Pocket tools

[mklotz]

If you encounter an unplanned-for shopping situation and don't have even your pocket gages with you, it's handy to memorize some measurements associated with material you may always have in your pockets.

A US penny is exactly 0.75" in diameter.

The US dollar bill is nominally 2.5 x 6". These dimensions are not held rigidly as is the case with the penny but are close enough for most purposes. With judicious folding one can construct impromptu "gages" of a number of different sizes. The diagonal of the bill is 6.5".

The typical business card is 2 x 3.5". Of course, there are bigger cards but most of us will have, due to years of exposure, a good "feel" for the typical size. Again, folding will produce other useful sizes.

Memorizing sizes of things you always have on your person is a good idea. The diameter of a wedding ring or the length of a pocket knife blade are typical examples.

While shopping, you may encounter metric sizes and, lacking a calculator, need to determine their inferial size mentally. I keep in mind that a millimeter is about 40 thousandths. Thus,

10 mm (1 cm) = 0.4"
30 mm = 1.2"
300 mm = 12" = 1 ft
etc.

Going the other way (metric to inferial) is as easy as dividing by 4 and multiplying by 100, which is, of course, the same as dividing by 0.040.

12"/4 = 3
3*100 = 300 mm

Finally, not nearly as useful for shopping, but possibly useful in the shop, is the fact that a US nickle weighs five grams. Easy to remember - five cents and five grams. An ounce (avdp) is 28.3 grams so six nickels is fairly close.