SAE to metric conversion?

[r75boxer]

math.jpg

[Tony the Skin]

Look out for inflation with time

[windmill john]

Dime a dozen these pictures

[barryh]

I have a set of imperial open ended spanners given to me when i was an apprentice. It seemed a little sacrilegious to do it after 50 years but I've ground some of the bigger ones out to metric for use on plumbing fittings. At least now they get used.

[Mjolinor]

I have a set of imperial open ended spanners given to me when i was an apprentice. It seemed a little sacrilegious to do it after 50 years but I've ground some of the bigger ones out to metric for use on plumbing fittings. At least now they get used.

You will regret it. :)
We should not kowtow to the French!

[windmill john]

Best thing that happened to spanners etc... metric.

I’ve got some AF and some Whitworth, as well as metric of course.

I know, relating to the AF and Whitworth, one is head size and the other, Martian weather measuring equipment, but they are a pain in the armature.

I take a selection to my Enfield and then just pray.

[Mjolinor]

Best thing that happened to spanners etc... metric.

I’ve got some AF and some Whitworth, as well as metric of course.

I know, relating to the AF and Whitworth, one is head size and the other, Martian weather measuring equipment, but they are a pain in the armature.

I take a selection to my Enfield and then just pray.

Really?

The metric system is ludicrous all the way round. There is no logic to it whatsoever and no gut feeling is possible.

[windmill john]

Please... explain to me how it is ludicrous!

[Mjolinor]

OK. tell me when to stop.

It is not sensible to have a measuring system that covers everything. It is far more sensible to have a system for each range. In the Imperial system this is things like inch, yard, fathom, chain, furlong and mile.

Making a shelf that is, for example, 1.5 10 millionth of the distance from the North pole to the equator long must shirley be a joke one would think but no, that is exactly what is was defined as.

Using a base 10 for any system is hard and illogical, it is about the worst even number you can have for a base. The imperial system uses sensible numbers like 12 or 16 both of which are much much easier to work with. You even used to buy eggs in sixes or dozens, not so much now, they come in 10s. :)

When it comes to small measurements then the Imperial system actually switches to binary which is really easy. You get things like 1/16. 1/8, 29/32. Each level of precision is a multiply by two and involves only binary increases thereafter.

Never in the history of mankind has an error in manufacturing resulted in a times 10 error. This only happens with the metric system and it happens a lot.

Do you want more or will that do?

[keiththeoutfitter1]

Metric’s ok by me.
When I was nobbut a lad, I had a Saturday job in a carpet shop. Customers would come in and say they had a room 19’7” x 13’2” and they liked that lino (it was a long, long, time ago) which was, say£2 7s and 5d a square yard and how much would it cost. Just to complicate things, a lot of the lino came from Europe and was 2m wide.
No calculators then either.

[windmill john]

You might be right, I haven’t the intellect to argue. When it comes to mechanics, it’s always been easier (for me) to work on Japanese and European bikes when choosing spanners.

Maybe starting mechanicing in 1977 and my first bike being a Yamaha......

I’ll be honest, when quoting small measurements, 0.0002 of an inch, I just blink and reach for the metric equivalent.

Keith, I worked for Marley’s years ago and you’re right, Lino 2 metres wide sold by the foot.

[peter]

We did have those things over here, a "duim" = circumference of a thumb, an "el" from the point of the little finger to the elbow, a "span" = distance between the end of a little finger and the end of a thumb from a stretched hand. The size depends on the person doing the measurements.
We also had a "pond" = half a kilo, a "ons" = 100gram , also a "bunder" or "are" to describe the size of a patch of land.
They're all gone now, it's a long time since the introduction of the SI-system although things like mmHg still being used.
But we could go to the most simple system there is. It only has one's and zero's... The binairy system.
It's so simple even computers can use it.

[barryh]

I’ll be honest, when quoting small measurements, 0.0002 of an inch, I just blink and reach for the metric equivalent.

I'm the opposite. If I see a valve clearance in metric it means nothing to me. My brain goes:

1mm equals 40 thou so .1mm equals 4 thou etc until I've converted it something I can grasp.


I blame school 55 years ago where we did metalwork in metric and in the room next door, woodwork in imperial.

[Mjolinor]

I’ll be honest, when quoting small measurements, 0.0002 of an inch, I just blink and reach for the metric equivalent.

I'm the opposite. If I see a valve clearance in metric it means nothing to me. My brain goes:

1mm equals 40 thou so .1mm equals 4 thou etc until I've converted it something I can grasp.


I blame school 55 years ago where we did metalwork in metric and in the room next door, woodwork in imperial.

Why blame anyone, you have the grasp of it all and that is way better than any of the alternatives.

[wulfrun]

OK. tell me when to stop.

It is not sensible to have a measuring system that covers everything. It is far more sensible to have a system for each range. In the Imperial system this is things like inch, yard, fathom, chain, furlong and mile.

So the centimetre, millimetre, decametre, kilometre etc are basically pointless? Conveniently, they're all multiples/divisions of 10, which only involves moving a decimal point. As opposed to multiplying by 12, 3, 8, 1760 or whatever the conversion may be.

Making a shelf that is, for example, 1.5 10 millionth of the distance from the North pole to the equator long must shirley be a joke one would think but no, that is exactly what is was defined as.

