Metric vs Imperial – Practical or Traditional?

[Nicholas FarrParticipant @nicholasfarr14254]

Hi,
    Posted by Paul Trotter on 06/11/2010 01:15:33 At the end of the day there is no right or wrong answer, it is purely a question of personal choice.>>

 

Exactly what others and myself have been saying. Whichever unit of measurement you use, you can make identical parts. (unless you pretend one or the other doesn’t exists or is US)

 

Regards Nick.

[blowlampParticipant @blowlamp]

I had to smile when I read the post above by ady, which says “…If you got it wrong then your eyes were gouged out…”
and is followed by paul trotter’s comment of “Sorry I don’t see the problem…”
 

 

Martin.

[Paul HansonParticipant @paulhanson23918]

This thread is interesting – the debate seems to go which is better for one person or another and historical facts, knowledge about wierd units etc

 

I think we are missing an important point – what does it look like for a newcomer coming into the hobby? I am a newbie and I have to admit it all looked pretty daunting and off putting (do I buy a metric or imperial machines or drills bits etc).

 

It’s all straight forward for the experts – it looks less wonderful for new recruits (who increasingly will be metric oriented only)

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Paul, you buy whichever machine you feel comfortable with. There is nothing wrong with going all metric. All engineering is a compromise against cost, therefore if you have plans with imperial threads for instance, you can sustitute them for metric ones. Its really only basic arithmatic.

 

Regards Nick.

[blowlampParticipant @blowlamp]

I haven’t read the whole of this thread, but I think we all need to get DRO’s or this discussion will never end.

 

Martin.

[KWILParticipant @kwil]

I have DROs on all machines but it does not stop you choosing whatever suits you.

[chris stephensParticipant @chrisstephens63393]

Hi Paul,

This was going to be my last post on the subject and it was going to say “I give up”.

 

Instead I shall try to offer some advice. If you are starting in this hobby of ours, the first machine you need will be a lathe. If you buy new, get a metric one and ask them to throw in a calculator. If buying pre-owned, get the best you can afford and hang the units its calibrated in. Note here that some lathes have proper dual marked hand wheels, like my Colchester Bantam. I doubt you will be buying a new Myford, so this anomaly wont interfere, but their Metric lathe has an Imp(tpi) gearbox????

 

Now some advice on things like drills, buy metric. A set of 1-5.9 and 6-10 , in 0.1mm increments, will cover most threading and reaming requirements, to which you can add drills going up by 0.5mm as needed. Metric drills are much more sensibly marked than either “number” or “letter” drills. Other cutting tools will be metric these days, so go with the flow.

 

You are entering and interesting and fulfilling pastime, and you should realize that all it takes to convert from one system of measurement to the other is merely the matter of pressing a few buttons on a calculator. There may be some who say you should not have to do this and if everything was to the same measurement standard you would not have to. Well where’s the fun/challenge in that?

 

 To summarize, if new buy metric, if used get the best you can afford. 

 

 chriStephens

[Ian AbbottParticipant @ianabbott31222]

Sorry, I didn’t double check the calculator.

 

The theatre is in fact 225 feet outside measurement, the ridiculous millimetre figure on the plan should have been 68580 mm.

 

Lesson, don’t type messages when someone else is trying to clear the table 

 

Ian 

[Ian AbbottParticipant @ianabbott31222]

While I was sending the last message, the boss, who is completely Imperial illiterate, said, “Oh, that’s easy, all you do is move the decimal point two places, or should that be three places, no one place, yes two, I think.”

 

Ian 

[Chris TriceParticipant @christrice43267]

The only points I’ve repeatedly made are:

 

That metric as a system is scientifically logical being cross linked with other forms of measure such as weights and densities, where Imperial is a system based on unscientific arbitrary human whim and nothing else.

 

People can use whatever system they prefer… Most can work in both and that’s cool.

 

…. but the imperials who refuse to see metric and deny it are eventually going to drown in the incoming tide (or at least get their feet wet…).

 

No one is being told to convert to metric now! They’re simply being alerted that the metric tide is inevitably on its way in and the imperial sandbank they’re standing on is eventually going to get  swamped and submerged. They can climb aboard the metric raft at any time or simply stand their ground trying to keep their imperial heads above water because they like the feel of imperial sand beneath their feet (feet, get it?). How long the tide will take is up for debate but it will still arrive.

