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Re: metric drill set explained?

Posted: Tue Oct 02, 2018 7:35 am
by John Hasler
Harold writes:
My world, aside from the refining of precious metals, has always been Imperial.

Customary, actually. The US has never used the British Imperial system.

Re: metric drill set explained?

Posted: Tue Oct 02, 2018 9:56 am
by NP317
I've got ten fingers, and ten toes.
So goes measurement systems.

And to think that I used to be pretty good with the early computer hexadecimal system...
~RN

Re: metric drill set explained?

Posted: Tue Oct 02, 2018 11:58 am
by mklotz
Harold_V wrote:
Tue Oct 02, 2018 1:44 am

Lets here it for the Imperial system, metrics be damned! :P
Bite your tongue, Harold. Do you really want to use a system where...

A hundredweight weighs 112 lb.
There are seven definitions of a "barrel".
Foot-pounds and pound-feet measure different things.
Fluid ounce is a measure of volume, not weight.

And, yes, in the USA we use American Customary Units, not Imperial. I prefer to call them Inferial units, a portmanteau of Inferior/Infernal/Infuriating and Imperial.

To demonstrate to yourself how awkward Inferial units are, here are a couple of test problems to try...

Calculate (not look up) the number of gallons in an acre-foot of water.

The muzzle energy of a firearm is calculated from the following equation...

Energy (ft-lb) = (muzzle velocity (ft/sec))^2 * bullet weight (grains) / K

where 'K' is a constant. Calculate the correct value of 'K' to be used with the units shown.

Calculate the number of acres in a square mile working from the definition of an acre (the area of land a man can plow in a day - a furlong long and a chain wide).


Oh, and it's spelled "hear" :-)

Re: metric drill set explained?

Posted: Tue Oct 02, 2018 12:10 pm
by John Hasler
Marv writes:
And, yes, in the USA we use American Customary Units...

And SI. Every product container I can find in the house is labeled with both SI and customary units. People who say "The US should switch to the metric system" really mean "The US should outlaw the Customary system".

Re: metric drill set explained?

Posted: Tue Oct 02, 2018 12:25 pm
by WesHowe
John Hasler wrote:
Tue Oct 02, 2018 12:10 pm
People who say "The US should switch to the metric system" really mean "The US should outlaw the Customary system".
To quote John Lennon in response: "You say you want a revolution"?

Re: metric drill set explained?

Posted: Tue Oct 02, 2018 12:50 pm
by GlennW
I haven't discovered the flaw in the Imperial system yet!

I had a guy ask if I could make some parts for him to replace some broke parts. They were either hydraulic or pneumatic piston/shafts that were threaded externally on one end, so I said sure, no problem. When I got them apart and measured them they were all metric...

I gave them back and told him I don't dork around with metric threading since my lathe is imperial and I use it daily, and don't want to take the time to switch it over for metric threading and then back again.

Three weeks later he came back with the parts again and said he had been to every machine shop he could find in two Counties and nobody would touch them because they were metric. I was surprised, as I thought I was the only one that hard headed.

I agreed to make the parts, and being the first time I did any metric threading, it wasn't bad, just a bit more time consuming compared the Imperial threading. Having to noodle with change gears and pressing bushings and spacers in and out was a pita though, as well as using Imperial thread wires for metric threads...

I was surprises at the difficulty in finding someone that would do metric threading.

Re: metric drill set explained?

Posted: Tue Oct 02, 2018 1:55 pm
by whateg0
GlennW wrote:
Tue Oct 02, 2018 12:50 pm
...I was surprises at the difficulty in finding someone that would do metric threading.
I suspect that the reason for others, like you, was that they have machines setup for inches and not mm. That's the only real downside to threading in metric for many of us - we have a qc gearbox for switching between all the various tpi, but have to resort to change gears for mm/thread.

Dave

Re: metric drill set explained?