Whereas making a shelf that's 3 times the length of a certain individual's physical attributes is? At least the Earth's dimensions are reasonably stable.

Using a base 10 for any system is hard and illogical, it is about the worst even number you can have for a base. The imperial system uses sensible numbers like 12 or 16 both of which are much much easier to work with. You even used to buy eggs in sixes or dozens, not so much now, they come in 10s. :)

Few people struggle to move a decimal point, whereas an awful lot struggle with the mathematics of fractions.

When it comes to small measurements then the Imperial system actually switches to binary which is really easy. You get things like 1/16. 1/8, 29/32. Each level of precision is a multiply by two and involves only binary increases thereafter.
Do you want more or will that do?

Binary is a very alien concept to most people and not easy to make sense of, even those with a computing background. You can hardly see 29/32 as binary, even though I accept that it is. I don't see users of imperial systems (mostly the US) converting their measurements to binary, doing binary addition and subtraction (or worse, multiplication) and then back to a fraction.

I'll stick with metric thanks!

[Mjolinor]

OK. tell me when to stop.

It is not sensible to have a measuring system that covers everything. It is far more sensible to have a system for each range. In the Imperial system this is things like inch, yard, fathom, chain, furlong and mile.

So the centimetre, millimetre, decametre, kilometre etc are basically pointless? Conveniently, they're all multiples/divisions of 10, which only involves moving a decimal point. As opposed to multiplying by 12, 3, 8, 1760 or whatever the conversion may be.

Making a shelf that is, for example, 1.5 10 millionth of the distance from the North pole to the equator long must shirley be a joke one would think but no, that is exactly what is was defined as.

Whereas making a shelf that's 3 times the length of a certain individual's physical attributes is? At least the Earth's dimensions are reasonably stable.

Using a base 10 for any system is hard and illogical, it is about the worst even number you can have for a base. The imperial system uses sensible numbers like 12 or 16 both of which are much much easier to work with. You even used to buy eggs in sixes or dozens, not so much now, they come in 10s. :)

Few people struggle to move a decimal point, whereas an awful lot struggle with the mathematics of fractions.

When it comes to small measurements then the Imperial system actually switches to binary which is really easy. You get things like 1/16. 1/8, 29/32. Each level of precision is a multiply by two and involves only binary increases thereafter.
Do you want more or will that do?

Binary is a very alien concept to most people and not easy to make sense of, even those with a computing background. You can hardly see 29/32 as binary, even though I accept that it is. I don't see users of imperial systems (mostly the US) converting their measurements to binary, doing binary addition and subtraction (or worse, multiplication) and then back to a fraction.

I'll stick with metric thanks!

As expected, there are the reasons that most people consider metric as sensible. :roflmao:

[r75boxer]

When I posted the image I had no idea it would result in such a lively discussion. Thanks to all for your contributions.

Merry Christmas and all the best for the new year!

Kevin

[wulfrun]

As expected, there are the reasons that most people consider metric as sensible. :roflmao:

I also forgot to mention: the nautical mile is based on? Oh yes, an angle-derived fraction of the Earth's equatorial circumference.

[Mjolinor]

As expected, there are the reasons that most people consider metric as sensible. :roflmao:

I also forgot to mention: the nautical mile is based on? Oh yes, an angle-derived fraction of the Earth's equatorial circumference.

Which is as sensible as it can be considering what it is used for. Much the same as all the other Imperial units.

[peter]

Even people within the metric system live in different worlds.
Where some write measurements down in meters others do in cm, mm or even smaller, depending on the field you work in.
I'll stick with mm with an accuracy of 0.1mm.
For you who want to live with wierd measurements, try measuring your speed in Ångström/week

[Mjolinor]

Well that would be pretty daft. That is why there is an Imperial measurement system in the same ballpark as the things that need measuring, unlike the Metric system.

[windmill john]

Well, off to bed soon. I hope Santa has left something special at the 30 centimetres of my bed

[george baker]

Hi
Centimetres are not SI

Last week a14 yo introduced me to dm3 in his homework, I had to convert it to cubic metres (200 gallons) divided by 1000 to realise his teacher meant a litre- again not SI

Don't get me started on tpi and the illogically or otherwise of 1 & 1.5 mm thread pitch for every metric thead

Merry Christmas

G

[Mjolinor]

Don't get me started on tpi and the illogically or otherwise of 1 & 1.5 mm thread pitch for every metric thread

Merry Christmas

G

and that is the simplified version. :)

[Mjolinor]

Not all of the ludicrous measurements that the French tried to introduce caught on. The ten hour clock fell flat on it's face and the idea that angles should be measured in 100th of a right angle was poorly accepted though it is still used in some places.

I suppose on first looking the 400 per rev and 360 per rev do not seem much different, both pretty damned random but the 360 per rev ( from the Babylonian counting system chosen to maximise divisors) allows the Earths rotation to be used directly so that you can know roughly where you are by observing the sun at a particular time (noon). That, of course, is where the nautical mile comes in, 60 nautical miles being one degree of rotation at the Equator so if you know your latitude you can easily work out how far you have gone in any 24 hours period provided the sun is visible. It is a good way of measuring angle for that particular use but fails or is more difficult when you are dealing with things that are not related to travel on the surface of the planet. That is where radians come in. However you do it it is not possible to get away from the sum of an infinite series but at least the sum needed for angles and circles is known well enough as Pi (3.141 etc etc)