Sort of true. There are a lot of cars that still have imperial which doesn't help, and there still seems to be a lot of other products that are non-metric. I guess it would be a little easier, maybe. It is a choice you make and then run with.
Are you using metric or SAE stuff to build rockets?
- Thread starter Kelly
- Start date
Help Support The Rocketry Forum:
I use metric when I don't want to worry about subtracting fractions and use imperial when i want to visualize size. My understanding from my relatives is that Canadians still use sq feet for real estate purposes. I guess it's easier to visualize a sq foot rather than a sq meter or sq centimeter.
Dipstick
Well-Known Member
- Joined
- Jan 20, 2009
- Messages
- 812
- Reaction score
- 362
Yup that makes sense...in my local (rural) area the directions to a location are always pretty funny. "Go 2 miles north, then turn right and in about 200 meters you'll get the driveway. Turn north an follow the driveway for about a quarter mile to the shed...and so on."
o1d_dude
'I battle gravity'
Whatever you do or say, never call an Australian a “pommie”.
Fighting words: ”Prisoner of Majesty”.
I thought it was prisoner of mother England, pome, originally, but yes you are absolutely correct!
Sabrina
The WildChild
- Joined
- Dec 19, 2015
- Messages
- 241
- Reaction score
- 171
JUST FOR FUN - Thoughts from a High School girl. 
I only have one set of tools.
It doesn’t matter what brand of watch you wear or what country you are in, an hour is an hour all over the world. - Common sense says this should apply to other types of measurement
It doesn’t matter what make or model of new car you just bought, or what country you are in. If you want to turn a wrench on that car you only need one set of tools. - This is already universally true - or mostly true.
Ask a friend or neighbor in the USA “ how many 1/16 of an inch are in ten miles?” and you will get a blank stare. Many won’t even know HOW to begin to calculate something like that. You won’t find anyone that can do the math in-their-head.
Find someone familiar with the metric system and ask – “How many millimeters in ten kilometers?” the answer is ten million, even I can do that one in my head.
I go about 110 to 115 on the freeway driving to work. You do too – Just look at your speedometer.
This one will really blow your mind. About 6 or 7 years ago in the USA a “standards” change was made. (happened in 2013 - but if you're not a scientist, you probably never heard about it) The USA no longer bases measurement like gallons or pounds or feet on some old dead British kings’ shoe size. Officially in the USA measurement is defined using the SI standard. What does this mean?
Example: Since 2013 a “yard” (yardstick) is officially and legally defined as 914.4 millimeters in the USA.
Don’t believe me – do some research. Not sure what “SI” is – research.
Don’t look now, the USA is already SI – extinction just takes a while. My prediction… by the time I get to retirement (I’m 17 now) I’ll go to the museum to see dinosaurs and 9/16 inch wrenches.
- yeah I know, haven't posted in a while - been busy with ONLINE school - been studying online since 2019 (BP) before pandemic -
I only have one set of tools.
It doesn’t matter what brand of watch you wear or what country you are in, an hour is an hour all over the world. - Common sense says this should apply to other types of measurement
It doesn’t matter what make or model of new car you just bought, or what country you are in. If you want to turn a wrench on that car you only need one set of tools. - This is already universally true - or mostly true.
Ask a friend or neighbor in the USA “ how many 1/16 of an inch are in ten miles?” and you will get a blank stare. Many won’t even know HOW to begin to calculate something like that. You won’t find anyone that can do the math in-their-head.
Find someone familiar with the metric system and ask – “How many millimeters in ten kilometers?” the answer is ten million, even I can do that one in my head.
I go about 110 to 115 on the freeway driving to work. You do too – Just look at your speedometer.
This one will really blow your mind. About 6 or 7 years ago in the USA a “standards” change was made. (happened in 2013 - but if you're not a scientist, you probably never heard about it) The USA no longer bases measurement like gallons or pounds or feet on some old dead British kings’ shoe size. Officially in the USA measurement is defined using the SI standard. What does this mean?
Example: Since 2013 a “yard” (yardstick) is officially and legally defined as 914.4 millimeters in the USA.
Don’t believe me – do some research. Not sure what “SI” is – research.
Don’t look now, the USA is already SI – extinction just takes a while. My prediction… by the time I get to retirement (I’m 17 now) I’ll go to the museum to see dinosaurs and 9/16 inch wrenches.