Posted: Tue Oct 02, 2018 4:02 pm
by Harold_V
tornitore45 wrote:
Tue Oct 02, 2018 6:49 am
They built the pyramids measuring cubits, just to say that is not a matter of accuracy or capability is simply a matter of practicality.
You can divide the cubit by 360 for a smaller unit and have a longer unit of 3631 cubits and still send man to the moon with such a system.
That, more or less, is what I've tried to say. Regardless of how clumsy a system may be, if you're familiar with it, and are not familiar with any other, it serves the purpose perfectly well.

Would like to thank those who pointed out that we do not use the Imperial system (in the US). For what ever reason, I assumed that's what it was called.

That said, for me, it borders on the impossible for me to use metrics, as I am not very familiar with them. I'll leave that for the younger generations, who may be raised with the system, just as I was raised with what ever the hell our system (in the US) is called. That's the devil I know, and it has served me perfectly well. :twisted:

H

Re: metric drill set explained?

Posted: Tue Oct 02, 2018 4:22 pm
by tornitore45
My father in law, an old dairy farmer, had a fit when he realized the "yard" stick he got as an advertisement for some feed product ended at 39 inches an a few lines close to 3/8. I was funny.

Re: metric drill set explained?

Posted: Tue Oct 02, 2018 4:35 pm
by John Hasler
I'm comfortable with both the metric and US customary systems but I use mostly customary in the shop because that's the kind of (old) tools and machines I have. Because I use it a lot I have a better intuitive feel for customary than metric, but I'm sure that would change quickly were I to start using mostly metric. This makes me a bit impatient with the more enthusiastic advocates of both.

The erroneous assertion that the USA uses the Imperial system is, unfortunately, very common. The inch, foot, and yard are identical in the two systems but other units differ.

Re: metric drill set explained?

Posted: Tue Oct 02, 2018 5:03 pm
by BadDog
whateg0 wrote:
Tue Oct 02, 2018 1:55 pm
I suspect that the reason for others, like you, was that they have machines setup for inches and not mm. That's the only real downside to threading in metric for many of us - we have a qc gearbox for switching between all the various tpi, but have to resort to change gears for mm/thread.
It's a bit more than just change gears. Even if you have a lathe like mine where you just throw a lever, there is the problem with the half-nuts needing to remain engaged. Even on a "metric" lathe, you can only open the half-nuts on a subset of in-use threads (at least 2 chaser gears required, maybe 3?). And I'm not sure that there aren't metric pitches that aren't possible (within a given tolerance) even with a transposing gear set. Also, beyond single point issues, for a given fastener size, there are very often more metric pitches in common use than with "standard" hardware. Some time back I was working on my Kubota where the PO had let quite a few fasteners vibrate out, and still more get sheared by resulting loose brackets, or twisted off (perhaps trying to "tighten enough" to stop loosening?). Anyway, the local dedicated fastener store ("Copper State, that's their core business) didn't have half of the hardware I needed. For example (going from memory, so YMMV) on a given bolt where it needed a 1mm pitch, the "standard" according to Copper State was 1.25mm, which is all they carried, so tough luck. I wound up buying a small bag of bolts from Kubota for something like $20, and that was after their shop guy who happened to be working the counter took pity and gave me some loose bolts from the back for the ones that were the most stupid priced (and required an order to be in some week or so later!). Given a choice, I'll take "standard" fastener hardware EVERY time. At least there you can get whatever grade you want, coarse or fine thread, and the worst problem I'm likely to have is that I might need to cut one down to get the prefect length. In my experience, not so with metric fasteners...

Re: metric drill set explained?

Posted: Tue Oct 02, 2018 8:59 pm
by WesHowe
Threading issues aside, metric is not bad, not good, just different. When I am working on a metric based machine tools (usually pronounced "chi-neez") I flip my micrometer and DRO to metric and machine in metric. Otherwise I work in "customary"" units, since that is what I grew up using. The arguments about the math being easier for metric are misleading applied to machining, because working in inches and thousandths is simple base-10 math, exactly like metric work.