Question about micrometer

xkatx · Jul 30, 2018

Hello,

I bought a cheap used Mitutoyo micrometer and it measures from 0 to 30.96mm. Is this normal or is the micrometer inaccurate? On the body it's written 0 - 30mm so I was thinking that 30mm is the maximum value I should see on the display...

I don't have any blocks that are precisely machined to test it on, but I did measure a supposedly 12mm cube magnet and the result on the display was between 11.99 and 12.01

DMF_TomB · Jul 30, 2018

xkatx said:
Hello,

I bought a cheap used Mitutoyo micrometer and it measures from 0 to 30.96mm. Is this normal or is the micrometer inaccurate? On the body it's written 0 - 30mm so I was thinking that 30mm is the maximum value I should see on the display...

I don't have any blocks that are precisely machined to test it on, but I did measure a supposedly 12mm cube magnet and the result on the display was between 11.99 and 12.01

.
you check with gage blocks
.
PS real Mitutoyo micrometers are not cheap. generally very good quality
.
some stuff can be counterfeit. people put different name on a tool and charge more money. ebay full of counterfeit cheap stuff. you can buy a $5 Rolex watch but it aint a real Rolex

xkatx · Jul 30, 2018

I meant that I bought it for a cheap price, compared to the retail price. And it was not new.
I don't think it's a counterfeit because it looks nicely made.
But I do find it odd that it measures 1mm beyond 30mm.
This is the model I have:
https://ecatalog.mitutoyo.com/cmimages/003/310/422-411.jpg

Danny VanVoorn · Jul 30, 2018

It seems a little odd the 0-30mm, most metric mics I've had in hand (only a few) were 0-25mm, 25-50mm etc..
I don't know what the problem is exactly, there are micrometer standards specifically for checking mics. Checking a magnetic cube seems like a bad idea to me, might induce some magnetism in the tool that could be later used on ferrous materials? DMFTomB has the right idea with gage blocks or a ball bearing with a known diameter would work also.
Dan

Danny VanVoorn · Jul 30, 2018

xkatx said:
I meant that I bought it for a cheap price, compared to the retail price. And it was not new.
I don't think it's a counterfeit because it looks nicely made.
But I do find it odd that it measures 1mm beyond 30mm.
This is the model I have:
https://ecatalog.mitutoyo.com/cmimages/003/310/422-411.jpg

Most mics if not all I've had measure a little over the stated range, now if it measures below the stated range you have a real problem?
Dan

michiganbuck · Jul 30, 2018

Measuring a magnet is poor use of a micrometer. In great shape zero set is OK at best, but. Bouncing off zero (closed to zero) is hard on a micrometer. Zero to zero may not be accurate due to wear in the screw thread.
Jo Blocks are good to their rating and very parallel on the gauge side...So are best for setting a comparison to a desired size. It is best to have a flat test device..

*Perhaps take a piece of flat and parallel steel something to a local shop and have them measure it and then scribe that size on your new gauge.

For very close work you make a jo block stack to the desired size. set your micrometer to that being the zreo and test the part to the size,, but yes you need a whole jo block set to do that.

xkatx · Jul 30, 2018

I don't know where I could find some gauge blocks that are cheaper than the mic.
I saw that Mitutoyo sells them for like 1000 Euro / a piece. That's insane.
But a ball bearing I can find

Dumpster_diving · Jul 30, 2018

I don't think it's unusual for a mic to have a range that's just a little past it's maximum advertised value.

tomato coupe · Jul 30, 2018

xkatx said:
Hello,

I bought a cheap used Mitutoyo micrometer and it measures from 0 to 30.96mm. Is this normal or is the micrometer inaccurate? On the body it's written 0 - 30mm so I was thinking that 30mm is the maximum value I should see on the display...

My Brown & Sharpe 0-30 only goes to 30.8, so yours must be broken. Send it to me and I'll dispose of it for you.

The real Leigh · Jul 30, 2018

I see nothing wrong with it measuring over nominal.

What would you expect in order to measure a 30mm part that's over-tolerance, with enough extra opening to get the mic on and off the part without a hassle?

- Leigh

Gordon B. Clarke · Jul 30, 2018

xkatx said:
Hello,

I bought a cheap used Mitutoyo micrometer and it measures from 0 to 30.96mm. Is this normal or is the micrometer inaccurate? On the body it's written 0 - 30mm so I was thinking that 30mm is the maximum value I should see on the display...

I don't have any blocks that are precisely machined to test it on, but I did measure a supposedly 12mm cube magnet and the result on the display was between 11.99 and 12.01

Mitutoyo has a 0 - 30mm digital micrometer. Not too common as it is special and costs a good bit more than a 0 - 25mm. It's "faster" than a normal micrometer.

Mitutoyo Digital external micrometer IP54 �-3� mm

Digital micrometers, like digital calipers, always show more than the stated value.

I don't know how much you paid but you probably got a "bargain". Much better than a standard 0 - 25mm.

If you want to know how accurate it is buy a micrometer 25mm standard and they are good to better than ±0.001mm. They're not expensive.

xkatx · Jul 31, 2018

Thanks everyone. I didn't know that micrometers can measure above the stated range.
So I guess there is a chance that it's accurate enough.
I only bought it because it seemed cheap compared to prices that I saw online (85$ vs 800$).
Otherwise I would have got a new unbranded/chinese one for the same price from a local store.

michiganbuck · Jul 31, 2018

Doing .001 inch work a simple brand-name micrometer may be best..that way one can save high precision measuring tools for close work.