- yeah I know, haven't posted in a while - been busy with ONLINE school - been studying online since 2019 (BP) before pandemic -
Keenan Cox
Active Member
- Joined
- Oct 11, 2018
- Messages
- 27
- Reaction score
- 10
It's a mix for me. I used SAE for most everything for many years, but my job is almost entirely metric, and has pushed me that way for anything smaller scale. When I want exact measurements, or where it's more important, I'll stick with metric, and when it's a rough measurement, SAE does the trick. Job-dependent, I'd say.
I'm so old I have two sets of tools: Metric and Imperial. I still look at a 14mm bolt and go, 'Well, that's about 9/16ths.'
Working with both systems is easier than a lot of people think, and if I win the Lottery I'll be buying a Triumph X-75 Hurricane and then I'll need those Imperial tools!
I have my dad's tools too, so I have metric, and imperial (SAE and Whitworth).
Maybe, but we can all hope.
Not many people realise that the SI system crept in like that.
Both. I prefer metric but flex to the design.
user 30299
L2 - NAR & TRA
- Joined
- Nov 6, 2019
- Messages
- 963
- Reaction score
- 903
Nothing like an old Hoover vacuum cleaner for restocking my nuts, bolts and screws supply. Nothing goes to waste . . .
- Joined
- Mar 27, 2013
- Messages
- 22,535
- Reaction score
- 14,942
Mostly SAE, but metric for my bicycle.
Nice writeup! The US definition of the inch is now exactly 25.4 mm, and (I think but may be wrong) other imperial length units are defined according to that. That is, the yard is still defined as 36 inches. (At least that's how I and coauthors describe it in Chemistry for Changing Times 15th ed
).FWIW technically, SI (French, Systeme International) bases all measurements (and other derived units) solely on the seven base units. A diameter, whether atom or Sun, is expressed in meters. Mass of a flea or a mountain in kilograms. Time is in seconds, etc. A joule is one (kg m^2)/s^2 and is the only energy unit used in SI. SI makes unit issues per se almost impossible. Of course it's only used in the sciences, and even then not by every scientist. Prefixes (i.e., metric system) size the unit down or up and are far more convenient for most measurements.
1 kilosmile = 1000 smiles
Terry
- Joined
- Jan 7, 2019
- Messages
- 1,353
- Reaction score
- 1,019
Both, either. Sometimes you buy one part and it's metric, so you have to use metric. Same with imperial. I bit the bullet and bought an inexpensive (aka, plastic) screw gauge that has both imperial and metric sizes. Now all I need to do is buy a metric drill/tap set and my toolkit is complete.
Just like screws should be listed with their thread major and minor diameters, and we should all move on from this pointless "number whatever" relic.
I don't know the diameter(s) of a BT-70 (in milimeters or inches) but I do know what one looks like. It's a handy verbal shorthand.
No, I don't believe you. I don't know what change was made in 2013, but the inch has been defined as 25.4 mm for a lot longer than that. (Or maybe it's the yard that's defined, and the inch is 1/36th of it.)
dr wogz
Fly caster
That 69oz bottle of coke?! yup, 2 liters!
Beer up here is still in pints though.. 473ml (16oz) for tall cans or 341ml (12oz) for bottles..
When Canada went metric back in the 70's, a lot of the music lovers cried. Milk crates, popular with vinyl-heads, fit standard (12") records of the time. The crates were designed to hold quarts & pints for milk. With the introduction of Liters (which are slightly smaller), the industry changed the size of their milk crates to suit. So, record no longer neatly fit in 'Canadian' milk crates..
as for other "silly" designations:
American Pipe sizing: a 1/2" pipe (not tube) is actually .84" in OD. and only when you get to 14" does it equal 14" OD!
Sheet metal gauges: which is thicker? 14GA or 22GA? (and what are they? does the material matter?)
Wire gauges as well.. what carries more current? 10AWG or 32AWG? (but the same can be said for the other "standard" wire gauges..)
One cool thing about SAE hardware: you know what wrench you need just by knowing the stud diameter:
wrench sizing = (2 * stud) - 1/16"
So, a 5/16" bolt requires a ( 2 * 5/16" ) - 1/16" = 10/16" - 1/16 = 9/16" wrench..
As for numbered machine hardware (#4, #6, #8, etc..) there is a relation, but I can't find it. I remember being told it many many years ago..
