# Imperial vs. Metric

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#### jd2cylman

##### Still not Carl... ;-)
TRF Supporter
I'll start this since part of this discussion is clogging up the funny thread. As a mechanic for a company that's global (New Holland Construction), I have to deal with this all the time. Heck, some machines have metric and standard (our term for Imperial) on the same unit. NH engines are all made by a Fiat conglomerate, so they're all metric; mostly... I just had the exhaust manifold off an engine. The studs were definitely metric, but the external size was 7/16" or 11 mm. Both fit fine. In fact, I'm not sure, but I think the 7/16" fit better. Now we used to have 13mm and 19mm wrench sizes in a lot of the hardware. Now a lot of it is 15mm and 18mm wrench size. All the manuals give metric specs first and standard in ().
Torque is the biggest PITA. Mostly it's in newton meters which are .74 ft lbs. But I did have one that was kg force meter. Converting that was a REAL PITA...

#### dhbarr

##### Amateur Professional
That's ridiculous! How many ounces was that 29mm rocket last fortnight?

#### kuririn

##### BARGeezer
TRF Supporter
That's ridiculous! How many ounces was that 29mm rocket last fortnight?
Don't you mean how many grams was that 29 mm rocket?
Or how many ounces was that 1.15 in. rocket?
When I was in middle school the guvmint was preparing every citizen for the big metric conversion.
Gas stations pumps started showing liters instead of gallons.
The metric conversion never happened. Fine with me.

#### jd2cylman

##### Still not Carl... ;-)
TRF Supporter
That's ridiculous! How many ounces was that 29mm rocket last fortnight?
The rocket stuff actually is helping me think in both units nowadays...
The problem is having to own $50,000.00 in metric tools along side the$75,000.00 in standard tools I had already. If we were just one or the other it wouldn't be so bad.

#### mbeels

##### Yes balsa
TRF Supporter
And how about that story of the Mars Climate Oribiter, crashing because of a unit mismatch:

"The navigation team at the Jet Propulsion Laboratory (JPL) used the metric system of millimeters and meters in its calculations, while Lockheed Martin Astronautics in Denver, Colorado, which designed and built the spacecraft, provided crucial acceleration data in the English system of inches, feet, and pounds. JPL engineers did not take into consideration that the units had been converted, i.e., the acceleration readings measured in English units of pound-seconds^2 for a metric measure of force called newton-seconds^2."

#### jd2cylman

##### Still not Carl... ;-)
TRF Supporter
I can't tell you how many times I've found standard bolts jammed into metric threads on machines and equipment I'm repairing.
The other thing that's a whole lotta fun is hydraulic fittings...
There's American taper pipe, American flare, American inverted flare, American ORB, American port thread, American JIC, British straight, British tapered, German DIN, Japanese flare, Japanese British straight inverted flare, and a crapton more that I try to avoid... Like Japanese flange and Standard flange. Those are on the high pressure lines of excavators. And the o-rings don't like to be interchanged... Makes my job fun.

#### cherokeej

##### Well-Known Member
Decades ago, spent 6 months driving a mobile service truck for the employer, doing road calls. It's a big ol' mid-80's GMC, with a service bed, a liftgate, and a big compressor. Finish a road call, hop in the truck, and head down the road. I notice the voltage in the truck is down, must be a problem with the charging system. Pull over, pop the hood, and find the alternator belt flopping loose. No big deal, I'll just grab the pry bar, pull on the alternator, put a wrench on that 9/16" nut, and cinch that puppy.

Doesn't fit. Damn thing is a 14mm. Under the hood of a GMC pick-up truck. Mix-and-match! Too much fun. OK. Time to break out the Okie Speed Wrench.

More fun than that is the employer telling everyone in the shop "We're buying some metric coaches. Go buy metric tools."

And the tool-truck guys are drooling and wringing their hands outside the shop...

#### OverTheTop

##### Well-Known Member
TRF Supporter
The other thing that's a whole lotta fun is hydraulic fittings...
Have to agree there. Metric and all flavours of imperial. Ugly.

And the tool-truck guys are drooling and wringing their hands outside the shop...
Buy Metrinch spanners/sockets. You will wish you had done it sooner rather than left it to now. They suit both metric and imperial bolts/nuts. I have some of the combination spanners and they work a treat.
https://metrinch.com/metrinch_en/

I have been thinking of rationalising my spanners/sockets, and purchasing a full set of these. My workshop will be far more organised when I do it. There would be at least three toolboxes of spanners I can flog on eBay.

#### djs

##### Well-Known Member
Most of my work is with people in Europe, so I'm learning to convert measurements in my head (at least weight and distance). Fortunately it's mostly written stuff - I'm not fixing machines like jd2cylman.

Those metrinch tools are very cool.

#### Nytrunner

##### Pop lugs, not drugs
TRF Supporter
So instead of exactly fitting one or the other, it'll kinda fit both?

#### dr wogz

##### Fly caster
haha..

I'm Canadian, so I'm versed in metric. But pretty much everywhere I've worked has to deal with the American Supplier & Consumer, so we work in 'standard' / imperial. So, I'm pretty ambidextrous in regards to linear measurements.

