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Digital readings

Have i got this correct

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Steviegtr21/10/2020 23:59:29
2150 forum posts
303 photos

Can it be please verified that i have these figures correct or not. It is my DTI or dial gauge readout & in old age i get a bit confused with all the zero's.

dti .jpg

gerry madden22/10/2020 00:25:17
187 forum posts
83 photos

Yep all correct !

Bill Phinn22/10/2020 00:33:01
534 forum posts
82 photos

It looks right, Steve.

I don't think anything better demonstrates the objective superiority of the metric system than the fact that, in order to be functional, the imperial system is, most of the time, a metric system too.

Steviegtr22/10/2020 01:30:04
2150 forum posts
303 photos
Posted by Bill Phinn on 22/10/2020 00:33:01:

It looks right, Steve.

I don't think anything better demonstrates the objective superiority of the metric system than the fact that, in order to be functional, the imperial system is, most of the time, a metric system too.

yes Thanks


David Davies 822/10/2020 07:17:04
146 forum posts
9 photos

Surely this is an instance of the imperial system being used in decimal mode not in a metric mode?

Nicholas Farr22/10/2020 08:59:26
2878 forum posts
1295 photos

Hi David, a decimal is not restricted to an imperial or metric system, in fact it can be applied to anything as it represents a number that is not a whole number, i.e. 1/2 of 1 inch is 0.5 inches, 1/2 of 1mm is 0.5mm both of which are both a fraction of a whole and also 50% of a whole, the differences are the actual measuring units used, which can be anything from beans to people etc.

Regards Nick.

Edited By Nicholas Farr on 22/10/2020 09:00:17

Mick B122/10/2020 09:12:51
1941 forum posts
112 photos

The Imperial system for some time seemed to exist in 2 parallel versions - fractions and decimal. The fractional version was always clumsy and inconvenient to use, but encouraged the use of mental arithmetic and memorisation of decimal equivalents. The decimal version is every bit as easy and convenient as Metric, at least at model engineering dimensions - rather less so when you get into yards and furlongs.

And for many of us, the Number and Letter systems will remain irretrievably arcane...cheeky

Maurice Taylor22/10/2020 09:40:17
185 forum posts
30 photos

The only difficulty I have with the metric system is reading a metric micrometer .Does anybody else find it harder than an imperial one?


Clive Foster22/10/2020 10:08:00
2749 forum posts
100 photos
Posted by David Davies 8 on 22/10/2020 07:17:04:

Surely this is an instance of the imperial system being used in decimal mode not in a metric mode?

Indeed. But horses for courses.

The thing about decimal representation is that it matches the decimal number system so its a continuous representation making calculations easy. You just plug the numbers in, do the maths and sort out what it all means afterwards. Scientific folks, like what I was, use the "10 to the power of" scientific notation because it keeps things straight automatically.

But, as Nicholas says, the decimal notation strips the actual measurement unit from the calculation so its easy to loose track of what the numbers mean. Hence the confusion illustrated by steviegtr.

Which can be very dangerous in a more casual situation. Its easily exploited to confuse folk or sell a dishonest conclusion. Objectively most folk can easily visualise the difference between 5, 10, 50 and 100. How about between 10 and 1000. Ummm. OK try 5,000, 5 million and 5 billion. "Well they are all big, the last one is really, really big" is about where most folk check out. Although I'm well able to handle calculation of far, far larger numbers I hit visualisation trouble around the million or so. I've worked with folk who can visualise and truly understand billions. Its rare its hard but the insights can be amazing.

In the imperial system no one is going to confuse an inch with a yard or 1/4" with 19/64 ths. If anyone starts on about 7 miles, 600 yards, 2 ft, 3 and 21/32 nds inches the immediate reaction is "Shaddup Plonker, call it 7 and a third miles." or, more likely about 7 1/2. But I've seen truly serious money, £100 million plus, vanish down a rabbit hole chasing a vehicle mounted system sold fundamentally on a (theoretical) nanometre level ranging ability. Which was meaningless in context.

Folk talk casually about thous and tenths thous but who really appreciates how big they are. OK, OK the 1 thou feeler gauge is the really thin one that breaks almost as soon as you look at it. Now how about tenths thous ...

Sometimes there are reasons for apparently inappropriate units. Aircraft altimeters read feet because the important bit is when they are close to the ground. 50,000 or 50,001 ft matters not at all, 1 ft or 3 ft or 15 ft is important. Little bump, bigger bump or "what did you break this time!".

The aircraft altitude thing is a good example of how folk fail to visualise large numbers. Next you are sat next to Mr or Ms Nervous Flyer and Captain Speaking says "We are flying at a our cruising altitude of 35,000 ft" mutter "Gosh, thats nearly 7 miles up.". Makes Daz and the blue whitener look positively amateur. Folk know what 7 miles is. For me its the distance to the next town over. 35,000 ft is just numbers.


