Can't see how to adjust mikes
Have a 1", 2", 3", 4" mike set I bought used. The brand is Central Tool Cranston, RI. Need to adjust a thou or so but for the life of me, I cannot figure out how to adjust them. They are still in their original case and have, in the case, a small allen wrench (still in a sealed plastic bag). I see no allen screw anywhere, no notch for a spanner, nothing. If it matters, they are ratchet stop type mikes. When I totally unscrew the thimble and spindle, there is a friction nut on the split end of the female threads in the sleeve. This serves to control the ease with which the spindle screws in or out. That's it. Any thoughts would sure be appreciated. Jim
Just a couple of ideas that came to mind. Maybe there is a setscrew under the ratchet or somewhere in that area that will loosen to allow the barrel to be loosened from the spindle. Wherever the screw is that the wrench fits, the hole may be filled/covered with something. Careful inspection with good light and a high power magnifier might be needed to spot it. You can check the end carefully to see whether or not the index line is on is on a separate sleeve from the female threads. If so, it should be possible to change their relationship. If not, the adjustment must be between the spindle and the barrel markings. However, there are some micrometers with an adjustable anvil.
There is a small screw attaching the ratchet to the thimble. When I remove the small screw, off comes the knurled operating portion of the ratchet. With that gone, it exposes a male protrusion with one groove and then a platform above which is attached a spring that causes the ratchet action. This male protrusion is firmly attached to the thimble. I looked for a allen screw attachment in the screw hole and also did some light prying on the male protrusion and also pulled on the thimble but no allen screw and no movement at all. Thanks for the input. Do you have any further thoughts based on what I have said here? Thanks, Jim
No, I really have no more ideas except to wonder whether the protrusion the ratchet fits on might actually be a screw that fastens the barrel to the spindle. You never know how much force to use when trying to loosen something like that, it is a good feeling when it turns without falling off!! It also seems that surely the allen hex wrench fits something, somewhere. Good luck, it is better to live with the error than to ruin the mikes, especially since you can compensate for it.
Just a guess, but look on the end of the mike opposite the anvil. The anvil may be threaded and screw up or down to meet the spindle at zero.
Just to finish this up, I was able to contact the maker and they said that the thimble screws apart in its middle and exposes an allen scres the releases the thimble so it can be realigned for zero so I'm all zeroed in now. Thanks.
Have seen a small Allen in the (fiction ring)? Ring that control the tightness of the mik to find it screw the mik all the way out and look for a small ring.
Last edited by oldhat; 06-21-2012 at 09:44 AM.
Go to centraltool.com, they have a pdf file that shows the use, and adjustment of the mike. Good luck.
This is how to adjust an old Cranston Micrometer
You are having a problem because old Cranston Micrometers are different. Although it may not look there is a place to adjust it, there is, it's just well hidden. The factory web site does not mention older designs in their adjustment instructions.
First let me describe the thimble starting at the far end where the very small friction thimble is. That is the first place that is cross knurled then there are three more on the body of the thimble starting next to the friction thimble.
The first knurled section on main body of the thimble unscrews from the rest of the thimble body, exposing a large setscrew.
If you have studied the body of the thimble carefully you've already noticed that the lathe marks and angels that terminated all the other knurled sections on the main body are less abruptly ended and that is because that last section screws over the end of the main body.
I just bought mine a few days ago, it was not calibrated and I couldn't see how to get to the adjusters screw, or find instructions on the internet either, so I got out a jeweler's loop. As things turned out mine was also seized, so I had to take it out of the body, and sharply rap on it with a screwdriver to break loose years of corrosion.
I wouldn't call this a high quality mic, but the price was right and it's certainly good to at least a half a thousandth. An ex Mac Tool dealer was throwing it out because it had a little corrosion on it, so he couldn't sell it as a new tool.