Socket head cap screws (bolts) also have a similar relation to the stud size & head diameter (and head height) so you knew if you had a 11/16" socket head cap screw, that your head would be X, and the height would be Y, and you could then work out the counter-bore hole you'd need to seat it..
Beer up here is still in pints though.. 473ml (16oz) for tall cans or 341ml (12oz) for bottles..
When Canada went metric back in the 70's, a lot of the music lovers cried. Milk crates, popular with vinyl-heads, fit standard (12") records of the time. The crates were designed to hold quarts & pints for milk. With the introduction of Liters (which are slightly smaller), the industry changed the size of their milk crates to suit. So, record no longer neatly fit in 'Canadian' milk crates..
as for other "silly" designations:
American Pipe sizing: a 1/2" pipe (not tube) is actually .84" in OD. and only when you get to 14" does it equal 14" OD!
Sheet metal gauges: which is thicker? 14GA or 22GA? (and what are they? does the material matter?)
Wire gauges as well.. what carries more current? 10AWG or 32AWG? (but the same can be said for the other "standard" wire gauges..)
One cool thing about SAE hardware: you know what wrench you need just by knowing the stud diameter:
wrench sizing = (2 * stud) - 1/16"
So, a 5/16" bolt requires a ( 2 * 5/16" ) - 1/16" = 10/16" - 1/16 = 9/16" wrench..
As for numbered machine hardware (#4, #6, #8, etc..) there is a relation, but I can't find it. I remember being told it many many years ago..
Socket head cap screws (bolts) also have a similar relation to the stud size & head diameter (and head height) so you knew if you had a 11/16" socket head cap screw, that your head would be X, and the height would be Y, and you could then work out the counter-bore hole you'd need to seat it..
- Joined
- Jun 8, 2017
- Messages
- 153
- Reaction score
- 148
Some other random things to consider: my slide calipers are in fractional inch and metric so I often end up using whichever system is closest to what i measured. Sometimes i can’t get the exact hole size i want with either Imperial or metric and so rely on letter/number drills (talk about archaic!). The phillips slots in most metric screws are actually JIS (Japanese Industrial Standard) so if you want a great, tight fit on those Asian screws buy a set of JIS screwdrivers. I bought nylon screws to use for shear pins. The x slots of the Imperial #2 screws were slightly deeper, crisper, and much better formed than the x slots of the M2 screws, even with the correct driver. I hate it when the T-nuts with imperial threads are otherwise exactly metric in the thickness and other material dimensions. The blind nuts in my friend’s Ford Transit van were all M6, not 1/4-20.
the world is a complicated mix of engineering babel. Use what works and forget this “freedom” baloney. Praise the gods that we didnt also end up with having to use an additional system like British Standard Whitworth. And dont even think about discussing wire and sheet metal gauges.
the world is a complicated mix of engineering babel. Use what works and forget this “freedom” baloney. Praise the gods that we didnt also end up with having to use an additional system like British Standard Whitworth. And dont even think about discussing wire and sheet metal gauges.
Pipe sizes are based on the ID, not the OD. Sort of. The size is supposed to be the diameter available for fluid, after allowance for corrosion. So the ID is slightly bigger than the nominal size. But that's for one particular wall thickness, I assume Schedule 40. The other wall thickness pipes have the same OD so that fittings are interchangeable, so the nominal to ID relationship is wrecked anyway.
A given sheet metal gauge means different thicknesses for carbon steel, carbon steel galvanized, stainless steel, aluminum, and copper/brass/silver. Wire gauge is different for copper, steel, and piano wire (a.k.a. music wire) even though that last is also steel. The wire gauge diameters are kinda sorta close to the sheet metal thicknesses.
And then there's shotgun bore diameter, also gauge, but totally different. It's the number of lead spheres with diameter matching the bore that it takes to make up a pound. And old cannon designations of 6 pounder, 20 pounder, etc. is the weight of a ball that fits the barrel. But wait, that's iron balls where the shotgun gauge thing is with lead balls. (I have to admit that the last point makes sense, since those are the ball materials used for the respective guns.)
For fasteners, almost always SAE. I made the decision a little while ago to use metric on a build because I could find smaller welded eye bolts and more variety in heat set threaded inserts at Amazon, but then couldn't find screws to match the inserts without a captive washer and had to go to McMaster anyway. I've also got much better odds of finding hardware locally if I want SAE. So I'm back to the dark ages.