 

Here’s an interesting thought. Any imperial measurement of any kind (inches, thou’s fractions, feet) can be expressed in the same metric language, millimetres, however try to express 7.5mm (a random example plucked from the air) in imperial measures using anything other than decimal subdivisions of inches. The calculation is mind mangling unless you use a single multiplication factor to “scale up” millimetres to thou’s. Anyone want to throw in an exact fraction of an inch without rounding to the nearest 64th” (a large step in precision engineering terms)? If nothing else, it illustrates the complexity of anything other than a decimal system in which case 10″ should equal a foot and 10′ equal a yard. 

 

 

 

 

Edited By Chris Trice on 06/11/2010 17:19:21 typo’s

Edited By Chris Trice on 06/11/2010 17:21:30

[VersabossParticipant @versaboss]

Sorry gents, I cannot help laughing a hole into my belly, as we use to say here.. The least I would expect from you ‘imperialists’ would be not to make such silly mistakes, which invariably are excused as ‘oh, that was just a typo’ or as ‘ sorry, did misread the calculator’.

Jan, 5715 mm is not  the same as 225 ft; ok we had this one.

Terryd, if I see on a plan something written as 118″ – 9″, how long would I cut a string or whatever? An easy one for a 10 years old; well 118 minus 9 is 109 inches, isn’t it?

Crashing into Mars, as Ady rightfully remarked…

Going in Chris’ footsteps, my last contribution also. Except maybe when even more silly mistakes have to bemoaned.

Greetings, Hansrudolf

[Sub MandrelParticipant @submandrel]

Chris

 

Can you explain the scientific logic behind the hectare?

 

 

 

Neil

[chris stephensParticipant @chrisstephens63393]

Hi Chris,

While I agree with you about no compulsion to change, you might be putting some peoples back up by the way you imply they are stick-in-the-mud, make that sand. People can use Imp units for as long as there are measuring instruments that can read in those units. I am sure that there would be some people still using cubits or whatever if you could still buy rulers at B&Q marked in those units. I don’t see the scale train people changing their name to metric any time soon.

 

Re your last Para, I think you are forgetting that nobody who uses a micrometer works in fractions. IMP can be in either expressed as fractions or decimal as you can with metres, 1/2metre is just a valid as 0.5metre. So your thought falls down a bit,  7.5mm does not have to be put into a fraction of an inch, as it can justifiably be put in decimal, 7.5/25.4=0.295″ not a “standard” figure I grant you but hardly mind mangling conversion. It must be remembered that All units of length are arbitrary as there are no accurately measurable natural constants for length, even in the metric system. Even when using light waves to measure something the wave length first had to be defined as a distance. There are physical constants involved for things like temperature, boiling or freezing of water etc but weight and length, no.

If the Earth were a perfect sphere you could perhaps use 1/10,000,000th of the equator to the north pole distance, but it isn’t and so even here some element of averaging and theoretical calculation is needed. As for light travelling so far in a vacuum in 1/299,792,458 of a second, hardly an easy number to use. Even a second is now a theoretical one, as the sixtieth of a sixtieth of a twenty-fourth of a day is variable by modern measurement capabilities. You can’t define a Metre except by calculation. I don’t suppose you are volunteering to walk from the equator to the north pole with a steel tape are you? Whereas three barley corns, or whatever an inch was defined by, are a physical , not a theoretical, unit that was fairly universal and on a “human understanding” scale. Yes, Yes, I know it is not up to engineering precision as it stands, but it worked OK as a starting point. Once you have set your arbitrary value for a metre then distance and weight are easy and dare I say it logical, but a metre is a hypothetical unit first and foremost, despite what some would say. 

Please take the above in a the spirit it was intended ie not too seriously, just a bit of fun as a diversion from tonight’s fireworks.

