1/20Th Inch Markings On Ruler

[MTbowels]

I've got an engineer's 12 inch steel rule that has each inch divided up into 1/20th of an inch graduated divisions. Who would need to use such a scale? I do remember using wood rulers at school many years ago that had tenth of an inch divisions marked on it and I never managed to fathom out who would use them either!

Thank you

[jourdain2]

I've had cause to use 1/20th of an inch. Long ago in the mists of time, before everyone just pressed a button to use whichever typeface they wished, you drew out and measured your lettering. To be original today, I would start from the same place - OK, I'm probably old-fashioned and posters took days to design, but they were creative works.

[carrust]

I did an engineering apprenticeship & none of our rules were graduated in 20ths of an inch. They were 1/8, 1/16, 1/32 & 1/64.

[stuey]

Well, we certainly got some mileage out of this thread on measurement.

[alavahalf]

Did we really need the mileage..?

If you look at the first line of the original question ...

..... ''I've got an engineer's 12 inch steel rule'' .... and '' Who would need to use such a scale?

I'd guess you have answered your own question.

[carrust]

I've got a foot but don't use it as a rule;-)

[bert_h]

Stuey: // Talking about measuring, I think that ammunition is measured in 1/100ths of an inch. //

Well, some of it, like a '.45 Colt' or a '.44 Magnum' or a '.22 Beretta', but some others go down to thousandths, like a '.303 Lee-Enfield'.

[stuey]

Thanks, bert_h. So I guess that also describes the .357 magnum: taking the size to the nearest 1/1000th.

[Buenchico]

Metrication came to this country slowly. Before we started to commonly use metres and centimetres, engineers 'decimalised' the inch. So, instead of having measurements such as 5 and 11/16 of an inch (which is a b**ger to type!) , decimals were used. e.g. 5.00", 5.05", 5.10", etc. Of course, the actual measurement required in an engineer's scale drawing might be something like 5.03" but marking hundredths of an inch on a rule is impractical, so twentieths were used instead.

[Prudie]

Military guns are now measured in millimetres, being the diameter of the barrel.

[MTbowels]

alavahalf, I referred to it as an engineer's steel rule but in reality it's only a figure of speech. It was in fact a common or garden steel rule bought in WH Smith manufactured by those well-known ruler manufacturers, Helix. Just visit your nearest WH Smith and you can buy one too!

The reason I referred to it it as an engineer's steel rule was to distinguish it from those plastic rulers that come to mind when one thinks of rulers.

I agree with carrust and have never heard of a rule with 1/20th of an inch graduations.

[beso]

1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, 1/256. Basically it is binary system.

Gets a bit messy even saying it, eg. "one and 231/256 ths". At the precision end, a decimal system becomes more sensible. The 1/20 is just the big end the decimal system.

I have a vernier caliper marked in the binary system as well as thou.

[alavahalf]

I thought this one had passed under the bridge but I suppose I will have to answer.
MTb .. initialy you haven't got ..''"completeness"? and now you say it was only a figure of speech. We are either being factual or we are not.

I have just been down stairs to my tool cabinet and the first ruler I pull out is a Rabone Chesterman No. 64 ...
... on one edge it has 10ths 20ths 50ths and 100ths all of these were used when I was in engineering.
I have only pointed out, how close you were to the answer ...
with your initial question.... even though it was only a figure of speech.

[stuey]

Alavahalf, as a matter of interest, I'm pretty sure that that is the name on the rule that I mentioned previously. I was going to post a photo to show MTb, but I can't remember where it is:) I also have a spirit-level with a groove in its base for lathe work made by the same company.

[MTbowels]

Clearly if this post has demonstrated anything, it is that the 1/20th scale is obsolete and has no place is modern engineering metrology.

It was not an issue of being factual or not: I clarified the source of the ruler to illustrate that this type of rule, commonplace in engineering workshops throughout the land, is available not only from engineering suppliers but from retailers that one would hardly give first consideration when a buyer required one. No doubt such a retailer would be the first port of call for an artist etc.

Years ago, steel rules of this nature were only available from engineering suppliers. Hence "an engineer's rule".

[tamborine]

Stop bragging

[alavahalf]

stuey ...at the time Rabone Chesterman were the benchmark ...
they made the best tools around and you wouldn't be seen with anything less in the inspection department .
They are now collectable and believe it or not their 6'' rulers change hands for £10.00 -15 on ebay.
That was equal to 2 weeks wages when I became an apprentice... (should have bought more rulers !)

..... the ones with the 10th scale being slightly more valuable... I shouldn't really be telling you this.

[stuey]

Alavahalf, I guess you'll know what I mean when I say that I have a collection of my father's "go/no-go" gauges.

[Barks]

And this would be two pages answering the question "what's easier to use, millimeters or inches"

And to pick up on Peter Pedant's comment about micrometres (0.001mm or 1mu m) as opposed to micrometers (the measument tool or precision G-clamp) I regularly measure down to

[alavahalf]

Like I said ... the answer was in the initial question.