For 3D printed stuff, I've got functions mm() and mil(), and every measurement is passed through one or the other of them. So those projects are a complete mish mash in terms of the programming even though the slicer and printer are metric.
For 3D printed stuff, I've got functions mm() and mil(), and every measurement is passed through one or the other of them. So those projects are a complete mish mash in terms of the programming even though the slicer and printer are metric.
user 30299
L2 - NAR & TRA
- Joined
- Nov 6, 2019
- Messages
- 963
- Reaction score
- 903
You forgot to add "Tubing" for hydraulic lines . . .
DAllen
Well-Known Member
Off topic time...
I work in road construction and recently discovered a rather significant boo-boo a surveyor made. There are 2 types of feet: US Survey Feet and International Feet. Plan coordinates were based on International Feet and the surveyor was using US Survey feet which resulted in a 25' migration of all the survey stakes to the east. Ooops. Fortunately this was very early in the project so nothing had been built off of this error.
I work in road construction and recently discovered a rather significant boo-boo a surveyor made. There are 2 types of feet: US Survey Feet and International Feet. Plan coordinates were based on International Feet and the surveyor was using US Survey feet which resulted in a 25' migration of all the survey stakes to the east. Ooops. Fortunately this was very early in the project so nothing had been built off of this error.
dr wogz
Fly caster
Yes, Joe, very true on all counts.
I was bringing them up as examples of how "silly" some of these things seem to be, unless you know the history behind them. Not many would realize that there is a difference between a "pipe" and a "tube"..
But for arguments sake, (and that I have the 26th edition of the Machinery's handbook at my fingertips): .. size is based on a standardized OD. .. so that the ID is nominal with the materials of the time .. Although there is now no such relation .. these nominal sizes continue as "standard" ..
So, you do need to know a bit to make an informed choice. (How many home plumbers have gone to the store to get a new toilet supply line, and look at the ends and thought: "that's a 1/4"?!?!!" ) Machinists & designers know to look for it, and do the math, knowing that a 1/2" pipe will be used for their machined part of 3/4" OD.. But we need to look up what a 1/2" sch 80 pipe is!
The sheet metal gauges, when compared to ISO (or DIN) standards, are just that: the material thickness. I know a 16GA sheet is .060" (0.0595" actually, for stainless steel) but that's because i use it every day. Any 'lay person' doesn't know that, and would assume it's close enough to 1/16" (or that the "16" is just that: 1/16"). But a metric sheet is 2mm or 1.5mm, and that's how it's referred to.... Again, no need to look up tables & such.
standard 1/4" glass, window glass: yup, 6mm (.234")
Just making an example of some things that should be updated to reflect "today".. To get away from standardized things from long ago (and outdated), and to make it so you don't need to be 'in the industry' to know.. There are many many more out there! And maybe it's time we start cleaning a lot of this up, and to try & standardize on what everyone else is producing.
Or at least communicate. The famous snafu on the NASA Mars Climate Orbiter was the perfect example of that.
And when you do teach physics, please be sure to teach dimensional analysis. I used it extensively and it’s a great tool to detect common mistakes.
Last edited:
Glad to see you back!JUST FOR FUN - Thoughts from a High School girl.
I only have one set of tools.
It doesn’t matter what brand of watch you wear or what country you are in, an hour is an hour all over the world. - Common sense says this should apply to other types of measurement
It doesn’t matter what make or model of new car you just bought, or what country you are in. If you want to turn a wrench on that car you only need one set of tools. - This is already universally true - or mostly true.
Ask a friend or neighbor in the USA “ how many 1/16 of an inch are in ten miles?” and you will get a blank stare. Many won’t even know HOW to begin to calculate something like that. You won’t find anyone that can do the math in-their-head.
Find someone familiar with the metric system and ask – “How many millimeters in ten kilometers?” the answer is ten million, even I can do that one in my head.
I go about 110 to 115 on the freeway driving to work. You do too – Just look at your speedometer.
This one will really blow your mind. About 6 or 7 years ago in the USA a “standards” change was made. (happened in 2013 - but if you're not a scientist, you probably never heard about it) The USA no longer bases measurement like gallons or pounds or feet on some old dead British kings’ shoe size. Officially in the USA measurement is defined using the SI standard. What does this mean?
Example: Since 2013 a “yard” (yardstick) is officially and legally defined as 914.4 millimeters in the USA.
