An interesting co-incidence of units

Just let me check my 0 - 1 Ell micrometer................................................

Depends how many infinities you think there are pgk pgk?

Martin

The whole Imperial/Metric 'thing' is an oddly personal thing I find and I'm sure we all have our ways of moving between the two.

Being brought up on Imperial - I generally tend to visualise things that way. I "know" what an inch, a foot and a yard "look" like. I used to run the 100 yards and I still walk (and drive) in miles. But I also have a few simple conversions that I can do in my head. An inch is 25.4mm (so 2" is 50mm) and a metre is 39" (all near enough). I also know that there are 30 miles in 50 kilometres (again near enough). All easy - but thinking about this post - I realised I couldn't (immediately) say how many mm in a foot (it's 304.8 - but lets say 305!) and that I probably prefer to just remember that 10" is 254mm.

In my workshop practice, I'm still not exactly settled on either system. Most of my machines are old iron and have imperial dials, so I tend to machine (and think) in 'thous' but oddly when using CAD or measuring longer work/material lengths - I use mm. (am I alone in disliking cm?). It's partly because I've never been very 'fluent' in fractional measurements (although I know a guy who can add a list of fractional units at a glance). I do have a rule with 'decimal' inches on one scale but most of my rules just show either fractional inches or mm - and mm scales do seem easier to read.

I'm sure there are lots of folk reading this that just use one or the other system and it's not really a problem in practice... but for anyone 'new' out there who finds themselves in a 'mixed' metrology world there are two things that will really help. The first is knowing that 1mm = 40 thou (near enough) (or 4 thou = 0.1mm) and the second is having an A4 sheet handy in the workshop that lists the decimal 'inch' and 'mm' conversions of their fractional equivalents in 1/64th inch steps up to 1" (a simple spreadsheet will provide the data).

Anyway - if Michael wants to play with his numbers and find interesting 'intersections' then good luck to him.

Perhaps also - when I next need to convert 1.25" to mm, I might even remember that it's 31.75mm without having to reach for my calculator...

Regards,

IanT

Give them an inch and they'll take 1.609 km.

Neil

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Neil,

I only continued to post because no action had yet been taken to delete the thread, and in the meantime a couple of non-confrontational posts had been made; to which it seemed only poilte to respond.

On balance, however ... I really wish I hadn't started it.

MichaelG.

My Granddaughter used to count: One, two, three, lots..

As to specifically how many infinities then I suppose one starts by counting how many sets of parallel lines meet each other.

I will put my head above the parapet & say that I am with Michael on this one! Of the tools that I inherited from my Dad, probably the most prized one is a Rabone Chesterman 5 inch/127mm rule. It does not measure any better or worse than any other: it just has a "symmetry" that I find interesting.

Dr Dave ... Thank You

Am I correct in thinking that's the No.33

Just found an ebay advert for a batch of New Old Stock

16 listed, and all 16 sold

MichaelG.

That be the one. And, no, you can't have mine!

Funnily enough I too have a Rabone Chesterman No33 conversion rule, it has mm to 1/32" on one side and mm to 1/20" on the other, an interesting item but I don't use it everyday, I also have a Shardlow metric and imperial mic, not the easiest thing to use, I bought it as a curiosity. There is an advert for the No33 on eBay £2.99 and 99p post at this minute.

Mike

Edited By Mike Poole on 30/01/2017 21:13:51

Edited By Mike Poole on 30/01/2017 21:15:49

This is my favorite rule.

I cannot get on with the 1/2mm divisions as they clutter the rule up too much and you can easily split a division by eye if you don't have the clutter.

I also like the same scale top and bottom as sometimes you are taking a measurement from the top of a part and other times from the bottom all all too often to save real estate they will give you a different scale when all you want is to work how you want to.

This increasing - decreasing division layout was devised by M&W as being the most pleasing and easy to read.

The problem is with wanting a M&R layout, same scales top and bottom and no 1/2millimeters is that no one makes one so I had to laser engrave my own.

.

Thanks, Mike ... That's the same seller as I mentioned earlier

... He must have found another box of them !!

MichaelG.

Let me guess....

Most of those who posted are retires and have WAY too much time on their hands.

In ordinary mathematics there are two infinities - countable and uncountable.

Andrew

I've wanted a rule like that sine I saw them described in New Scientist when I was a teenager! I think actually the layout was designed at NPL for easy reading, but never really became popular.

.

The aforemebtioned Rabone No.33 uses that layout for the millimetre scale.

"though of course it loses the 'same both edge' feature favoued by JS.

https://goo.gl/images/VcsnQy **LINK**

MichaelG.

pgk pgk

|My Granddaughter used to count: One, two, three, lots..

As to specifically how many infinities then I suppose one starts by counting how many sets of parallel lines meet each other.|

Consider the infinite series the sum of all the integers and the infinite series the sum of all the even integers. The even integer series can be obtained by multiplying the integer series by 2 so now we have two definitions of infinity one of which is twice the other.

:0)

Martin

Yes, I find that too. Could it be an age thing? No point bothering as we cannot change that?
So often the other side of the rule is left blank - what a waste!

Having recently mentally binned cms and now exclusively using mm I find I make less mistakes in metric.

In the process I binned the rules which did not comply. The new ones are Rabone and I find them really good. They are metric one side and imperial the other, which suits me - some might want both on one side to compare but I just measure twice if needs be. The metric side is all mm, one edge in 1mm steps, the other in 0.5mm steps. There is plenty of cheap tat around at 90% less than Rabone but I, at least, can see the difference and the format works for me.

Just me. Thank you Michael G for starting this off - you got some stick but I found it interesting.

I,ll second Clives remarks re Micheal G. Well done Micheal keep them coming, allways interesting

Thanks Roy

Juggling 2' and 3' rules today, I think they should read left to right on one side and right to left on the other.

Neil