# Lufkin Micrometer



## Gordon (Dec 28, 2015)

I have a Lufkin #621 0-1" micrometer. It reads .001 under size. I cannot find any way to adjust this micrometer. No holes for a spanner type wrench or cap to release the spindle. It does not appear to have any separate pieces in the body which would allow adjustment. It looks like one solid piece. I cannot believe that it was built in one piece with no means of calibration. It has four slots in the top of the threaded portion which may be for some type of spanner but the threaded barrel does not appear to be separate from the body. The micrometer is probably older than I am. Any ideas?


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## kvom (Dec 28, 2015)

Add .001 to each measurement.


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## Gordon (Dec 28, 2015)

that is what I have been doing but it seems like this should be correctable.


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## kquiggle (Dec 28, 2015)

Take a look at this link:

http://www.chaski.org/homemachinist/viewtopic.php?f=4&t=35074&start=0


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## Gordon (Dec 28, 2015)

Kevin:
I found similar instructions before. Unfortunately there is no removable cap. It does not look like it is adjustable. I just took the brute force approach and put the "C" in a vise and squeezed it together gently and now it reads correctly.


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## 10K Pete (Dec 28, 2015)

A picture(s) would really help. The four slots likely have a nut around them for adjusting the fit of the thread
and wouldn't help adjust the sleeve.

Pete


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## Gordon (Dec 28, 2015)

pictures of Lufkin


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## Swifty (Dec 29, 2015)

It doesn't show in the photo, but does it have a thimble ratchet on the end of the barrel ? I have an old 1" micrometer and to adjust it I have to loosen the screw holding the thimble on, then give it a shap rap on the end, this loosens the barrel on the shaft taper. It's then a matter of winding the shaft down to the anvil, setting the barrel to the zero mark and tightening up the thimble again.

Paul.


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## Blogwitch (Dec 29, 2015)

Compared to a standard mic, it just looks like they have relocated the adjustment to the end of the inner sleeve instead of just behind the 'C' casting.

Just make up a little tool that fits into those four holes and that will allow you to turn the inner sleeve in the casting. Maybe a couple of tight fitting drills in a couple of the holes and a bar between them should do it as well. Most manual mics have a hole just behind where it enters the casting and that is where the little 'C' spanner is used to turn the inner barrel and so realign your zero setting marks.

John


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## Gordon (Dec 29, 2015)

The mic does not have a rear ratchet. The spindle appears to be a press fit in the outer sleeve. I tried to turn the inner sleeve by putting a razor blade held in a vice grip and just broke the razor blade. It is four narrow slots, not four holes. I cannot see any crack between the inner sleeve and "C". Hard to believe that it is one piece but that is how it appears. I can find other similar mics on eBay but nothing else on the internet that would apply to adjusting this one. I have adjusted other mics using the wrench and they move much easier than this one which does not appear to move at all. I do have another Starrett 1" which I can use but this is the rough and tumble in the apron pocket everyday close enough mic. As I said I did use the brute force method and it now reads OK. I do not know how long it has been reading .001 off. It was OK at one point. This mic has led a rough life and is pretty beat up. It appears to have vice grip marks on the knurled part so maybe someone tried to use brute force before.


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## toolroom (Dec 29, 2015)

I have many older Lufkin inside, and outside as well as depth micrometers, as I collect them. If, and I say IF, there is no screw on the end of the thimble...Why not call a calibration institution close to home and ask how. 
I have brought older equipment into dimensional metrologists, and have had sweet returns,and really inexpensive too. It would be worth it in the long run to have it dealt with professionally before anything is forced or ...worse.
It's only worth a phone call!


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## bazmak (Dec 29, 2015)

can the anvil be taken out and shimmed ???


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## Gordon (Dec 30, 2015)

bazmak said:


> can the anvil be taken out and shimmed ???



Anvil cannot be removed. That would seem like a good way to adjust any mic but obviously that is not the way it is done so there must be a good reason.


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## Blogwitch (Dec 31, 2015)

I am positive that the inner sleeve is mounted just like any other mic, but with age it has got itself locked up rigid.
If it was in my hands, I would drill with a bit the same size as the inner sleeve through a block of hardwood, then cut that block in half and use it as a clamp around the inner sleeve in a vice. Then gradually try to start to turn the 'C' casting around the sleeve. Do NOT use any heat !!!

I used to have a large collection of very old mics, and once they had been calibrated by turning the inner sleeve, they all read as well and were as accurate as though they were new. 

Unfortunately, like a lot of old hands, I have gone from mechanical to digital, as it allows me to have one mic on the machine instead of two, but I still use manual mics for internal measurements.

John


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## gus (Dec 31, 2015)

Blogwitch said:


> I am positive that the inner sleeve is mounted just like any other mic, but with age it has got itself locked up rigid.
> If it was in my hands, I would drill with a bit the same size as the inner sleeve through a block of hardwood, then cut that block in half and use it as a clamp around the inner sleeve in a vice. Then gradually try to start to turn the 'C' casting around the sleeve. Do NOT use any heat !!!
> 
> I used to have a large collection of very old mics, and once they had been calibrated by turning the inner sleeve, they all read as well and were as accurate as though they were new.
> ...



Hi John,
Happy New Year.


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## Blogwitch (Dec 31, 2015)

And the same to you Gus, and all the other members on here.

John


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