pin that fit the barrel to bump the insert. Repeat the above steps until you get it right. It's a PITA. Once you get the head adjusted correctly then do the extensions. Let me know how you make out.
Reply to
CJCastiglione
Hi CJ, you were right about calibrating the mic head its self being a PITA !!!, But I finally did get it ... I knew how to adjust the individual rods but the Mic itself was a mystery. Its unlike a Starrett that you can easily adjust. I really do appreciate the Info... Thank you my Friend
Reply to
Randy
Hi CJ, you were right about calibrating the mic head its self being a PITA !!!, But I finally did get it ... I knew how to adjust the individual rods but the Mic itself was a mystery. Its unlike a Starrett that you can easily adjust. I really do appreciate the Info... Thank you my Friend
Reply to
Randy
Does anyone have a copy of the instructions for adjusting the Lufkin 680a?
Reply to
Dudy

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