Small Range Inside Micrometer

[rake60]

Here's an inside mic that fits this hobby very well!

It's range is .200" to 1.200"
It's limitation is that it only measures the hole diameter to a depth of about .200"
For the price at ENCO it's pretty tough to imagine being without one.

Rick

 

[mklotz]

I've got that one and its big brother which measures 1-2". Infinitely better than a caliper - which can never accurately measure an ID.

 

[tattoomike68]

On small diameters I used to mill the part in dead nuts in half and use an optical comparator.

the machines made parts in 2-3 seconds so destroying a few ment nothing.

 

[DICKEYBIRD]

Yup, got the pair from Enco (Chinese) as well and really like them. I think they're a steal for the price. The small one even has carbide jaws for long life.

My hole/shaft fit accuracy level went up a bunch when I started using them instead of calipers.

 

[mklotz]

Dickeybird,

Apropos of this thread, you may want to take a look at something else I posted today.

http://www.homemodelenginemachinist.com/index.php?topic=1259.msg9039#new

 

[BobWarfield]

Good find!

I have a Starret in the 0.2-1.2 range. After a long search, I snagged it on eBay for a price slightly more than what Enco offers.

I echo the sentiment that they beat the heck out of calipers.

Best,

BW

 

[rake60]

As usual I find a BUY after I've spent my money... :-\

In my eBay browsing today I saw this Buy It Now listing.
.2 to 1.2 Inside Micrometer

I have a set of China Import 0 to 6" outside mics that I purchased
from this vendor that I am very happy with!
I just ordered one of their .2 to 1.2 inside mics to give it a looking over.
I will post a review of it as soon as I receive it.

Rick

 

[BMyers]

I bought one also. Good price.

 

[rake60]

I received that cheap little .02 to 1.2 inside mic from CME Tools today.

4 days to arrive. The quality for the price is something I've come
to expect from them. It turns smoothly and has a good feel to it when
measuring a fit.

Checking the "zero" with the standard looks like this.

Huh? is that off .0002"? I'll need to adjust that right away! LOL
I think it's a very good deal!

Rick

 

[BobWarfield]

Nice mic Rick!

BW

 

[BMyers]

Mine showed up today too. Off .001. How do you adjust them ? I haven't figured that out yet. Nice tool for the money

 

[rake60]

Mine showed up today too. Off .001. How do you adjust them ? I haven't figured that out yet. Nice tool for the money

This may be of some help to you.
http://its.fvtc.edu/MachShop1/Inspection/AdjustMic.htm

 

[BMyers]

Thanks Rake,
I got brave and figured it out. Spin off the cap at the end of the movable jaw and adjust the screw under said cap.

 

[rake60]

BMyers

I'm not exactly sure I know what screw your talking about.
"Zeroing" a mic should be done by using the small spanner wrench that
come with the mic to rotate the barrel sleeve to read an absolute "zero"
when checked to the standard.

There is also an adjustable spindle nut under the thimble.
It's purpose is to take up any slop or free play in the 40 threads per inch
rolled thread of the thimble.

Does your new mic still turn freely?

Rick

 

[BMyers]

Rake,
Boy I feel silly. I have an old set of Lufkin mics that zero out strangely. I forget that 99.9% of mics zero by rotating the barrel. And it does turn and work nicely. better than me :

 

[ChooChooMike]

Got the inside mic today. Grrrrrrrrrrrr, when all the way closed, it's 0.007 off. Does that make sense ? Well, it is Chinese made after all Didn't think it be that bad. Guess I'll have to reset it and see if it measures ok.

Hmmmm, although when I line up the 0.2 line and 0 on the thimble, and measure across the pins with my caliper, it's 0.201. so looks like all the way closed is NOT 0.200, more like 0.184

Guess I'm used to a conventional mic where all the way closed is 0.0

Odd mic - must be left-hand threaded, turns spindle CW to open the jaws and CCW to open.

Mike

 

[rake60]

Mike
The inside mics of this type do work exactly opposite of an outside mic.
The do have the same 40 TPI right hand thread as an outside mic,
but we are used to seeing the spindle move when we turn the thimble.
With an inside mic it's the barrel that moves.

Checking the "Zero" is also backwards.
To set "Zero" place the .200 standard over the pins and turn the
thimble CW using the ratchet ratchet at the end of the thimble while
gently rotating the standard to to be sure it is square on the pins.
When the ratchet clicks, you set your "0" - ".200" at that point by using the
supplied spanner wrench to turn the barrel to a perfect "0" reading.

The very first time I ever used one of these mics I had borrowed it from a
coworker. I couldn't get it to open up. I asked the owner is there was something
wrong with it. When he saw I had it cranked in tight, he grabbed it away from me
with the words, "Well FIRST off, you have to be smarter than what your working with!".
(Nice guy with gift for teaching!) :
But I did learn how to use it very quickly that day....

Rick

 

[BobWarfield]

Missed the calibration info the first time out.

I have calibrated my conventional mics in this way, though I didn't know about the nut up inside. Good extra info.

Now I've got a digital mic that's acting up. It seems like it's set up for a spanner too. Does anyone know if they calibrate the same way?

I hate to take it apart and mess things up, but I guess I'll do that next if nobody can confirm.

Best,

BW

 

[ChooChooMike]

Rick,

Checking the "Zero" is also backwards.
To set "Zero" place the .200 standard over the pins and turn the
thimble CW using the ratchet ratchet at the end of the thimble while
gently rotating the standard to to be sure it is square on the pins.
When the ratchet clicks, you set your "0" - ".200" at that point by using the
supplied spanner wrench to turn the barrel to a perfect "0" reading.

Thanks for the tip ! I put the mic on the standard and it's approx 0.001 off, I'll tend to that later. Guess I had assummed that all the way closed would have been 0.200 more like a conventional mic is 0.000 all the way closed. Of course you can't measure a 0.200 i.d. hole accurately if the mic only goes to 0.200 min ....

the words, "Well FIRST off, you have to be smarter than what your working with!". (Nice guy with gift for teaching!) :
But I did learn how to use it very quickly that day....

Rick

Amazing how lessons come along like that in the most off-hand ways I've had many of those myself. A simple sentence came put you in your place and/or make you stop and think !

Mike

 

[tel]

I received that cheap little .02 to 1.2 inside mic from CME Tools today.

4 days to arrive. The quality for the price is something I've come
to expect from them. It turns smoothly and has a good feel to it when
measuring a fit.

Checking the "zero" with the standard looks like this.

Huh? is that off .0002"? I'll need to adjust that right away! LOL
I think it's a very good deal!

Rick

Mine arrived today - 8 days from the US of A to beautiful downtown Oz - I thought that was pretty good. AND I'm pretty impressed with the instrument too.