Edited By Clive Foster on 22/10/2020 10:09:31

Edited By Clive Foster on 22/10/2020 10:18:42

Rik Shaw22/10/2020 10:12:39
1433 forum posts
392 photos

Yes Maurice you are not on your own. I was weaned on imperial many years ago and see a clear mental picture in my head of what say .010" looks / feels like. Metric dimensions on the other hand form tangled balls of string between my ears until I reach for my calculator and convert them to imperial.


Nicholas Farr22/10/2020 10:15:15
2878 forum posts
1295 photos

Hi Maurice, if anything, I find metric ones easier, as there are less divisions between each whole number on the barrel to think about.

Regards Nick.

Simon Williams 322/10/2020 10:25:53
601 forum posts
81 photos

I'm with Maurice on this one, though I don't understand why. It can't be just that the width of the space between successive lines on the barrel is narrower - though it is - that's only 5 thou difference. But it is perfectly true that |I find reading a good metric mic' much more difficult than an imperial one. I find myself checking the mic' with digital calipers to see if I read the mic' right!

I even went so far as to modify my little Starrett metric mic' - Micrometer Blues - which has improved it but I still don't find it as intuitive as it should be.

I put it down to old age and dodgy eyesight. If so why is the imperial mic' not equally blurred?

Rgds Simon

Martin Connelly22/10/2020 10:27:36
1797 forum posts
192 photos

I remember when the National Lottery started and the odds of getting the jackpot was around 1 in 14 million. One mathematician said the way to visualise it was to get 14 1m² pieces of graph paper with 1mm gridline spacing. Each 1mm x 1mm square on the paper then represented one lotto result. With odds like that I took the view that the lottery was a tax on the mathematically challenged so never bought a ticket, ever.

Martin C

Peter G. Shaw22/10/2020 11:15:21
1291 forum posts
44 photos

First of all, I was brought up on imperial fractions which I found the very devil to use & understand. To me, subtracting 1/64th from 3/16s was difficult and liable to be wrong.

About 40, or maybe more, years ago, when metric measurements were starting to make serious inroads into everything, I decided that I would build a set of kitchen cabinets using nothing but metric measurements. Furthermore, when I became involved with model engineering, again I deliberately chose solely to work in metric.

Today, in general I think mainly in metric, that is for measurements up to say 1 metre, above that, eg mile, I still use imperial! For some imperial measurements, I now convert to metric first., eg 12 in = 300mm.

There is one advantage with using both systems in that occasionally, I find that a particular measurement might line up with imperial, but not metric, and vice versa. If the actual measurement doesn't matter, say when checking for square using diagonals, then I will happily use which ever system is easiest.

Peter G. Shaw

Steve Neighbour22/10/2020 11:26:32
108 forum posts
1 photos

I was in my 'final' year at senior school when the country decided to change from Imperial to Metric (1973)

Ever since then I continually flip between the two standards and often think of a 1 inch M4 bolt etc. I can not for the life of me fathom distance in metres or kilometres.

Thankfully we still have pints at the pub (when we can safely go to a pub) I dread the day I have to ask for 0.5 litre of my favorite rehydration liquid and always say how my car manages a certain MPG.

My 'new' lathe is metric and I have both metric and imperial micrometers - and love completely confusing my Grandchildren

I guess my generation will eventually pass on, and everyone will then 'think' in metric

Steviegtr22/10/2020 11:50:33
2150 forum posts
303 photos

Yes that was why i posted , Too many 0000 etc. Scrambles my brain. Stupid thing is. I have spent my working life creating & reading drawings in both decimal & imperial. This is the instrument in question . Both imp & metric of the same value.


dti 2.jpg

dti 1.jpg

SillyOldDuffer22/10/2020 12:07:39
7364 forum posts
1620 photos
Posted by Mick B1 on 22/10/2020 09:12:51:

The Imperial system for some time seemed to exist in 2 parallel versions - fractions and decimal. The fractional version was always clumsy and inconvenient to use..

Imperial Measure evolved from a bunch of different systems, all of which I think, depended on fractions. A fluid ounce is ¹⁄₂₀ of a pint, and a pint is ⅛ gallon. A foot is ⅓ of a yard and an inch is ¹⁄₁₂ of a foot. An ounce is ¹⁄₁₆ of a pound, a pound is ¹⁄₁₄ of a stone, and a stone is ¹⁄₂₀ of a ton. There are hundreds of other ratios in the system, and it's not international - USA 'English' measure isn't identical to UK 'Imperial'.