Metric is easier, as it's all base 10. Imperial differs depending on the unit of measure.

if you look up "who uses imperial" you'll see that only the US, Burma & Liberia use the imperial system. The rest of the planet is SI or DIN standards.

But, while the US did try to change over to metric, there was much resistance and it was soon dropped for whatever reason..

The US also have a love of unique [archaic] 'systems': Sheet steel gauge, wrought iron gauge, pipe dia & sizing, AWG, etc.. While a 'number' is assigned, it has no relevance to its actual size. Look at a standard 1/4" pipe (not a tube). Neither the ID or the OD are 1/4"!

#### Crumb fire

##### Well-Known Member
Well, in my case, most of my work is in metric (in Canada we changed from imperial to metric in ~'78) and the material I build is for U.S companies. Kind of the opposite you are having. I have every tool sets in both metric and standart, except for torque. This one is a PITA.

Our measuring tape all have both system.

With time, I learned every conversion in my head, except for conversions I don't use (psi, volume, etc.)

Our houses are build in standart systems, since some materials are built for usa like lumbers and the like.

We get used to it, but one system would be better.

#### jjwb22101

##### Flying on a student budget
And how about that story of the Mars Climate Oribiter, crashing because of a unit mismatch:

"The navigation team at the Jet Propulsion Laboratory (JPL) used the metric system of millimeters and meters in its calculations, while Lockheed Martin Astronautics in Denver, Colorado, which designed and built the spacecraft, provided crucial acceleration data in the English system of inches, feet, and pounds. JPL engineers did not take into consideration that the units had been converted, i.e., the acceleration readings measured in English units of pound-seconds^2 for a metric measure of force called newton-seconds^2."
Saw a post on here about metric/imperial units, immediately looks for mention of MCO, am not disappointed. Whatever you choose, it doesn't matter, as long as you're clear and consistent.

#### Zeus-cat

##### Well-Known Member
The biggest problem with Imperial is the fractions. I hate 'em. I hate 'em. I hate 'em.

So my board is 5 and 13/32" wide and I need to cut it in half and the blade is 1/8" so that means... I need a calculator to figure out the proper dimension! Three college degrees (all in math and engineering) and I don't trust myself to do that calculation correctly!

#### jlabrasca

##### Well-Known Member
D
The metric conversion never happened. Fine with me.
Yes, imagine the confusion if we didn't have to understand that the price per ounce for butter is a based upon a different unit (a different dimension, even) from the price per ounce for ketchup (Or is it? And what about jelly? And do we price jars of whole pickles by the oz. or by the fl. oz? Is this different from pickled cucumber relish?)

The kilogram is dead: Long live the kilogram

#### Matt_The_RocketMan

##### Well-Known Member
Children, we all live in a imperial world stop the bickering and convert your children to the Jedi system now! Before its to late!

##### Well-Known Member
I grew up imperial, I know it and use it. All my co-workers are global and so I have to convert things in my head all the time. I wish the US was metric. Much easier to do math in my head on base 10.

#### kuririn

##### BARGeezer
TRF Supporter
Yes, imagine the confusion if we didn't have to understand that the price per ounce for butter is a based upon a different unit (a different dimension, even) from the price per ounce for ketchup (Or is it? And what about jelly? And do we price jars of whole pickles by the oz. or by the fl. oz? Is this different from pickled cucumber relish?)
Yeah, but you know how it is: people are more comfortable with what they are used to, not what is the most logical or efficient. How many times over the decades has someone come up with a better layout for keyboards?
And we are still using QWERTY.
Even on our cell phones and tablets.
Try convincing a geezer like me to do things "better".
Good luck.

#### jlabrasca

##### Well-Known Member
Yeah, but you know how it is: people are more comfortable with what they are used to, not what is the most logical or efficient. How many times over the decades has someone come up with a better layout for keyboards?
And we are still using QWERTY.
Even on our cell phones and tablets.
Try convincing a geezer like me to do things "better".
Good luck.
As discussed -- ad nauseam -- elsewhere on the forum, there is nothing particularly efficient or logical about SI (metric) units. The justification, definition, and realization of the units were all in response to the tangle of units (with very local realizations -- are barley grains the same length and weight from country to country, and do they change from year to year) used in different places.

We have to communicate quantities to one another all the time: how much should I buy? Am I a healthy weight? About how tall was he? About how far away, and about how much does it cost, etc. Even the least mathematically inclined will still talk about an inch, a mile, a ton, when comparing quantities.

I am just about finished with The Catalog of Shipwrecked Books. There is mention in there of a slim volume by Gulielmi Budae in which he worked out the value, in contemporary units, of Roman weights, measures, and currency. It was, in its day (the late 15th century), a best-seller -- because it allowed readers of classical works to make sense of these quantities.

Moving between just two systems is no trouble at all, compared to what folks up until the 18th century had to face; A world where the definition of a bushel varied from one American colony to another, and no two countries could agree on the length of a mile.

