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Which micrometers?

C

Chris152

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I'm drawn to a used set of these, for sale nearby for a relatively low price (in very good condition, apparently):

But for a little more, I can buy the first four micrometers on this link (new), and I do think digital would be easier to work with:

Standard Digital Micrometer | Measuring Tools | Machine DRO - Machine DRO UK

Our extensive range of precision digital micrometer for standard and special measuring applications from big brands such as Moore and Wright and Mitutoyo
www.machine-dro.co.uk www.machine-dro.co.uk

Clearly the former is a better name, but in use, would you expect much difference? Accuracy, smoothness of movement etc?

Thanks for any thoughts, C.
 
I'd buy Mitutoyo without any hesitation. Bear in mind that there are a lot of copies out there that pretend to be Mitutoyo - more of a problem with calipers I think, but worth being aware of. I think there are a few websites around that help you spot copies.

If you're anything like me, the micrometer won't come out very often: it's something I use only when I need the extra precision (typically for trying to achieve specific fits, e.g. for bearings). However, when you need it, there's nothing else comparable and its worth having a good one.

I've got two 0-25 mm Mitutoyo micrometers (one digital, one micron-reading with a vernier scale) as well as a cheaper one I bought early in my metalworking career (buy cheap, buy twice...). The Mitutoyo ones are in a different league for smoothness and (more importantly) repeatability. They also measure to a finer resolution as they're both micron reading ones, although with μm you risk get into debates about how much temperature effects change the size of the thing you're measuring and also how consistent you are with turning the dial for a good measurement (it's worth getting a lot of practice with gauge blocks before you try to measure anything important).

I've also got a 25-50 mm micrometer (an old Moore & Wright one if memory serves me correctly). I can't remember the last time I used it: it's rare that I need to measure anything that big to such a high level of precision. I've never yet needed to measure anything bigger than 50 mm with accuracy greater than what I can do with a decent caliper and hence I've never acquired a 50-75 mm or 75-100 mm one.

If I were you, I'd spend the money on one really good Mitutoyo 0-25 mm micrometer and worry about larger sizes if and when you need one.
 
Thanks Al. Size is tricky, as one measurement will be (for eg) a piston diameter (so over 50mm); the next it's small bearings (as you say). We have plenty of old Imperial ones, but I'm hoping to get easy to use metric. As for the fake/ genuine article, that's a whole other can of worms!
 
Chris152 said:
Thanks Al. Size is tricky, as one measurement will be (for eg) a piston diameter (so over 50mm); the next it's small bearings (as you say). We have plenty of old Imperial ones, but I'm hoping to get easy to use metric. As for the fake/ genuine article, that's a whole other can of worms!
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Out of curiosity: for the piston, how do you intend to measure the bore (or are you making both bits to specified dimensions/tolerances?) For most big things that need to be accurate (including situations where I've done close sliding fits and interference fits) I just make the bore and then turn the fitting part to size (testing very regularly and taking extremely light passes with a very sharp but rounded nose HSS tool).
 
Dr.Al said:
Out of curiosity: for the piston, how do you intend to measure the bore (or are you making both bits to specified dimensions/tolerances?) For most big things that need to be accurate (including situations where I've done close sliding fits and interference fits) I just make the bore and then turn the fitting part to size (testing very regularly and taking extremely light passes with a very sharp but rounded nose HSS tool).
Click to expand...
It was to order the correct size piston for an engine rebuild - we measured the bore with a digital bore gauge, but wanted to check the old piston size to confirm what we needed. It turned out we needed to replace the 53.97mm piston with a 53.98 (C piston replaced with D piston, apparently - out of my depth here). So not as complex as what you're describing, but it was a struggle to get the right diameter of the old piston with our old micrometers. The lad will be doing more of these in future, so I thought some nice metric micrometers would be good.
 
Consider a Dial caliper.
Clear easy to read dial, no batteries to go flat.

Bod1.
 
Well, for what it is worth I have a number of Moore and Wright ones. A couple bought new for my EP1 and EP2. But some inherited from my grandfather. Bradford company originally I think.

Did everything I ever needed them to do. And not silly money. Old school - not digital. Only need them once in a year, but...
 
Bod1 said:
Consider a Dial caliper.
Clear easy to read dial, no batteries to go flat.
Click to expand...

