# Trying out metric

Discussion in 'The Shop' started by potman, Dec 20, 2009.

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1. Dec 20, 2009

### potman

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So, if I'm going to make an engine I'm going to need a shop.
If I'm going to have a shop I'm going to need a workbench.

Went to the store today and got materials for a workbench.
Saw a tape measure with a metric scale.
Thought I might as well start getting used to metric measurements.

WOW, this is cool.

Instead of 27 5/8 + 3 1/2 - 3/16 = ???
Paper and pencil time.
But 70.2 + 8.9 - 0.5 = 78.6
I can do that in my head.

However,,,
Just how long is 61cm?
How high to my waist, in cm?
I dunno ???

Gotta measure everything now.
No intuition at all.
This must be what it's like to be a young child.

earl...

Henry likes this.
2. Dec 20, 2009

### chillybilly

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join the mixed up mayhem!!!!!!!!!!! " 8'x4' of 12mm plywood please " :big:

3. Dec 20, 2009

### websterz

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A couple of quick rules of thumb...

Roughly 2.5 centimeters to the inch (2.54 but 2 1/2's close enough for raw stock)
1 meter = 39 inches (again, a close enough)

And the golden number 0.03937 for converting millimeters to Imperial.

10mm x .03037 = .393

3/8 (or .375) / .03937 = 9.52mm

4. Dec 20, 2009

### bentprop

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And though the nominal size is 2400x1200,the actual size of the sheet is 2440x1220!
Luckily I was edumacated in Holland,which has always been metric
Think yourself lucky you don't live in the times of Ell,Bushel,or pigs bladder :big:

5. Dec 20, 2009

### zeeprogrammer

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earl!

Where are you located? Could help us help.

Pics! Love to see pics of a workshop coming together.

6. Dec 20, 2009

### mklotz

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10/16 + 8/16 - 3/16 = 15/16

Add 27+3 and you've got 30-15/16

7. Dec 20, 2009

### Artie

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Metric is a good thing IMO, I was in school when we changed so Ive a little grounding in both but predominately metric. Because Im so used to it, its definately my preference and having everything in tenths is much easier to head calculate, again, just my opinion.

However, when I was an apprentice mechanic, we still did the old buddy up with an experienced older guy and Vince was my man. Vince was a specialist at engine building so whenever our shop got such work it was Vince (and his '*****'... me..). Vince was 'old school' so I learnt engines in thou. And today everything in my world is metric, cept engine specs...

Works for me... 40 thou per mm... simple enough.....

Artie

8. Dec 20, 2009

### Tin Falcon

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I am with marv I used to work in a steel fab shop. The foreman was a very educated man, a dentist as a matter of fact ,but he used and needed a construction calculator to add fractions. I would do it in my head then check my numbers on paper well actually soap stone on steel. Doc just could not do it.
Tin

9. Dec 21, 2009

### GrahamC

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I guess I have just been lucky. I grew up with imperial measurements and in school it was imperial except for science which was Metric. So, when Canada went Metric it was an easy matter for me. Besides, I have always had a head for numbers, add, subtract, multiply, divide - decimals or fractions doesn't make a difference. I surprise my wife when she can get me out grocery shopping - in a basket with 50 or so items I will tell within a dollar what the total will be when she checks out.

I like to mix measurements just to throw someone off like I will ask the guy at the parts counter for a dozen M6 socket head screws 1-1/2" long.

And when asked how far it is to someplace (say it's 160km), I will tell them it's about 2 hours.

cheers, Graham

10. Dec 21, 2009

### ironman

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Is that magic number .03037 or .03937? I just ate dinner and my brain isn't on the ball for thinking right now?

11. Dec 21, 2009

### Deanofid

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Metric? Have fun with it, Potman.
It's just for folks who don't know their fractions, you know...
(nudge, nudge, wink, wink.)

Dean

12. Dec 21, 2009

### websterz

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.03937

13. Dec 21, 2009

### mklotz

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[pedant]

Actually, the magic number is 25.4, exactly. The inch is *defined* as 25.4 mm. Yes, that's right, the inch is defined in terms of the metric system. (As are many of the other basic units in the Imperial idiocy.)

1/25.4 = 0.039370078... is an irrational number. That means that the decimal representation goes on forever whereas the 25.4 representation is exact since that's how the inch is defined.

[/pedant]

Clearly, if one is simply estimating, none of this matters - calling a millimeter forty thousandths is good enough. However, if using a calculator, it's less keying to divide by 25.4 than to multiply by 0.03937. Further, most people seem to have less difficulty remembering 25.4.

14. Dec 21, 2009

### jimmyocharlie

#### Guest

i work in both metric and imperial!

i run CNC's, some are programed in metric and some imperial!

altering an offset to take thou off, is either 0.001 or 0.025! it can make it an interesting night when you are running one of each :big: :big: :big: :big:

wheights still catch me out though, in England its all metric, doing the shopping online i've bought a Kilo of mushrooms (thats a LOT!), pounds and ounces makes sense, but Kilos..............................

15. Dec 21, 2009

### mklotz

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Come again?

Pints of beer, stones on the bathroom scale, and, IIRC, miles on distance markers?

Do you still use that hundredweight (cwt) that weighs 112 pounds?

16. Dec 21, 2009

### dieselpilot

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CNC runs in both. Just set G20 or G21 Right? I like metric. Too bad it's hard to find good metric lathes in the US at a hobbyist price.

17. Dec 21, 2009

### potman

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What makes a lathe "metric" ???

Is it just the gearing for the screw thread, and
the calibration on the handwheels?

Or is there more to it ?

earl...

18. Dec 21, 2009

### Noitoen

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Isn't it enough? Working with fractions to me ......... :rant:

19. Dec 21, 2009

### dieselpilot

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Yes, metric leadscrews and dials on the ways and a metric threading lead screw. I work in inches while turning parts no problem, but threading is not so simple. I have to come up with some change gears. I do have a small CNC mill and just received a thread mill. I'm going to try thread milling in the mill.

20. Dec 22, 2009

### Deanofid

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Talk about getting your moneys' worth. 'Course, that would make me even fatter than I already am..

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