Being well suited to ordinary domestic circumstances Imperial measure is seductive. How far is it to the pub? Bout half a mile, mate. Quarter of hour's walk. Mine's a pint; I'll buy a pie and take half home for the wife. ¹⁄₁₆" is fine for carpentry, and ¼" is fine for tailoring. Superficially all is well.

It's not! Imperial units and fractions seem friendly but become horribly clumsy as soon as advanced sums are attempted. For example, Work is a more difficult concept - it's mass times distance. First issue is Imperial doesn't understand the difference between mass and weight because everything is assumed to be planet Earth, a double edged simplification. Second problem is Work is expressed in two disconnected measures; there's no logical connection between imperial length and imperial weight. Instead there's a huge range of options: work can be measured in Mile-Ounces, Yard-Drams, Inch-Hundredweight and many others.

Look into the detail and Imperial is a mess. Imperial is internally inconsistent, which means calculations are full of unnecessary, confusing and error prone conversions. How many feet per second is 12mph? For advanced use, the Imperial system is a hindrance.

Imperial engineers settled on Foot Tons, Foot Pounds, and Inch Ounces as units of Work, still complicated. After looking at the size of the Imperial muddle, scientists dumped the whole system, eventually developing with the International System of Measure (SI). The SI measure of work is the Joule, which is related to the kilogram, metre and second by factors of one. By design SI minimises conversions.

Although fractions are useful for simple domestic mathematics they are often clumsy and obscure in engineering and science. Mostly much easier to calculate in decimal because the majority of ratios cannot be accurately represented as fractions. Decimals are more general purpose than fractions and can be extended to achieve any required level of accuracy simply by calculating more digits.

Imperial as we know it is a considerable improvement on the original system, but don't be fooled. Metalworkers have long since abandoned ¹⁄₆₄" and ¹⁄₁₂₈" in favour of thou, so we think 'thou' is part of Imperial; not really, Imperial is still full of warts. Despite enormous tidying since Victorian times, Imperial remains far more complicated than SI.

Metric simplifications:

  • Units based on accurately repeatable standards rather than traditional approximations (3 barleycorns to the inch forsooth!)
  • Units chosen, as far as possible, to be related rationally. ( 1W is 1J/s, or 1 kg⋅m2⋅s−3 ) etc. )
  • Decimal throughout. Fractions not normally used.
  • Units scale only in powers of 10, and scale is indicated by standard prefixes. kilometre, kilogram etc.

Of course completely replacing a system of weights and measures is difficult. A 55 year old who's spent his life working in thou is unlikely to see any advantage in metres, joules, and litres! Unfortunately failing to keep up with technology change is a deadly mistake. I suggest British Industry's reluctance to adopt metrication did a lot of damage in the last century, with too many firms and employees clinging desperately to what worked two generations earlier. Their legacy is the worst of both worlds - British engineers today need to understand two systems! A sorry state of affairs if it's due to old dogs refusing to learn new tricks.


IanT22/10/2020 12:17:55
1857 forum posts
180 photos

This subject comes up fairly regularly here and the replies will pretty much depend on your machines and personal preference.

My machines (and I) are all of an age where we are mostly Imperial in nature. But I move freely between metric and imperial measurements without any difficulty at all. I was shaping yesterday and checking the depth of part in the vice with my vernier calliper's 'tail' which (given my eyesight) I tend to read in mm - but if I need a 0.5mm cut then I know that' it's a 20 'thou' down feed. Simples.

But with regards whether Imperial (as shown in the photo) is harder to understand (yes, it probably is) but I never actually "think" in those terms. Personally, I tend to think in 'thous' up to about 100 thou ( e.g. "86 thou" ) and then in inches above that (e.g. 0.375" ). It may well be that I'm a bit strange in this way of thinking but it's what I do. I obviously know that 0.25" is also 250 thou but that's the way I'm wired.

I would probably have to pause before writing down smaller measurement in the way shown in the photo but in practice, I never (ever) do it that way.

BTW - my wife still struggles with the difference between 'mm' and 'cm' . It's my one of my duties to translate the Weather Lady's rain levels into 'inches' for her.



Brian H22/10/2020 12:49:37
2188 forum posts
113 photos

I've worked in a number of firms, mostly in the defence, nuclear and aerospace industries using mostly Imperial but sometimes metric and have never been comfortable with cm's whereas mm is(are) no problem.


Martin Connelly22/10/2020 13:04:48
1797 forum posts
192 photos

Centimetres are not an SI measurement. It is all units and powers of 10 going up and down in threes such as 10³ with one exception, hectares which is a 10 to the power 5 m² area. Centimetres are taught in schools because it is a unit that is believed to suit children.

Martin C

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