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#### Nytrunner

##### Pop lugs, not drugs
TRF Supporter
and no two countries could agree on the length of a mile.
Simple! The distance covered by a sprightly snail in two weeks time! (assuming it could maintain a pace of 8 furlongs per fortnight for the duration)

#### jlabrasca

##### Well-Known Member
Simple! The distance covered by a sprightly snail in two weeks time! (assuming it could maintain a pace of 8 furlongs per fortnight for the duration)
Funny. Also in The Catalog of Shipwrecked Books is a discussion of Hernando Columbus' role in a negotiation between Portugal and Spain on how the world was to be divided between the two countries. During this conference, he pointed out that Ptolemy's measurements of the circumference of the earth were figured in "stade" -- which was defined as the distance a man could run on one breath. The argument turned on whether or not the Portuguese were overstating the value of a stade, and Columbus did the math to show that a Portuguese estimate meant that people in Roman Alexandria could run for tens of miles at the equivalent of 17 miles per hour.

It struck me, when I read that passage, that the author was converting from whatever unit Columbus offered (leagues, or statute miles, or furlongs...) into modern miles.

Really, I plan to recommend this book to friends and colleagues.

#### jqavins

##### Gone beardless since then
TRF Supporter
Well, in my case, most of my work is in metric (in Canada we changed from imperial to metric in ~'78)
And yet, while visiting Ottawa from the US a few weeks ago and finding myself in urgent need of a new pair of pants, I learned that the pants in a Canadian store are sized by waist and inseem in inches, just like at home. As a visitor I find that lengths and masses are given in a freewheeling mix, sometimes English and sometimes metric. I wonder if sometimes the English units are considerately used for my benefit, but not even Canadians are so nice that they'd remark the sizes of all the pants in the store when they saw me coming.

As for the Mars probe, there will never be a shortage of stupid mistakes that can bring one down. Once upon a time in FORTRAN, all variables whose names started with the letters I, J, K, L, M, or N were integers and all others were real unless explicitly declared otherwise. And a different Mars probe was lost because someone didn't explicitly declare otherwise. Such stories will persist long after all countries and industries use the same units.

#### OverTheTop

##### Well-Known Member
TRF Supporter
So instead of exactly fitting one or the other, it'll kinda fit both?
They actually drive off the face, rather than on the corners like normal spanners/sockets. That makes them work over a range of sizes. They work very well on difficult nuts/bolts with corners rounded off.

#### Nytrunner

##### Pop lugs, not drugs
TRF Supporter
They actually drive off the face, rather than on the corners like normal spanners/sockets. That makes them work over a range of sizes. They work very well on difficult nuts/bolts with corners rounded off.
Fascinating, I'll have to look into them

#### cherokeej

##### Well-Known Member
Those Metrinch wrenches are cute, and might be something to check out. But right or wrong, they would need to be demonstrated over a period of time before a shop full of professionals will embrace them. Just one rounded off bolt or nut...
The guys in the shop where I worked were absolutely merciless. You round off the nut on that exhaust manifold with an "experimental" tool, you'll never hear the end of it. (Like Bob... Standing there one morning for four hours trying to drill a hole in a steel stanchion, with the drill motor running in reverse. For the next 12 years, until he retired, the only name that man ever heard was "Backwards Bob." You earn a tag in that shop, you keep it. Forever.)

#### HASTE

##### Well-Known Member
I've read through this topic and growing up in rural Australia through the 70's onwards have enjoyed many a discussion some rather heated ( both Celsius and Fahrenheit) on this same topic .
Both have their merits and their issues.
But as I sit here and nurse my 11 yo Dobermann of rapidly failing health I thought "she don't care if its a 9 liter bucket bucket or it contains 2 gallons of water or if her next meal is a 8 ounces of steamed chicken or 250 grams.
This will always be as similar as " Ford v Chevrolet v Dodge" .
Also a cross reference to the post in "Post a pic that makes you Laugh , the drug dealers cant work it out either herbaceous sellers use quarter, half and ounce and the powder monkeys use point, gram and kilo !
And at the end of the day its always going to be "damn hot ,to far away or too bloody heavy " no matter which system we use.

##### Well-Known Member
TRF Supporter
Metric is easier, as it's all base 10. Imperial differs depending on the unit of measure.
Metric is for people who can't do fractions.

The best, practical lesson I've ever seen in using fractions was from an American shop teacher, who did everything in standard units.

#### jqavins

##### Gone beardless since then
TRF Supporter
And at the end of the day its always going to be "damn hot ,to far away or too bloody heavy " no matter which system we use.
There are only seven temperatures as far as weather is concerned: effing cold, cold, chilly, nice, hot, damn hot, and damn effing hot.

#### KennB

##### I-95 Envoy
TRF Supporter
The company at which I work uses both systems. The company started in the US in the late 50's-early 60's using imperial units. After some cooperation and competition with a foreign company (and other sidetracks along the way) we are now majority owned by that foreign company whose designs are in metric. We issue our installation drawings to our customers in metric units but our shop works in imperial units. When we convert our metric numbers with tolerances to imperial, we make sure the tolerance band is tighter on the imperial so we stay within the metric requirements. BTW, for some dimensions (mostly shaft/hub fits), we have four-decimal place tolerances on our imperial measures, three-place on the metric.