Vernier Calipers, anyone use them?

[Dickie]

Originally Posted by Herald1360

............ Not really any more precise than a steel ruler, but useful nonetheless.

That's what I would have said, but if you take care and don't bend the jaws(!) its pretty good. Though I certainly wouldn't rely on it for a critical measurement.
EG I took an M3 drill bit which checked out at 2.955mm using a Mitutoyo micrometer. It resulted in:


2.95mm on the cheapo electronic one
2.95mm on the stainless steel mauser
3.0mm on the plastic one.


If I recall correctly, these were given out in the 70s or 80s when the only other calipers around were high quality and expensive. Thus quite a novelty. With the mass destruction of goods-in inspection and model shop departments plenty of cheap second hand ones appeared.

[ajgriff]

Prompted by this thread I started to research the company that made my rather ancient vernier caliper and came across this interesting educational document produced by Mitutoyo and entitled 'The Origin and Evolution of Calipers':

https://www.mitutoyo.co.jp/eng/suppo.../08/E12029.pdf

My caliper is featured in Fig 42 on page 20 and apparently dates from around 1900. It was acquired from a used tool stall at a market many years ago. To be honest it's not used very often as I find a steel rule adequate for most things.

Alan

[ajgriff]

When I fished out my Rawco calliper I was rather ashamed of its somewhat grubby appearance so I spruced it up a little to pose for the attached photos. I’m using the traditional UK spelling of calliper as this one was made by a little known 19th century London tool maker and it seems more appropriate than the commonly seen US spelling with no double letter.

Despite the slight surface corrosion the graduations are still legible and in terms of accuracy it stands up well when compared to a selection of micrometers. It has metric and imperial scales which is handy now and then. The depth bar is probably the thing I use most often and this ties in nicely with the fact that Mitutoyo’s researchers believe that it’s one of the earliest examples of this type of calliper incorporating such a feature (see link in preceding post). The only other reference I can find to Rawco is sketchy and relates to small lathes.

One thing about the calliper which I hadn’t really noticed before is the non-matching locking knobs. Looking at Fig 42 in Mitutoyo’s document suggests that the vernier locking knob has been replaced at some point in the distant past. However, now that I know a little more about this Rawco calliper’s provenance I will treat it with renewed respect. My thanks to John for starting this thread as without it I wouldn’t have been prompted to undertake some research.

Are there any other callipers out there with a bit of history associated with them?

Alan

[emeritus]

Here's my three.

The big one, ~12" useable range, is ex-Marconi Crompton Works, bought at auction, complete with very oily and slightly damaged wooden case, when the site closed. A couple of 'thou wear at the tips, fine about half an inch in. Metric and Imperial, Made by Chesterman, dated AM 1943. Not used much. Lives in the garage.

The stainless steel one (French) I inherited from my late brother-in-law. Metric only, has a useful depth gauge. It's the one I use most. Lives in my desk indoors.

The plastic one came free with Dad's "Practical Householder" circa 1960. Imperial and metric, but only has an imperial vernier scale. Useful for checking button cell dimensions.

On using the callipers and my Mitutoyo micrometer to measure a drill shank, all agree with each other within the limits of their respective resolutions. Remarkable accuracy for a ~60 year old plastic freebee.

Just to show that precision measuring instruments with digital readouts are not new, here a scan of an advert for a digital micrometer from the 1899 edition of "Molesworth's Pocket Book", although the 0.0001" figures do have to be read from a scale. I can't say I have ever come across such an instrument in the flesh.