An excellent book that I would recommend to anyone doing metalwork is "Machine Shop Trade Secrets" by James A. Harvey. It's not the cheapest book out there, but it has some excellent tips (it sometimes pops up on second-hand stores, so worth keeping an eye out). It's oriented around production work, but I learnt all sorts of things that I now use as a matter of course in the home workshop.

One tip from that book that's relevant (and which made me think of it) is #37:

Use digital calipers instead of dial calipers.

Once the gears skip in your dial calipers and you get an incorrect reading, you'll never fully trust them again.
Click to expand...

Get a set of Mitutoyo absolute digital calipers (preferably the metric-only ones that save you accidentally switching into the wrong units :)

Cheap digital calipers flatten batteries quickly and that can get very annoying. The battery in the Mitutoyo one lasts for yonks.

On Moore & Wright, the old ones are good, but steer clear of the modern ones.
 
Off tack. I remember being told by an ex Holman's (mining machinery) employee that he had gone into a workshop to clear it out when the place closed about 25 years ago and found a ........... I'll print it in case of doubt ............ one hundred and eight inch micrometer.
 
Phil Pascoe said:
Off tack. I remember being told by an ex Holman's (mining machinery) employee that he had gone into a workshop to clear it out when the place closed about 25 years ago and found a ........... I'll print it in case of doubt ............ one hundred and eight inch micrometer.
Click to expand...
That must have been a bit of a beast. 2.75 metres for those of us who prefer more modern units. Must have taken a couple of people to handle it and make sure measurements were done across the diameter and not slightly out!

I can't imagine it would have been used for super precision measurement: a 1°C change of temperature in a bit of steel of that size would change the diameter by about 30 μm (a bit over a thou for those stuck in the dark ages).
 
I quite enjoyed this video.


Maybe the real difference between Mitutoyo and the cheap Chinese ones is speed, frequency of use and longevity? (Pleasure of smooth, quality machining, too.) If that's the case, for occasional use, would it be fair to say that it makes far less difference than, for example, repeated daily use in a production workshop? The mechanical work my lad is doing is an aside, of sorts, so it'll be used occasionally.

Whatever happens, I think we're going to need some slip gauges to check for accuracy. Sorry to add in another question - is an average used set, or a cheap brand new set preferable? (Do they wear to become inaccurate?)
 
Dr.Al said:
That must have been a bit of a beast. 2.75 metres for those of us who prefer more modern units. Must have taken a couple of people to handle it and make sure measurements were done across the diameter and not slightly out!

I can't imagine it would have been used for super precision measurement: a 1°C change of temperature in a bit of steel of that size would change the diameter by about 30 μm (a bit over a thou for those stuck in the dark ages).
Click to expand...
It was to measure the bore of the largest cylinder they once made.
 
Dr.Al said:
That must have been a bit of a beast. 2.75 metres for those of us who prefer more modern units. Must have taken a couple of people to handle it and make sure measurements were done across the diameter and not slightly out!

I can't imagine it would have been used for super precision measurement: a 1°C change of temperature in a bit of steel of that size would change the diameter by about 30 μm (a bit over a thou for those stuck in the dark ages).
Click to expand...
Talk about the dark ages, when in my late teens I operated a 72" vertical boring mill. Making pump moulds. Needed help using the 8' vernier caliper, always did three measurements to ensure an accurate reading.
 
I just collected this set, just 2.5 years old and in perfect condition, sold by a nice young fella whose first engineering job bought it for him and he's now with another company. It's the lad's Christmas present, should do for him a good while :)

IMG_20241223_102008_edit_124545051575783.jpg

Thanks for the advice all.
 
Chris152 said:
I just collected this set, just 2.5 years old and in perfect condition, sold by a nice young fella whose first engineering job bought it for him and he's now with another company. It's the lad's Christmas present, should do for him a good while :)

View attachment 30877

Thanks for the advice all.
Click to expand...
I'm so glad you managed to get one without buying brand new.
Did I mention I've got a "moderately" big un ? :unsure:😊
Metric, 100mm max.
Just for reference the little un measures 1/2" max
Cheers, Andy
20241224_095917.jpg
 
If memory serves there's some really massive micrometers towards the end of this factory tour.

Interestingly I was talking to an acquaintance who does metrology at Nissan one day and he'd never heard of Starrett. I guess they use nothing but Mitutoyo.
 
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