 

Can our nice new bit of Eye Candy , sorry web editor, put a time limit on this topic so we can think of a new excuse for poking fun at each other. I do so hope she has a sense of humour or my posts might never see the light of day again, OK let me say it before you lot do, Yippee and thank heavens for small mercies.

chriStephens 

PS Just had a thought, which is more honest a standard based on a few bits of vegetation or  a standard based on a falsehood? That is a rhetorical question I’m not expecting or wanting to start another round of posts. Now, unless seriously provoked, I shall shut up on the subject. I feel a circular argument naturally goes nowhere, and must therefore be pointless.

 

 

 

[Ian AbbottParticipant @ianabbott31222]

You have to understand here Hansrudolph, that I am incapable of grasping the figures on any readout, metric, Imperial or fraction, correctly.

 

DRO’s  in my hands are a deadly weapon and I started using a magnifying glass to read a vernier thirty years ago to narrow down the available numbers to the few inside the lens.  Not that my eyesight is bad, it’s just the connection with my brain which can’t accept any measurement with numbers in the tens of thousands.  At least an inch generally limits the options to a thou. or two.  Decimal points are optional with me and in the time it takes to scroll the screen back to the line I’m writing, the figure that I’ve just read had disappeared into the ether.

 

Given the potential for catastrophe  when placing the decimal point  in a number such as 68580 compared to fifty feet plus 25 thou. I’ll take the inch any time.

 

And yes, of course I use metric constantly alongside imperial and “this long”, I just don’t find it has the same warm feeling as a nice comfortable 1/64″, three chains or a furlong.

 

 

Ian 

[Ian AbbottParticipant @ianabbott31222]

And,  I did enjoy putting a sign up saying “1/3 of a kilometer” pointing to our business.

 

(Which was in engineering, fortunately I gave that up in 1983)

 

Ian 

 

[Chris TriceParticipant @christrice43267]

Posted by Stub Mandrel on 06/11/2010 20:15:21:

Chris

 

Can you explain the scientific logic behind the hectare?

 

 

 

Neil

In all honesty, no. 

[dcostaParticipant @dcosta]

Hello.

 

The hectare has the same purpose as the acre which is to measure areas.

See, please, http://en.wikipedia.org/wiki/Hectare.

Dias Costa

Edited By Dias Costa on 07/11/2010 01:16:03

[Chris TriceParticipant @christrice43267]

Posted by chris stephens on 06/11/2010 20:18:49:

Hi Chris,

While I agree with you about no compulsion to change, you might be putting some peoples back up by the way you imply they are stick-in-the-mud, make that sand.

 

“SNIP”

 

PS Just had a thought, which is more honest a standard based on a few bits of vegetation or  a standard based on a falsehood? That is a rhetorical question I’m not expecting or wanting to start another round of posts. Now, unless seriously provoked, I shall shut up on the subject. I feel a circular argument naturally goes nowhere, and must therefore be pointless.

 

 

 

No offence taken or intended. Just to be clear, I’ve said earlier that I use imperial so I’m potentially tarring myself as a stick in the mud except I also work in metric and can see that fundamentally, looking at it without the familiarity/comfort filter in place, it is a more rational and easier to use system. For that reason, it will inherit the Earth and Imperial will wither and die. As you say, people will continue to use it for as long as tools and machinery include it but there will come a time when the machinery manufacturers ask themselves why they’re bothering to include imperial measures for the ever dwindling percentage of customers that will use them. You can’t work in imperial if you have no means to measure your output. It’s more than likely that imperial will continue until this generation have curled up their toes so no reason why anyone here today shouldn’t use imperial but there will come a time when an inch will be as meaningful to a young engineer starting out as a groat is to a young banker today and like the groat, imperial will be remembered purely as a currency people used to use. I’m not campaining or trying to convert anyone. I’m just saying I use both and one is clearly easier to use if you start from basics. It was touched upon earlier that those who like imperial do so because it’s familiar and it’s what they know but that’s not a reason to resist a change that makes logical sense. I suppose in that respect, imperialists are by definition stick in the muds but the difference is that the rest of the world doesn’t care since they can’t alter the fact that metric is coming. I’m sorry if anyone finds it uncomfortable or threatening. I’m just stating what seems obvious. 

Edited By Chris Trice on 07/11/2010 01:30:56

[Sub MandrelParticipant @submandrel]

Hi Dias

 

> The hectare has the same purpose as the acre which is to measure areas.

