Problem With Starrett 733 2" to 3" Electronic Micrometer

Rick H

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Hi All: I haven't been on this forum lately because I have been busy with a bunch of stuff. I recently bought a slightly used Starrett No.733 2" to 3" Electronic Micrometer. The price I paid was more than reasonable and I snapped it up from the guy that had it. Unfortunately, I paid more attention to how the electronic display worked than the "mechanical" readings on the sleeve and thimble. It came with a 2.0" gage block which is spot on per my other measuring tools, but when I install the gage block the thimble shows a reading that's .015" undersize. I have verified this with some of my other gage blocks. So my question to the group is this, does anyone know of a way to correct this problem without sending the micrometer back to Starrett? I don't think that this could be corrected by simply turning the sleeve as .015" is a lot of turning on the sleeve. Thanks for any help in this matter.

Rick H.
 
Unscrew the flat head screw on the right side a turn or two. then hit the head with a hammer while holding the thimble next to the numbers. I will post you some photos tomorrow.
 
Thank you sir, I appreciate it. I contacted Starrett on this and they want about $183.00 to fix this issue. If I pay that much I wipe out all my savings on this mic. I must say I am intrigued by how this is accomplished.
Rick H.
 
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Just a pic so you can see the problem. If you look at the thimble you will see that it is turned in almost .015" past the zero mark on the sleeve. The gage block is in place and it is quite accurate. The read out can be doctored to give almost any reading and I have it set for .00000" with the gage block in place.
Rick H.Starret 2-3 Mic.jpg
 
There's probably a workable solution, but it won't be pretty. All the good quality micrometers I've seen have a small hole in the "fixed" sleeve (not really sure of nomenclature - the part the thimble reads against). They also come with a small hook spanner. You use it to rotate the sleeve to set the correct zero. I have a couple extras, so if you need one, PM me and I can mail it to you (no charge).

Unfortunately, in your case, that would place the "zero" mark of the fixed sleeve way around the back of the mike, making it kinda inconvenient to read. My best guess is that the micrometer frame got sprung at some point in its history, and the seller just wanted to get rid of it ... thus, the low price.

Another thought ... wonder if it's possible to adjust the anvil inward???? No idea how to do this, but maybe somebody on the forum will know if I'm just blowing smoke.
 
Sorry for delay, I only got the time now that I'm off work. As said above now in more detail. Unscrew the micrometer to about half an inch, take a small flat head screw driver to unscrew the back screw a turn or two. Hold the knurled thimble next to the numbers, not the spinning friction torque limiting barrel. Hit the head of the screw with a hammer to bread the hold on the tapper. Once apart you will see that the end of the spindle has a small tapper like a moorse or Jacobs tapper. rotate the thimble to the desired position then lock the tapper in with a gental strike of a hammer then tighten the screw on the end.
 

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Alexander you ARE the MAN!! I did almost exactly what you said and in three attempts had an absolutely perfect "zero" on the thimble and sleeve. And for this Starrett wanted $183.00 plus shipping. I have verified this zero reading on three different gage blocks and all read the same. I owe you my friend. Thank you very much for the help!!! Oh and I didn't have to strike it with a hammer to get it apart, I just pulled hard on the thimble and it came off. I should add that when I received the mic the spindle lock was really screwed down super tight. I wonder if that didn't lead to the thimble turning/slipping on the spindle? And your pictures were a big help in showing me what to do.....:grin: Can't thank you enough, you saved me from a severe tongue lashing from me wife!

Rick H.
 
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