Britain said it was taking steps to return to the traditional system of imperial weights and measures

[Aaron_W]

I have a set of lenses for a view camera ,
one 90mm
one 203mm
one 5 1/4 inch

not confusing at all

Don't forget that standard 1/4"-20 screw for tripod mounting your "35mm" camera (film what's that? ) .

 

[B2]

Five snorts is a quirt. Seven quirts is a fritz. And on and on. Any measure is relative to what is being done. I was reading a book on Railway Locomotives published 1911. Which indicates the information is from 1910 or earlier. In a section about machining replacement parts, a unit of measure of 1/64th was common. That the 1/64 was "scant" or "full" implies 1/128. That's actually pretty close to 2 tenths of a millimeter.

Today we think in thousandths, why not in tenths of a millimeter. Or we think in tenths of a millimeter. . . The question goes on and probably will for generations into the future. A grain of sand from Florida is considerably different than one from Tahiti, which is different than. . .

Precision math (actually arithmetic) has its' place. If I were building a rocket ship to go to the moon, I might want calculations to five decimal places. But for my home tinkering, two places full or scant is close enough.

Mathematics comes into play when one studies algebra (and trig, on my own) and better. Addition, subtraction, multiplication, and division don't reach that high. And "long division" is something we all do on a regular basis. In the time it takes to reach for a calculator, we have already determined that 1/16 inch equals 0.0625 inch. 1/256 takes a little longer, but why bother with a calculator. A pencil and paper is already handy if needed. And in reality, making a bolt from hex stock deserves a sketch anyway.

I didn't go to high school, barely finished grammar school. But I much prefer long hand pencil and paper for no other reason than batteries don't last forever. And usually die when most needed. I do have a (several) calculaters. To figure the secant of 24.5 degrees does take a bit of calculation. But to bisect that angle, the result is 12.25 degrees. That is basic arithmetic.

End of rant

.

Google says the distance to the moon is: 238,900 mi, or 391,388 kilometers at the moment. 6 digits.... Lets see, if I understand 5 decimal places will get me to within ~10 miles of where I may need to be or is it even farther off. .... so get out the moon buggy. However, where in this conversation are the error bars? In this case 10 miles or so is good enough!? Yes, the proper way to do the conversion is to keep only as many decimal places as the original number.... 1.0 inches = 2.5cm, 1.00 inches is 2.54cm etc. Error bars are needed to know exactly what is meant. On the other hand if my mill has 0.007" of backlash why do I need to spec. a circular part to better than 0.001" . Certainly do not need to spec it at 0.0010. On the other hand, if I get a better mill..... some day....

Grain of sand. To day I finally figured out what sand was used in the mortar of my 90 year old house. I have been trying to match the color for years..... Having a hell of a time trying to match it without the original sand..... Monterey Beach Sand. It has a nice mixture of brown, clear ,, etc. grains. It is not white or grey or black like some others. The Monterey Bay Sand Company that may have mined it had to recently quit due to some complaints about erosion etc. So yes, sands are different.

 

[savarin]

When grinding my mirrors I work in fractions of a wavelength of light.

 

[higgite]

Speaking of useless metrics to the average hobby machinist.... millibars. I fail to see the purpose of the local TV weatherman informing me of the millibars of pressure in the eye of an incoming Cat 4 hurricane. I have been blown around by strong winds before, but I’ve never been hit by a millibar. I did hit a few minibars back in my travellling days, but that's a whole nuther system of measurement.

Tom

 

[skyline1]

This is just another bit of the typically British political rubbish we are famous for, mainly designed to frustrate and confuse the EU. (like they are not confused enough already)

In reality we have been using both systems in parallel since metrication first happened. even though it was technically illegal.

The only difference this will make is is that supermarkets will now be able to sell packets marked " contents 1LB (454 Grams)" instead of "contents 454 Grams (1LB)".

In engineering terms it will make little difference as we are doing these conversions already and and have been for decades either explicitly or mentally.

For example if my metric micrometer says my part is 0.1mm oversize then I know how much too big it is even if in my head I'm thinking about 4 'thou. as that is something I can visualize. In my case it's also about 2 hairs or 1/5 of a thumbnail. The actual units don't matter as much as the relative size

We tend to mentally convert to our preferred system of units instinctively often without knowing it.

Best Regards Mark

 

[rwm]

Tell that to the Mars Climate Orbiter team!

Mars Probe Lost Due to Simple Math Error

NASA lost its $125-million Mars Climate Orbiter because spacecraft engineers failed to convert from English to metric measurements when exchanging vital data before the craft was launched, space agency officials said Thursday.

www.latimes.com

Robert

 

[Larry$]

Metric fasteners come in those little bins, wrapped in plastic, and usually at about four times the price.

I do mostly repair work and got tired of needing to get expensive metric fasteners. I now have sets from McMaster-Carr. If I only use 1/10th of them it is cheaper than the local outlets and saves me trips. It also allows me to design & work in metric for my own projects. Over time I've torn apart metric stuff and always saved the fasteners, now stored in plastic, labeled jars.

 

[higgite]

Tell that to the Mars Climate Orbiter team!

Mars Probe Lost Due to Simple Math Error

NASA lost its $125-million Mars Climate Orbiter because spacecraft engineers failed to convert from English to metric measurements when exchanging vital data before the craft was launched, space agency officials said Thursday.

www.latimes.com

Robert

That’s not a problem with the system of measurement. That’s a problem with incompetent/careless engineers at JPL.

Tom

 

[RJSakowski]

I do mostly repair work and got tired of needing to get expensive metric fasteners. I now have sets from McMaster-Carr. If I only use 1/10th of them it is cheaper than the local outlets and saves me trips. It also allows me to design & work in metric for my own projects. Over time I've torn apart metric stuff and always saved the fasteners, now stored in plastic, labeled jars.

Unfortunately, I don't have enough call for metric fasteners to justify purchasing in bulk. I also save all fasteners, both metric and SAE from old machinery and equipment and I have a small stash. Most recently, I scrapped out about 6 tons of iron and pulled all the fasteners out. The cost of each fastener doesn't justify the effort by itself but when you factor in the 50 mile round trip and the 2 hours spent to get the fastener you need to finish a project, it makes sense.