31–40 of 69 posts
Luckily we don’t really do PCB design in imperial anymore at any of the companies I’ve worked with (I hear even US companies are moving away from it since so much of the manufacturing is offshore)
The most annoying thing about the thousandth of an inch is while it’s often called a ‘thou’, it’s also called a ‘mil’ which sounds exactly as the common slang for millimetre (mill) here in Australia at least (used more often in construction, but it’s still common so makes it confusing). Luckily we don’t really do PCB design in imperial anymore at any of the companies I’ve worked with (I hear even US companies are mov…
The most annoying thing about the thousandth of an inch is while it’s often called a ‘thou’, it’s also called a ‘mil’ which sounds exactly as the common slang for millimetre (mill) here in Australia at least (used more often in construction, but it’s still common so makes it confusing). Luckily we don’t really do PCB design in imperial anymore at any of the companies I’ve worked with (I hear even US companies are mov…
Earlier quoted context omitted.
Why is that? Common components use thous but tooling moved to mils?
My sophisticated wild-ass guess: Film and sheet thicknesses are often specified in mils, and PCBs are essentially fancy sheets of stuff laminated together. My unsophisticated wild-ass guess about why they persevere: Like Fahrenheit, it so happens that mils as a scale intuitively correspond to sizes of trace we care about. A 5 mil trace is pretty run of the mill for signals. 20 mils for most IC supply traces. 3 mils i…
I think the intuition argument is often just a post hoc assumption for things that we are actually just familiar with.
Curious why we jump from 16ths or 32ths to thous rather than 64ths, 128ths, 256ths, 512ths and 1024ths I guess they are a mouthful without good abbreviations and there was a tech jump between woodworking and machining so in betweens aren't used
If a measurement is 3.125 inches, you know that it's 3 inches and 125 mils.
You don't need support for fractional syntax in order to have an input field for inches that goes down to mil precision: just a regular decimal numeric input.
You cannot dismiss the advantage of decimal fractions as casually as you can reject the metric system.
The most annoying thing about the thousandth of an inch is while it’s often called a ‘thou’, it’s also called a ‘mil’ which sounds exactly as the common slang for millimetre (mill) here in Australia at least (used more often in construction, but it’s still common so makes it confusing). Luckily we don’t really do PCB design in imperial anymore at any of the companies I’ve worked with (I hear even US companies are mov…
You're not going to say 20 mil and the context not be clear if you mean 0.508mm or 20mm, are you?
Earlier quoted context omitted.
Why is that? Common components use thous but tooling moved to mils?
My sophisticated wild-ass guess: Film and sheet thicknesses are often specified in mils, and PCBs are essentially fancy sheets of stuff laminated together. My unsophisticated wild-ass guess about why they persevere: Like Fahrenheit, it so happens that mils as a scale intuitively correspond to sizes of trace we care about. A 5 mil trace is pretty run of the mill for signals. 20 mils for most IC supply traces. 3 mils i…
The numbers get even better on the metric system. I was expecting them to just not get much worse, since they were picked on the imperial on.
:o
Curious why we jump from 16ths or 32ths to thous rather than 64ths, 128ths, 256ths, 512ths and 1024ths I guess they are a mouthful without good abbreviations and there was a tech jump between woodworking and machining so in betweens aren't used
Guitar strings are, e.g. 9 to 46: .009" high E, .046" low E.
Classic DIP (dual in-line package) integrated circuits and headers have 100 mil spacing: ten pins per inch. IIRC, you drill a 25 mil hole for the pins. This is international.
The metric system doesn't have a nice mil-like unit for those scales; the millimeter is way too crude, and micrometers are too fine.
The mil is just right for all sorts of miniature things that are still large enough to be worked on by human hands and eyes.
Earlier quoted context omitted.
I think it was all over once America started using ounces to measure volume.
Ounce / fluid ounce is roughly the same as gram / milliliter. A fluid ounce of water weighs about one ounce (1.04 oz/fl oz or something), like a milliliter of water weighs about one gram (0.997 g/mL or something). The US customary units are pretty logical, they're just not powers of 10.
That's how it's used, but the units don't measure the same thing. It's like measuring an engine's power output in square meters, because a kilowatt is about a square meter of sunlight.