.003MM is about .0001 inch so good to save it for close work.

.001mm about .000039 inch so OP's micrometer not the hack job micrometer.

I have seen China micrometers that did not lock/set zero very well so the apprentice that bought a three micrometer set would have to check a jo block after each use.
An old clunker name brand micrometer was much better.

Gordon B. Clarke · Jul 31, 2018

xkatx said:
Thanks everyone. I didn't know that micrometers can measure above the stated range.
So I guess there is a chance that it's accurate enough.
I only bought it because it seemed cheap compared to prices that I saw online (85$ vs 800$).
Otherwise I would have got a new unbranded/chinese one for the same price from a local store.

I don't know how old the one is you have but I looked at the price as it was 12 years ago. Two types - numbers 293-661 and -666.

Price 12 years ago $420. Bet you've made some people jealous

Gordon B. Clarke · Jul 31, 2018

michiganbuck said:
Doing .001 inch work a simple brand-name micrometer may be best..that way one can save high precision measuring tools for close work.

.003MM is about .0001 inch so good to save it for close work.

.001mm about .000039 inch so OP's micrometer not the hack job micrometer.

I have seen China micrometers that did not lock/set zero very well so the apprentice that bought a three micrometer set would have to check a jo block after each use.
An old clunker name brand micrometer was much better.

I have a Chinese 0-25 and a 25-50mm digital micrometer. Both are guaranteed accurate to ±0.002mm but are in fact accurate to ±0.001mm. They weren't cheap but still cost less than a Mitutoyo or any other top brand.

michiganbuck · Jul 31, 2018

Agree good stuff from China is good stuff.
and poor quality stuff from anyplace is poor stuff.
I was not knocking all China tools but did know a few apprentices who should have tossed brand new junk China micrometers in the scrap bin after day one.. They looked very nice , seemed good materials with carbide anvils but would not stay locked..

One a German guy and sharp got suckered in to buy that junk...Should have asked his journeyman(me ) before buying such junk.

Perhaps this is the set? HFS - 3" Micrometer Set .1" Carbide Ground Standards (Plastic Case) 819316327 | eBay

Perhaps they improved the locking feature..perhaps still junk?

I made a one inch micrometer in high school machine shop..but did not have small number stamps so no numbers..even made the 40 tap out of drill rod and it worked..

xkatx · Jul 31, 2018

My experience with China stuff is actually very good.
I buy lots of things from chinese sellers on ebay, like oil lighters, folding knives, flashlights.
The trick is to avoid cheaper products and go for the ones with higher prices, even if they appear to look similar in the pictures.

One time I bought two lipo battery voltage testers. One was like 1$ and the other almost 3$. When they arrived, I was surprised to find that the higher priced one looked better made overall and the LCD was way brighter. Voltage readings were slightly different too, but I can't tell which one is more accurate.
Same with a bullet oil lighter. They looked exactly the same in pictures but one was 2$ and one 10$. The cheaper one was thin aluminium coated with brass-like color and the other one was actual brass and very thick.
Folding knives above $50 are also very nice and smooth

Gordon B. Clarke said:
I don't know how old the one is you have but I looked at the price as it was 12 years ago. Two types - numbers 293-661 and -666.

Price 12 years ago $420. Bet you've made some people jealous

Mine is the version with the blades. The guy had some models with round tips too, but he already sold them by the time I contacted him. (I would have preferred those)

Gordon B. Clarke · Jul 31, 2018

michiganbuck said:
Agree good stuff from China is good stuff.
and poor quality stuff from anyplace is poor stuff.
I was not knocking all China tools but did know a few apprentices who should have tossed brand new junk China micrometers in the scrap bin after day one.. They looked very nice , seemed good materials with carbide anvils but would not stay locked..

Agreed. I think much of the problem in the USA is that so many seem to be expected to buy their own measuring tools. Here when shops and companies buy it gets written off and is tax deductible. Another (important) factor is that in general company property gets handled with respect. Part of that could be because if you don't you'll soon be looking for another job.

Screwmachine · Jul 31, 2018

Every mic I've ever used could go well over max stated measurement. 0-25 (mm) will do 26 nearly, 25-50 same on up. It's normal. A 10" lathe isn't going to crash if you put a 20.005" part in it. Schaublin made their 102 lathes so a 200mm part can swing free.

I use mostly Mitutoyo stuff even in the land of Tesa but both will measure accurately a mm or so over listed size (under too on big mics).

Gordon B. Clarke · Aug 1, 2018

Screwmachine said:
Every mic I've ever used could go well over max stated measurement. 0-25 (mm) will do 26 nearly, 25-50 same on up. It's normal. A 10" lathe isn't going to crash if you put a 20.005" part in it. Schaublin made their 102 lathes so a 200mm part can swing free.

I use mostly Mitutoyo stuff even in the land of Tesa but both will measure accurately a mm or so over listed size (under too on big mics).

As Leigh pointed out in post #10 it'd be nigh on impossible to measure to the maximum stated if "whatever" didn't go above.

An everyday example is the speedometer in your car. Anyone ever drove faster or even near the max shown? Down a steep hill and not in gear doesn't count

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