Attila Kinali

What's with the obsession of USians to measure thicknesses in ounces?

I can kind of understand measuring copper thickness of a PCB in oz/ft^2, as that is easier to measure than actual thickness in the µm range. Especially if you don't care about the thickness being even.

But who the f*** came up with the idea of measuring leather thickness in oz? What thickness is an 5oz leather? And does that change with each leather type or do you just pretend it's some ideal animal hide of known density?

Jun 2, 2024 at 1:21pmWeb
Show threadAttila KinaliJun 2, 2024

The only measure more ridiculous than this, that I know of, is measuring nails in pence. Yes, the price that nails had somewhen in the 18th century is the way how nail thickness and length are measured. Today. In the 21th century.

🤦‍♂️

#SIunits

Show threadpenguin42Jun 2, 2024
@attilakinali The 'ton' of cooling is my favourite in the weird US units.
I guess well calibrated scales were about the only well calibrated thing they had.
Show threadAttila KinaliJun 2, 2024

@penguin42 Ton? Cooling?

*one wikipedia later*

What. The. Actual. F**k.

As for scales being calibrated: Getting calibration weights that give you better than 3 digits is a rather new thing. These weren't available to most people until after WW2. If you go for standard weights, these are only accurate to 2-3%. Some are as far as 5% off. That's still considered acceptable for day-to-day use. I don't dare to imagine what kind of weights people used in the US before industrialization.

Show threadpenguin42Jun 2, 2024
@attilakinali 'What the actual. F**k' - crazy isn't it 🙂 OK, but you say 5% - what accuracy do you reckon a farmer could measure the thickness of their leather to?
Show threadAttila KinaliJun 2, 2024
@penguin42 Vernier calipers give 100µm +/-10ppm. These were definitely available in the18th century. Though I'd expect anyone doing measurement of sub-10mm length/thickness to have something like a dial gauge giving 10µm +/- 10ppm. These were available in the 18th century, but probably not widespread until the late 19th century. So we are at better than 1% at 1mm thickness and getting better for thicker materials. Today these dial gauges are standard in leather working and cost nothing.
Show threadAttila KinaliJun 2, 2024
@penguin42 Compare this to the accuracy of a weight scale that is limited by the density of leather that can vary between 0.4 to 1.5 kg/m^3.. i.e. has a variability >300%
Show threadpenguin42Jun 2, 2024
@attilakinali I can see how a set of calipers (or even a simple slot gauge) would let you check the thickness at the edge of a piece of fabric/sheet/cow ; but how do you check someone hasn't cheated by making the edges thicker than the middle?
Show threadAttila KinaliJun 3, 2024
@penguin42 You never measure the edges of something, as there is always some fraying, burs or similar that makes them thicker. That's why calipers jaws are always shaped, so measure only in a small area and can exclude the edge.