Don’t believe me – do some research. Not sure what “SI” is – research.
Don’t look now, the USA is already SI – extinction just takes a while. My prediction… by the time I get to retirement (I’m 17 now) I’ll go to the museum to see dinosaurs and 9/16 inch wrenches.
- yeah I know, haven't posted in a while - been busy with ONLINE school - been studying online since 2019 (BP) before pandemic -
I forgot nothing, but I figured enough was enough. I stopped before going into copper water pipe - er, tube - and if hydraulic line tubing is different yet I 1) didn't know that, and B) wouldn't be a bit surprised. (Didn't know is a different thing from forgot.)
And Paul, yes my point also was to point out how silly some of these are and have a laugh. For the home owner looking at a toilet line and saying "That's 1/4"?", I had the opposite problem. I got used to pipe sizes and routinely understated the size of other things. "Looks about like 3/4" pipe, so I guess it's 3/4 of an inch." Now that I've learned better, my mental reference for 3/4" is the thickness of a 1× board.
And why is a long cylinder used to carry water called a pipe if it's iron and a tube if it's copper? And the same (well, nearly the same) piece of iron is called conduit if it's got wires inside.
It's a mad house! A mad house!
Doug Holverson
Well-Known Member
- Joined
- Jul 4, 2012
- Messages
- 655
- Reaction score
- 595
Hodge-podge of both. Metric is easier to calculate and CAD. SAE is what's available at the hardware store. Many of my little pieces are schizophrenic both. Like the indexed Omni-Pad head that I'm attempting to 3D print.
Thinking about schizophrenic, how about the old MPC and AVI come Quest body-tubes with the metric diameters and SAE lengths.
Then I've owned a few Pintos in my life. SAE body and rear axles with the rest of the drive train being mostly metric.
Thinking about schizophrenic, how about the old MPC and AVI come Quest body-tubes with the metric diameters and SAE lengths.
Then I've owned a few Pintos in my life. SAE body and rear axles with the rest of the drive train being mostly metric.
rharshberger
Well-Known Member
Actually tubing vs pipe is more a diameter thing not a material based. Smaller diameters of pipe are commonly called tubing and larger diameter are pipe. However that changes when the purpose changes from being a vessel being structural, now tubing is more like a round structural member.I forgot nothing, but I figured enough was enough. I stopped before going into copper water pipe - er, tube - and if hydraulic line tubing is different yet I 1) didn't know that, and B) wouldn't be a bit surprised. (Didn't know is a different thing from forgot.)
And Paul, yes my point also was to point out how silly some of these are and have a laugh. For the home owner looking at a toilet line and saying "That's 1/4"?", I had the opposite problem. I got used to pipe sizes and routinely understated the size of other things. "Looks about like 3/4" pipe, so I guess it's 3/4 of an inch." Now that I've learned better, my mental reference for 3/4" is the thickness of a 1× board.
And why is a long cylinder used to carry water called a pipe if it's iron and a tube if it's copper? And the same (well, nearly the same) piece of iron is called conduit if it's got wires inside.
It's a mad house! A mad house!
milehigh
Well-Known Member
- Joined
- Apr 26, 2016
- Messages
- 444
- Reaction score
- 301
I only build LPR where the SAE/metric hardware issue doesn't really come into play all that much.
However, I use Imperial measurements if I'm building a clone of a vintage Estes or Centuri design, mainly because the original plans/instructions were written thusly.
When designing my own birds, I tend to gravitate to metric. I will use imperial sometimes, but only in decimal divisions. This is particularly useful for scale models in which prototype drawings are dimensioned in inches.
I agree with many others on this thread that it is highly beneficial to be familiar with both measurement standards and utilize the one best suited to the current project.
However, I use Imperial measurements if I'm building a clone of a vintage Estes or Centuri design, mainly because the original plans/instructions were written thusly.
When designing my own birds, I tend to gravitate to metric. I will use imperial sometimes, but only in decimal divisions. This is particularly useful for scale models in which prototype drawings are dimensioned in inches.
I agree with many others on this thread that it is highly beneficial to be familiar with both measurement standards and utilize the one best suited to the current project.
Calling it pipe is something I've been called out on quite a few times, by different people in different places. Perhaps they were wrong? I know they're wrong in my heart, because that's a pipe, damnit.
Similar threads
