My 1st micrometer: do I need a ratchet?

[AluminumTube]

So I just bought my 1st micrometer on ebay (see pic) I chose a used Starret 216 with a mechanical digital display because I saw some old experienced guy on youtube saying that he had many and that this was his favorite.
However, I noticed that it doesn't have a ratchet. Is it better if I have one?

[utahwestie]

A-T

If the picture is the exact model of micrometer, then it has a "friction sleeve" which does the same thing as a ratchet.
Some machinist like these better for smaller parts, finding that more torque is used to
overcome the ratchet" than to stop it at the actual diameter

Utahwestie..

[WesHowe]

some old experienced guy on youtube

Undoubtedly Mr. Pete...

[SteveM]

I buy a lot of mics on ebay.

One thing you should do is close the jaws lightly and hold it up to a light or the sun. You should see no light coming thru from any angle.

If you see any, it will be on one side of the junction between the anvils. That would mean that the frame is "sprung" or bent.

You can also test if you have an accurate pin like a gauge pin or dowel pin - see what size it registers at four different positions (think 12, 3 6 and 9). It doesn't matter what size it reads, jut that it reads the same in all four positions. If the anvils aren't meeting square, you will see differences.

It's nice having one of those as it's impossible to make the mistake of which 25th you are on (especially with old eyes).

Steve

[choprboy]

I would second SteveM's suggestions to check for light and see if the anvils are square, then get a standard (or use a good known setup block or dowel) and check the readings at minimum and maximum extents. It will give you the opportunity to both gauge the accuracy and learn to get "the feel" of using the micrometer with known target measurements.

Personally, I like a ratchet style analog mic, or using a finger-slip technique on a fixed thumb wheel. Never liked my "digital" mic. But lots of people have different preferences of what works best for them, even preferences of one brand over another of the same method (I prefer my Mitutoyo ratchets, over my SPI fixed, over my Starrett ratchets for example).

[Rich_Carlstedt]

Friction Thimbles are far more consistent in operation and "feel" in my opinion.
Love my Starrett
Rich

[AluminumTube]

Thanks everyone, I will definitely try what you suggest when I receive it. I also bought this old starrett inside caliper. I guess I could have just bought a dial caliper instead of both of these tools. Maybe that was a better option. I've never used either, so I'm not knowledgeable enough to be sure.

[spro]

I think you got some good tools, Alum. One can be checked against the other by "feel" to develop that skill. The checks mentioned above are true but I can't imagine anyone springing the frame on that micrometer. The inside caliper is a "toolmakers" type which a more gentle inside caliper. I looked at the screw and it appears okay. This is a feely situation between the two and here's why; If you have a Known diameter you can adjust the inside caliper while it is straight and seeking the smallest or tightest diameter and remove it. Then measure against your micrometer (which you already checked for accuracy) and see it doesn't match. Then you narrow down the reasons it doesn't match. Was it a glide perfect fit or too tight-see where I'm going. Then measuring inside the mic, was it in the center of the faces? Was the mic too tight to feel the caliper? Between the known and unknown, one gets closer to the "feel"

[liveaboard]

I used to watch my Indian machinist friend use the system described so well by Spro; he made it look really easy.
A few years later, having obtained the same tools I tried it myself.
It's actually quite difficult to get an accurate result.
Practice, practice...

[wlw-19958]

Hi There,

Friction Thimbles are far more consistent in operation and "feel" in my opinion.
Love my Starrett
Rich

I agree. I find the inconsistencies in the ratchet between different
mics annoying. Also, the speed one twists the ratchet can affect
the reading too. Of course, after years of using mics, I tend to not
use the ratchet and just "feel" the mic when it closes. I like my 230
Starrett.

Good Luck!
-Blue Chips-
Webb

[earlgo]

Another way to get the best of a mic is to "feel" how much torque is required on the thimble to get the zero reading. (Assuming the anvils are clean.) Then you can approximate that "feel" when you take a measurement.
My Starrett #436 1 in and #436 2 in do not have ratchets or friction thimbles and I have never wished they did.
YMMV.

--earlgo

[wlw-19958]

Hi There,

I too have mics that are plain thimble mics (my B&S #1 and
my Starrett 436 1" - 2") My Starrett 436 is calibrated in 1/2
thousandths. I wish I could find some other 436's with this
feature.




Good Luck!
-Blue Chips-
Webb