# How to judge the quality of micrometers and calipers



## starr256 (Jun 15, 2018)

There are numerable threads on what micrometers and calipers should be acquired. However, the majority of the responders are machinists stateing what the have bought and what they thought of the purchase.Unfortunately,  Its all a discussion about name name brand or country of origin. What I want to know is what makes a B&S or Mitutoyo $100+ micrometer better than a $15 knock off?  I mean, from a novice's view point, when starting out, does it really matter? What are the characteristics that determine the quality difference? What are the minimum qualities one should look for?


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## Eddyde (Jun 15, 2018)

It depends on how accurate the work you are doing needs to be. If you really need to measure +- 1/1000" or less, a micrometer is the way to go. If the tolerances can be a more then that, a dial or digital caliper will suffice.  IMHO it pays to get a quality instrument, that doesn't mean it has to be a big name brand but cheap-o junk is pretty much worthless.


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## starr256 (Jun 15, 2018)

How do I tell the difference? That's what is missing.


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## T Bredehoft (Jun 15, 2018)

Inexpensive Mikes may not have the 'feel' of a quality mike. When measuring, one feels (learns, knows)  the friction in the thimble as it turns free, when it encounters resistance (touches both sides of the piece being measured), that friction changes. If the friction in the thimble is high, that touch point can be lost.


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## Charles Spencer (Jun 15, 2018)

I originally bought an off-brand micrometer over forty years ago.  It worked.  But over the years I got micrometers, either Brown and Sharpe or Starrett, that I carefully keep in wooden boxes.  Two years ago I bought an inexpensive Chinese micrometer to take measurements of parts while they were still on the lathe and protect my more expensive ones.  I disassembled it, cleaned a couple of sharp edges with emery cloth, went over the surfaces with steel wool, and lightly oiled it.  I then compared its accuracy using several different blocks.  I didn't find any noticeable difference from my better micrometers.


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## TerryH (Jun 15, 2018)

I'm a reloader and through a discussion on some discreteness that I was seeing it was mentioned that it was likely the $20 Neiko calipers that I was using. I bought a set of Mitutoyo's to be for sure. The feel and general quality of the Mitutoyo calipers is head and shoulders above the Neiko calipers but with that being said I found no difference in measurements between the two. However, I reach for the Mitutoyo's virtually 100% of the time.


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## mikey (Jun 15, 2018)

starr256 said:


> How do I tell the difference? That's what is missing.



I doubt you will SEE a difference. Precision mics have precision rolled threads, hardened and lapped faces and engraved dials. I don't own Chinese measuring tools so I can't compare but my Swiss and German mics are very accurate and have remained so for decades. There is a good chance that a new import mic will be fine.  For how long I cannot say.


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## benmychree (Jun 15, 2018)

I bought my Starrett mikes and other tools back in the 1960s, and with daily use for all those years, (at least until retirement) they are still as accurate as I can perceive. nowadays they get used less often ---- but still on duty.  If I wanted a quality mike, I'd buy a used one on E Bay, either Starrett or Brown & Sharpe, looking very carefully at the pictures for possible abuse, and buy from a seller that accepts returns; I see very many smaller mics starting at around $25; they are a drug on the market ---- for every one, count a passed machinist.


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## Bob Korves (Jun 15, 2018)

When you NEED to get a measurement as correct as possible, and especially if you are working commercially on parts with a lot of expensive work hours already invested in them, being able to trust your feel and judgement, and get it right the first time for sure, well made mics and other machine tools will inspire confidence in your first measurement, not choosing the most repeated number seen from five or more tries.


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## DAT510 (Jun 15, 2018)

With Micrometers I've not really seen a difference.  As others have mentioned the feel of generics can vary.  I have had generic micrometers right out of the box, not be zero'd.  But once adjusted for zero, they've been fine.

I have found with Calipers (digital in my case), there can be differences in measurement the wider they are opened.  I think it's a tolerance stack-up issue.  My two no name digital calipers start to vary by a few 0.001" past about 3", as compared to my Mitutoyo 6" Digimatic.  I have confidence in the Mitutoyo is as it's be calibrated multiple times. 

As I don't measure something for super accuracy with calipers, this is not an issue.  If I need accuracy with something that large, I use a big Micrometer.


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## Bob Korves (Jun 15, 2018)

If the error grows incrementally with opening the mic further, then the screw lead is in error.  There is no fixing that, it must be lived with or replaced.


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## Chuck K (Jun 15, 2018)

I like the craftsman mics from back in the 70s.  I'm not sure who made them but they feel nice and they can be had cheap on ebay.   I have the big name mics but I always reach for the Craftsman.


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## cascao (Jun 17, 2018)

measure same part many times. It have to give same reading all times. (or it will make you crazy)
smoothness on movement. (it will give you better feeling when taking a measurement)
battery consumption (seems like cheap ones are avid battery consumers)
surface finish (if you care)
durability (long term investment)
Trust (sometimes, things get confusing. You need to trust your meassuring tools)
After all, if you can get it calibrated by a specialized company, it should be good to go.


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