discussion A Question of Scale

[Dave Ward]

I have a pre-war machinists reference ( like a Zeus, if any one knows that ) of screw threads - giving all the parameters for machining, ie major diameter, minor diameter, form & pitch - it includes exotica like French bicycle thread, Belgian watchmakers, and about half a dozen Gas threads. It also has the form & size of nuts & screw heads of all sorts - looking at these just makes me happy I only had to learn metric machining! - Although, the final apprentice machining test was to cut a left-hand square thread bolt and nut, using a tool you had to grind yourself! Just given a 25mm dia steel bar & a bit of plate. Mine fitted together, just, after thread chasing & using a pipe extension on the spanner handle!
Dave

 

[boatman]

Matron would be very interested in needle sizes that Jakko has just posted !
Next decusion will be on timber sizes , soft wood v hardwoods.US and English .

Having read all of this thread I'm more confused than normal !

JION the Club John my brain is still in a whirl TOO lol
chrisb

 

[Tim Marlow]

Great stuff Jakko. Just like pure mathematics, of absolutely no use to anybody, but great fun to read. The third paragraph from the end even has number scales 3, 2, 1, 0, 00, 000, etc mentioned. It shows that those that really understood the problem, the engineers Whitworth etc, wanted to go to a scale of thous, but were outvoted by the protectionists who didn’t want the brummies to take over…..as always, vested interests and protectionism ruled over common sense.

 

[Tim Marlow]

Oh, and I’ve just noticed something else…..in most uses of the arbitrary number scale things get smaller as the number decreases, so 1 is smaller than 3, and 00 is smaller than 1 etc. However, on the wire gauge scale 5 is smaller than 1, and 1 is smaller than 00. Utterly bonkers…..

 

[boatman]

Great stuff Jakko. Just like pure mathematics, of absolutely no use to anybody, but great fun to read. The third paragraph from the end even has number scales 3, 2, 1, 0, 00, 000, etc mentioned. It shows that those that really understood the problem, the engineers Whitworth etc, wanted to go to a scale of thous, but were outvoted by the protectionists who didn’t want the brummies to take over…..as always, vested interests and protectionism ruled over common sense.

Oh, and I’ve just noticed something else…..in most uses of the arbitrary number scale things get smaller as the number decreases, so 1 is smaller than 3, and 00 is smaller than 1 etc. However, on the wire gauge scale 5 is smaller than 1, and 1 is smaller than 00. Utterly bonkers…..

OH my brain hurts lol

 

[Tim Marlow]

OH my brain hurts lol

Then my job is done LOL…..

 

[Andy the Sheep]

Have marmite pots a dedicated gauge?
Bewilderedly yours
Andy The Sheep.:tongue-out3:

 

[Tim Marlow]

Have marmite pots a dedicated gauge?
Bewilderedly yours
Andy The Sheep.:tongue-out3:

Don’t know, but I bet the threads on the lid have if you only knew how to look it up…..

 

[Dave Ward]

Advances in knowkledge & especially computers mean most of these are consigned to history -
Similar things that wouldn't mean anything to youngsters - log tables, sine tables, Naperian logarithms, steam tables slide rules, planometers, indicator cards & a lot more esoteric names & kit
Dave

 

[minitnkr]

I happily destroyed my slide rule when I barely passed Materials Testing in college.

 

[Gern]

Back to the SWG for a moment. Given that your wire is supposed to fit in a 1" diameter tube, how about if your wire is 0.6" diameter. Then only one will fit in the tube. But only one will fit if it's 0.999" diameter. There's a big difference between those wires, but does SWG say only one will fit so they are the same gauge?

Duuhhh!

 

[Guest]

Just like pure mathematics, of absolutely no use to anybody, but great fun to read.

If you find mathematics great fun to read, you’re even weirder than me :tongue-out:

Also, XKCD:

as always, vested interests and protectionism ruled over common sense.

And the argument still used by Americans and elderly Brits the world over: “Too difficult, <random mess of units> is much easier (because I know it already)!”

things that wouldn't mean anything to youngsters - log tables, sine tables, Naperian logarithms, steam tables slide rules, planometers, indicator cards & a lot more esoteric names & kit

Not just youngsters (well, depending on your definition of youngster, I suppose …). I was in secondary school in the late 80s to early 90s, and we had none of those — instead, we had a Casio ƒx-82 (Or other scientific calculator of your choice, but my school recommended the ƒx-82.)