> See, please, http://en.wikipedia.org/wiki/Hectare.

I live and breathe hectares in my day job – its about the size of a football pitch

 

But 1 hectare = 10,000m2 or 0.01 km2.

 

Logically we should use the are as a unit of area, 1000 square metres but (a) it’s a bit too small, only a tennis court (and tennis is a silly game), and  (b) it would be a square  with sides a bit longer than 31.6m long – all far to awkward for estate agents, unlike sensible acres a furlong long by a chain wide.

 

Now the hectare is exactly 1 olympic sprint long on each side, which is sensible, but it just dosen’t fit with nice ten-to-the-power-of-three metric, so much so that it (and the are) have been cast out of the metric fold and really have no more legitimacy than good, sold acres.

 

Neil

[TerrydParticipant @terryd72465]

Posted by Stub Mandrel on 11/11/2010 22:06:55:

Hi Dias

 

…………..

Logically we should use the are as a unit of area, 1000 square metres but (a) it’s a bit too small, only a tennis court (and tennis is a silly game), and  (b) it would be a square  with sides a bit longer than 31.6m long – all far to awkward for estate agents, unlike sensible acres a furlong long by a chain wide……………

 

Neil,

 

 Out of interest, It is thought that a furlong was the length of a furrow (220 yards) which could be ploughed by a team of 2 oxen without stopping and the rod (4 to a chain) is thought to have been the length of an ox goad.  Hence it was easy to measure the acre with implements and animals at hand.  How accurate that was is a matter of conjecture.  The modern international acre is defined as 4840 sq yards – unfortunately worldwide there are different definitions of the yard.

 

Now that surveyors use lasers and sonar devices, how easy is it to get an actual surveyors chain.  The only applications I know of is measuring a cricket pitch and the radii of railway curves.  Any other suggestions?

 

 

Terry

Edited By Terryd on 12/11/2010 10:49:45

[Sub MandrelParticipant @submandrel]

A dumpy level?

 

Great fun to be had by all!

 

Actually a dumpy level would be a good project for ME and ideal for laying out railways or anything with a limited vertical component..

 

Neil

[Chris TriceParticipant @christrice43267]

Market forces always have the last say. When demand becomes too small to justify filling the imperial niche, it will wither away. While there’s money in it, imperial will survive. As soon as imperial stuff starts sitting on shelves unsold, it’ll be quietly discontinued. That’s already happening with many suppliers. They’re motivation is not about keeping imperial alive. They’re only interest is in what products turnover in a reasonable time.

[Ian S CParticipant @iansc]

Chris, they’v got me going metric on such as bearings, imperial ones are about twice the price of metric, have’nt compaired nuts and bolts.  Ian S C

[VersabossParticipant @versaboss]

Posted by Stub Mandrel on 11/11/2010 22:06:55:

Logically we should use the are as a unit of area, 1000 square metres but (a) it’s a bit too small, only a tennis court (and tennis is a silly game), and  (b) it would be a square  with sides a bit longer than 31.6m long – all far to awkward for estate agents, unlike sensible acres a furlong long by a chain wide.

  

 

Oh my, I thought I will restrain from further answers here, but it starts to make me angry reading stuff from people who don’t even know simple arithmetic.

Yes, the are is an area unit, but it is 100 sqm (10 by 10) and not 1000. 1 HECTare is, as the name says, 100 ares!!! And 100 times 100 gives 10000, as I learned in Miss Nicolet’s class about 60 years ago.

Sorry for that rant. But if you want to honestly discuss something, then first get your numbers right and check thrice what you write. (Well I just do…)

Greetings from a somewhat angry Hansrudolf (now disappearing into the workshop)

[James fortinParticipant @jamesfortin46829]

i often use metric as it is easier to work in 10s but find it ironic that after trying to standardise all the witworth threads and then making a new standard of metric thread, engineers still have to use imperial threads for specialised parts or mechanics which require a non standard thread. i prefer to use inches when do ing diy as it is a smaller number i.e. 2540mm or 100inches.

 

 

no doubt a new thread standardisation will be invented in 50 years or so and then the model engineers will be calling metric ‘old’ and ‘traditional’  

Edited By James fortin on 01/12/2010 09:32:39

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