Calliper - Dial reading

Am I being really thick here. Thinking of buying a METRIC Dial calliper, but puzzled by how to read it. Imperial is simple, what you see is what it is. However METRIC dials have a dial marked in divisions of 0.02mm. The dial is marked 0-10,0-10.

So for a complete revolution of the dial = 2mm? .

Edited By Speedy Builder5 on 02/11/2020 16:06:51

Yep 2 mm / rev is normal.

Fundamentally a question of mechanical practicality.

1 mm is near as dammit 40 thou so a 2 mm per rev dial corresponds to 80 thou / 0.08 inch so the sensitivity / accuracy of metric and imperial dial callipers is about the same.

1 mm per rev is too sensitive to be sensibly practical. The rack and gear teeh become silly tiny.

Clive

Clive has it, spot-on

The Metric dial is just two 180° scales

MichaelG.

Why not save yourself the agonizing over the metric dial caliper and just get a digital? The cost is not much different, the digital has numbers big enough to read and with a quick push of a button becomes an imperial caliper. Very easy to set a new zero as when you are turning to a specific dimension you can set that dimension as a zero and read how much needs to be removed to get the intended dimension.

Stick with your original plan to purchase a dial caliper, SpeedyBuilder5! I bought a digital caliper 18 months or so ago and it's just so flimsy compared with an imperial digital caliper purchased 40+ years ago, which is still in v.g.c. A few weeks after purchase I had to return the instrument to the manufacturer for a warranty claim, as the plastic body developed a split, and I don't consider myself particularly heavy-handed with instruments. The replacement's held up OK to date, but overall the instrument just doesn't feel as substantial or as nice to use as its imperial predecessor.

Edited By Tim Hammond on 02/11/2020 20:31:48

Dial callipers don't have a battery to go flat on you when needed.

I'm prejudiced. With maybe 50 or so micrometers, verniers, callipers and similar about the place going electronic isn't going the happen!

One day I should do a proper census.

Clive

"Dial callipers don't have a battery to go flat on you when needed."

Absolutely! And will the electronics still be in good working order a score or more years down the line?

Nice little training/publicity video from Starrett here;

Edited By peak4 on 02/11/2020 21:09:22

If your eyesight starts to go bad the fact that you have to replace a battery occasionally will not bother you so much as not being able to see the numbers on the dial nor the lines on the vernier. I have to replace the battery about once a year on each of my digital calipers. Since I know that, I keep a few spares on hand.

Since I have a variety of different callipers, maybe I can comment. The dial caliper I have is Imperial, and works fine, but is prone to getting tiny chips of metal in the rack. So it is good for checking things in a clean place, not so good in the workshop, especially if brass or cast iron is being machined.

The digital ones are easy to read, although they too can suffer from cast iron. What happens is that a conductive coating of graphite gets deposited along the surface, and this interferes with the capacitive readout of the position. I did have a small set, about four inches long. That was very handy for confined spaces, but the electronics died.

The actual verniers don't get used much, because it is harder to get an accurate reading from them. One of them has one side calibrated in fractions, down to 1/128 or so, that is quite handy for checking sizes of fractional Imperial items.

John

Why dial type? I had a cheaper digital, but battery contacts corroded and after several attempts to clean them, used an external power supply and butchered it for a Z axis on the mill. I have a vernier metric calliper, one side metric, the other side fractional measuring in 1/128ths ! I can manage verniers Ok (Bit like using log tables) but have to admit that the dial is easier to read. I am predominantly an Imperial bloke living in Metric land and can't be bothered removing batteries to stop them leaking on a set of callipers that I would use perhaps once a month!

Have you noticed that medical thermometers are mostly digital. Being in general good health, we needed to use our the other day - Flat battery !! Fat lot of use that was.

Bob

Flat battery & no replacement to hand? pop the battery out and warm it up gently (i.e. not with a blowtorch !) 5 mins on a hot radiator will usually get it going for a short session and get you out of a fix. Worked for me numerous times in an 'emergency'.

I guessing our digital thermometer has a flat battery, my youngest son is 28 and he was probably still in single digits last time it was used

Mike

Do batteries come under "Essential supplies"? Sadly for those who only use electronic measuring and display devices, the ability to count more than twenty, without having to remove shoes, could be a problem. Surprising the number who were away from skool the day they did maffs.

Regards Ian.

I have two digital calipers, both of which "eat" batteries, and one of which is somewhat iffy in respect of readings. I also have a Starrett 6inch/150mm dial caliper with a 0.01mm resolution which is very nice to use. Unfortunately, the Starrett & the digitals are a bit too long for easy use around the lathe so I also have a "White Face" 4 inch/100mm 0.02mm resulution dial caliper. This is not the best, it does feel a bit rough on the rack but is certainly easiest around the lathe. Finally, I have a 6inch/150mm 0.05mm resolution vernier caliper which due to its resolution is only used for initial measurements, but it is nice & smooth in operation. And, of course, it does require some optical magnification to determine the actual reading!

In general then, the "White Face" 100mm is the first choice with the Starrett being second. This is purely because of convenience. The digitals just sit there, doing nothing!

One point that has to be mentioned is that all these devices vary in their absolute accuracy, not much, it's true, but it does mean that if a measurement is required to be consistent, then the same device should be used every time. As it happens, I do have the Mitutoyo micrometer standards for 25, 50 & 75mm so I can, if I need to do, perform a comparison check, albeit only at those three sizes.

Peter G. Shaw

Dial calipers have a nasty habit of jumping if dropped, the fix for Mitutoyo is simple and by coincidence I have a video of it on my youtube channel. Just ignore the badgers, it's in there somewhere. 😴

I'd be wary of buying one of the £35 "Mitutoyo" digital calipers from the well know auction site!

I did pick up an "as new" 12" Japanese dial caliper by Kanon for very occasional use, probably from the 70's. Its a lovely thing to use but when I looked closely contamination of the rack could be a real issue.

I have a 6" digital caliper made by Linear that came from Cromwell when I got huge discount through work, unfortunately that won't happen anymore, that probably wants relegating to second tier use so I've been keeping my eye open for a bargain! Second hand calipers are a bit of a lottery, wear on the measuring faces being the main concern.

A micrometer is always my first choice for accurate measuring where possible.