Given that your wire is supposed to fit in a 1" diameter tube, how about if your wire is 0.6" diameter. Then only one will fit in the tube. But only one will fit if it's 0.999" diameter. There's a big difference between those wires, but does SWG say only one will fit so they are the same gauge?

I suppose there’s a rule that gauge is the number of wires that will fit tightly in the tube.

 

[dave]

For shotgun gauges; the gauge refers to the weight of a solid ball of lead that might fit perfectly in the bore of a shotgun, expressed as the inverse of said ball’s weight as a fraction of a pound. For example, the sphere of lead that perfectly fills the bore of a 12 gauge shotgun weighs 1/12 of a pound.

 

[Tim Marlow]

Advances in knowkledge & especially computers mean most of these are consigned to history -
Similar things that wouldn't mean anything to youngsters - log tables, sine tables, Naperian logarithms, steam tables slide rules, planometers, indicator cards & a lot more esoteric names & kit
Dave

Used the first four in a couple of jobs, but not for years.

When a population of bacteria is growing without restraint it is known as being in log growth because when the optical density is plotted against time using log paper you get a straight line.

Sine tables are very useful in trigonometry and I can’t really see how you can use a calculator to derive them if you don’t know how they work. Go on then Dave…..what was the nmenonic for remembering them?

Steam tables were an easy way to determine if our fermentation kit was air free when being sterilised. If the temperature and the pressure correlated then there was no air present.

Napier logs are better known as natural logs. Scientific calculators still have that function on them. I know the fx-82 has, I’ve still got mine somwhere. It was the recommended one for the Open University science course. It’s the Log e button as opposed to the Log 10 o….
I think 2.303 x Log 10 = Log e, but I could be wrong. Can’t remember what I used them for now…..Logs are easy to explain, by the way. They are just the power to which you raise 10 to get the number in question.

Oh, and I do enjoy maths. I’d rather solve quadratic equations than solve crosswords if I’m honest……

 

[Dave Ward]

the nmenonic for remembering them?

All Silly Tom Cats! - positive quadrants!
A planometer was a mechanical device for measuring the area under a curve - not unlike a precision pantograph. Indicator cards were the plot of pressure vs stroke in a 2-stroke engine - the planometer was used to give the power. You sometime see engine power des.cribed as ihp. or bhp. one being the theoretical power produced by the engine, the other being the useful power.. The indicator cards were taken by another fancy mechanical piece of kit - a Dobbie McInnes Indicator. Very tricky to use,- thankfully superseded by electric strain gauges - which would give continuous readings. The old machines only gave a power reading at one instant & it took about 20 minutes a cylinder to set up & record - not good, when you had 8 cylinders!
Dave

 

[Tim Marlow]

Nice one Dave. I was thinking of SOHCAHTOA, oops! Some Old Hairy Camels Are Hairier Than Others Are…….my maths teacher was a huge Southampton fan, so we had another that started Saints On High, but I cant remember the rest

 

[Jim R]

A friend of mine showed me the impressive model of Mount Everest that he had just built. I asked if it was to scale, he said, “No, it's just to look at”.

 

[boatman]

OH Well the brains have spoken (sigh)

 

[Guest]

Sine tables are very useful in trigonometry and I can’t really see how you can use a calculator to derive them if you don’t know how they work.

You type in the angle and press the SIN button, or work out the sine from the sides of the triangle and press INV followed by SIN. You still need to know how to do it, but you don’t need tables to tell you which angle goes with which sine value.

Go on then Dave…..what was the nmenonic for remembering them?

In Dutch: SOSCASTOA — Sinus is Overstaand gedeeld door Schuin, Cosinus is Aanliggend gedeeld door Schuin, Tangens is Overstaand gedeeld door Aanliggend. Which looks to be the equivalent to your SOHCAHTOA, which I had never heard of before just now

 

[Tim Marlow]

In Dutch: SOSCASTOA — Sinus is Overstaand gedeeld door Schuin, Cosinus is Aanliggend gedeeld door Schuin, Tangens is Overstaand gedeeld door Aanliggend. Which looks to be the equivalent to your SOHCAHTOA, which I had never heard of before just now :smiling3:

:thumb2:
Basically
Sine = Opposite over Hypotenuse,
Cosine = Adjacent over Hypotenuse,
and Tangent = Opposite over Adjacent.