Very accurate measuring references

[fizzy]

I received a nice new digital micrometer for Christmas. A DML chinese type. They have pretty good reviews so I was wondering what to test it on. I don't have the luxury of a set of test pieces.

Then I had an idea - old hard drive parts! I have loads in bits - usually to get the magnets out.

The platters are built to incredible tolerances.

Obviously I have no idea of the actual thickness but great for checking repeatability.

The one I measured was bang on 50 thou or 1.270mm - no deviation anywhere! Not bad for a £39 micrometer.

My Moore and Wright digital vernier(chinese I suspect) also read 1.27mm but obviously not as a high a resolution.

Has anyone else used hard drive parts for this kind of thing?

 

[Pete.]

Digital stuff is very accurate these days, so accurate in fact that they are easily affected by temperature. Does your new micrometer have two out-of-place looking plastic plates on the side of the bow? They are for holding it so the heat doesn't travel from your fingers into the micrometer frame too quickly.

 

[fizzy]

Yes - I guessed that is what they were for.
To be honest I think the quality of my vernier is even better than the mike - more than accurate enough for most people's needs and will measure up to 6" - very useful.

 

[rtbcomp]

I had a Hilka digital caliper (generic Chinese) it was useless, the zero point was unreliable, it kept switching between metric and imperial and would sometimes double the reading, sent it back for a refund.

I then bought a Moore & Wright digital caliper for pretty much the same money as the Hilka and it's been fine. From these people http://www.machine-dro.co.uk even got 6 spare batteries included.

I've used the ground steel bars that the heads in a HDD run on to check chuck run-out on my lathe & pillar drill.

 

[fizzy]

I had a Hilka digital caliper (generic Chinese) it was useless, the zero point was unreliable, it kept switching between metric and imperial and would sometimes double the reading, sent it back for a refund.

I then bought a Moore & Wright digital caliper for pretty much the same money as the Hilka and it's been fine. From these people http://www.machine-dro.co.uk even got 6 spare batteries included.

I've used the ground steel bars that the heads in a HDD run on to check chuck run-out on my lathe & pillar drill.

Yes that is where I bought mine. Very impressed with the quality. Feels much more expensive.
On offer at the moment - £23!

https://www.machine-dro.co.uk/150mm...r-moore-wright-basic-line-110-dbl-series.html

The Moore and Wright digital mike looks identical to the Chinese one I bought just twice the price. Probably better quality control but no point in spending that much more.

 

[Wozzaaah]

Under £26 posted from Amazon at the moment.

 

[merryman]

I have two "Chinese" ones that have stopped working, and use another at work which re-sets it's zero by itself sometimes. Also find engine bore measurements a mile out, though small sizes are pretty good. I think this is due to the aforementioned temperature problems.

 

[gaz1]

I bought one and its numbers was all over the place pretty useless to use like that

i have an older one so using that one and a magnifying glass to read it

 

[RichardM]

Hard drives - Yes they're great magnets, I strip mine for them.

If you have an old video player lying around the head is very accurately machined.

 

[anto44]

The dimensions of bearings are normally very accurate or use some feeler gauges stacked together.

 

[Pete.]

Old bearing races are great for all sorts of things. Spacers for machining/pressing/levelling etc plus as above they are very closely ground so make good measuring standards too. Set a bore gauge using one which is sized near to your target ID and use it as a standard to set your micrometer.

 

[waldershelf]

Years ago when the Chinese made digital Vernier's first came out I asked the guy who ran the standards room at work to run one against the (very) expensive callipers used on site, remarkably the thing was accurate enough to pass the required accuracy metrics. The build quality and robustness was no where near as good as the expensive ones and certainly wouldn't have lasted long out on the plant but I was very happy to have it in my garage at home knowing I had an accurate measure that I could rely on.