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mbensema
10-25-2002, 09:35 PM
I'm looking to get a set of large micrometers for checking bearing seats on large shafts and would like to hear your pro and con comments on individual micrometer sets compared to the ones that have a single frame with different sized anvils to give you the large range. Do these single frame sets have the same repeatable accuracy as the ones meant for a single size range?

Thanks,

Mike

docsteve66
10-25-2002, 11:40 PM
Ihave seen them used on jet engines. I have a set. Seldom use them because of the size. The set I have comes with a set of calibration rods. The add on anvils are adjustable, the accuracy is very good.

I had a calibration shop in my group. All traceable to master standards. Mics were adjusted by measuring a standard, moving the thible (loosed in various ways) until the mic read the proper length. simple job. Point is: you need a standard of some sort, check them often. I have not heard of troubles because the screw was worn in one place, but I guess it happens. one nice thing about the big frame is that you can get it around a big object, insert the anvil and then measure.
Steve

SGW
10-26-2002, 09:48 AM
Docsteve66 raises a good point: it tends to be inconvenient to have a 6" micrometer frame when you're measuring 1"-2", accurate or not.

However, in my case at least I very seldom need a micrometer larger than 3". I have individual micrometers that cover 0-3". In my case, I think it would make sense -- if I ever have the money -- to get an interchangable anvil micrometer to handle 3"-6". I'd use it so infrequently, the cost savings would make any minor inconvenience worthwhile. As the dimensions get larger, too, the disparity between frame size and what you're measuring becomes less of a consideration.

[This message has been edited by SGW (edited 10-26-2002).]

mbensema
10-26-2002, 10:21 AM
Thanks for your input. I'm looking at a set of 150-300mm mics to check bearing seats at my customers when they are doing overhauls. I already have individual mics in the smaller sizes that I use often. Since I may be traveling by air, I want to get as small a set as possible and the interchangeable one looks like it would work much better for that purpose. I'll make sure the set has a good set of standards as well. Thanks again,

Mike

Thrud
10-26-2002, 09:16 PM
mbensema:
You will find that the interchangable anvil mics are not as accurate as the individual mics. I have a 0-6 and never use it, I use the individuals all the time (.ooo1 thimbles). I also have the large ones to 10" but rarely use them. It all boils down to your personal preferance - I find screwing around all the time with the rods is too much trouble. A boxed set to 12" is not all that big...

docsteve66
10-27-2002, 07:57 PM
My Starrett 2 to 6 " is trustworthy to .0001. I have a set of "sherr-tumico" inside micks (with replaceable rods in 1/2" increments. I trust it to no more than .001 because it is too easy to leave some thing between the mating surfaces. So (seldom needed) I "calibrate" it by using the Starrett outside mike when i want to be right on. its best use is carrying the same dimension from place to place- My "Arkansas" ruler again http://bbs.homeshopmachinist.net//smile.gif.
I figure nothing is 100% accurate, nothing is 100% trustworthy but am na has got to believe in SOMETHING!.
Steve
PS. when I really want to be sure, i let the part "rest" till its room temp and measuring tools are same temp. It's suprising how long a big (what ever that means) chunk of iron takes to get cool (or warm) to its core.

mbensema
10-27-2002, 10:25 PM
I guess I have some more thinking to do about this. I was leaning towards the replaceable anvils to save on space, but if it's too much of a pain, they would only end up collecting dust. I'm not going to use these mics very often, and probably not the entire range, so I may be better off buying the size I need when I need it instead of the complete set. Ebay seems to have an endless supply at decent prices.

Thanks again,

Mike

Thrud
10-28-2002, 07:03 PM
Mike
...and no one seems to want them either. So they go cheap! (Bonus http://bbs.homeshopmachinist.net//biggrin.gif)

[This message has been edited by Thrud (edited 10-28-2002).]

mbensema
10-28-2002, 09:39 PM
I made a good deal on a couple metric micrometers last week. Nobody was bidding on them, so i made a lowball offer for 2 of the ones she was selling and she accepted. I noticed another auction where some large metric micrometers didn't get bid on last week and they are back in at the same prices. I'm thinking about putting in a low offer on those too. This way is more fun then the real auction http://bbs.homeshopmachinist.net//wink.gif

Mike

Thrud
10-30-2002, 04:34 AM
Mike
Yeah, it sure is great when people see the "M" word and run for the hills. Leaves more eyeballs for us vultures fight over!:G

I bought a really, really old Starett #454 12" height gage - hand lettered leather covered wood case - blue velvet interior. A beauty. It has some old toolmakers name scrawled in it (didn't like that part). I hunk o' history. Got it from an antique dealer who thought he got the better deal - not a chance... http://bbs.homeshopmachinist.net//biggrin.gif

Tel
10-30-2002, 07:33 AM
Ho! Coupla weeks back I got a 'damaged' Mitutoyo 0 -2" for A$7.50. The damage?? The spindle lock was on - otherwise unmarked & complete in wooden case. http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

docsteve66
10-30-2002, 11:35 AM
TEL, This a straight question, exposing my ignorance- not trying to catch your mistake. IS your mike really 0-2" or is it 1 to 2 inch?

Steve

Thrud
10-30-2002, 01:57 PM
Steve

They did at one time have actual 0-2" micrometers - took forever to unscrew the thimble. Have not seen one in 30 years+.

Might have been Starrett. They make some strange stuff at times.

Tel
10-31-2002, 07:24 AM
A genuwine 0 - 2" Mitutoyo Doc. Has a little clamp thingy that carrys a 1" anvil & slips over the standing anvil - pretty quick to set up & very accurate. Also has a little clip on magnifier so as us old codgers can read the thimble easier.