Micrometer Reading Help

seal killer · Post by **seal killer** » Tue Oct 13, 2009 7:28 am

Harold--

A few posts above, Glenn posted a site that explained the anvil cleaning procedure. I am going to follow it. Plus, I believe I have the "feel" you mentioned, or at least something approaching it.

--Bill

seal killer · Post by **seal killer** » Tue Oct 13, 2009 7:33 am

Jose--

You are right on the money, as usual. Below is a picture of the screw you mentioned. First, I will try my spanner wrenches. If that does not work, I will attempt to adjust--very carefully--by loosening the screw and tapping lightly on the screw hoping that will be sufficient!

--Bill

Falcon67 · Post by **Falcon67** » Tue Oct 13, 2009 10:41 am

Also note that the knurled knob do-hicky on the end is probably a friction-spin set up, which allows you to run the mic down on a part with the same torque each time to get equal readings.

Gunbuilder · Post by **Gunbuilder** » Tue Oct 13, 2009 10:49 am

micrometer also known on eBay as a C-clamp!

Paul

seal killer · Post by **seal killer** » Tue Oct 13, 2009 11:16 am

Jose and Harold and All--

I took a wrench from one of my other mics and it fits perfectly. However, the thimble is really stuck and short of using a vice and a pair of channel locks, I cannot break it loose.

So, I liberally doused the pathways to the internals with penetrating oil and am going to let it sit for a bit.

There is a picture of the ratchet screw loosened way up (I've had it off and cleaned the mechanism, being careful not to lose the pin and spring that makes the ratchet work). Plus, there is a picture of the wrench.

I have been trying to turn the wrench in the counter-clockwise direction (unscrewing for a RH thread), but does the direction make a difference if it is merely a press fit?

I have not tried tapping on the top of the screw, yet. Should this be done with the ratchet thimble in place, as is shown in the picture? It looks like any movement will force the ratchet "gear" (pawl?) to move on the shaft. If so, what does this mean for re-assembly? Once the "gear" has moved on the shaft, will the thimble become loose? Is the idea to loosen the thimble, slide it toward the end of the shaft, then tighten the screw until the "0" coincides with the zero mark when the anvil surfaces contact?

Thanks!

--Bill

Inspector · Post by **Inspector** » Tue Oct 13, 2009 12:25 pm

Don't hit that screw. It only holds that type of ratchet mechanism on. The little hole on the barrel is most likely holding that thimble to the 40 tpi shaft. Perhaps a modification by a previous user or unique to that maker.

The knurled thimble is usually attached to the shaft by a taper and a rap with the wood handle of a small hammer to the side should make it break free. Then you slip it back on to align the lines. This is usually done as a coarse adjustment to bring it back to the side of the micrometer.

Fine adjustments are done by rotating the sleeve with the little spanner you have. The pressed on sleeve will move in both directions to get the zero and may take some force to move it if it has been a while.

Pete

Jose Rivera · Post by **Jose Rivera** » Tue Oct 13, 2009 3:27 pm

Bill ... that hole on the thimble troughs a wrench on what I can help you with.

Never seeing one like that.

Sorry !!

seal killer · Post by **seal killer** » Tue Oct 13, 2009 3:43 pm

Pete and Jose--

Pete, I'm glad I let it "cogitate" in penetrating oil for a few hours instead of working on it! Thanks for the help!

Jose, it is a Lufkin Rule No. 1641. My ignorant guess is that it was very popular. Picture below.

--Bill

seal killer · Post by **seal killer** » Tue Oct 13, 2009 6:43 pm

Jose and Pete and All--

Got it! I had to put the micrometer wrapped in a towel and protected by soft jaws, in a bench vise after taping on the circumference of the cylinder with a small wooden hammer handle. By this time, it had already soaked in penetrating oil for about four hours.

Still, it was not easy to loosen the thimble. The oil inside had turned very sticky, but the wrench finally turned. I took the ratchet thimble off and then removed the adjustment thimble, cleaning both very thoroughly in the process.

I stuck it back together, fiddling with it a bit to see how best to adjust it. The results with the same 0.250" plus plug gage are shown below. (Refer to the same picture above to see the before and after difference.)

Tell me if you think it is right on the money, close, or close enough. (Or if I need to do more.)

Thanks!

--Bill

mechanicalmagic · Post by **mechanicalmagic** » Tue Oct 13, 2009 7:26 pm

seal killer wrote:The results with the same 0.250" plus plug gage ......

Tell me if you think it is right on the money, close, or close enough.

Bill,
I'm a bit bothered by your calling the gage pin a 0.250" plus. Do you know it's exact size?

If it's 50 millionths over, then I'd say you are right on the money.

Dave J.

Post by **GlennW** » Tue Oct 13, 2009 8:13 pm

Looks like you forgot the .0002"!

seal killer · Post by **seal killer** » Tue Oct 13, 2009 8:58 pm

Dave and Glenn--

Dave, in my ignorance I thought ALL plug gages were 0.0002" . . . either plus or minus. Sorry about that.

I have 0.061" through 0.250" sets in both plus and minus 0.0002".

Glenn, thanks for making my mistake clear to me. Do plug gages come in MANY different +/- sizes?

--Bill
ps Dave, the gages are not 50 millionths over. Do I need to figure out a way to adjust the mic more?