I seem to have stepped in it big time here
... A calculater is nice
...... if you're in a class. I prefer to have things where I can convert in my head, a pencil & paper at worst. Ya never know when the batteries will give out. And most times, I don't need an answer to 5 decimal places in imperial. I do use 5 places for a mm because the numbers are easy to remember. Point03937... Pi is 3point14159 Just the way my memory works. I take the measurement of a
...motor shaft with an imperial caliper. If it is 0.079~, it's a 2mm. If it's 0.092+, it's 3/32". In either case, it will work, just a matter of what type of coupling to use. Or what size fuel line. Or whatever I happen to be using for that install.
I have a number of project books, some from the U.S., some from England, and some for pure metrics. Some very old, some recent. The only place I have any trouble is with English fasteners (Whitworth) and pipe fittings. What's called British Standard. But that's just a matter of a different method of measuring. I don't use the English systems very often, so must brush up on them when I have a project from that area. But you've got to watch the English. They started out imperial and converted to metric only recently. Sometimes the systems get a little mixed up. As in both systems side by side. A shaft 2 inches long by 1.5mm diameter. Ya got to think, 2X1/16", more or less. Or 50mmX1.5 if you're trying to stay metric all the way. If the shaft fits into something, can the something be reamed to 1/16. Or is it just to stand off something.
Most metric micrometers read to 25mm, or just a
whisker fuzz under 1.0 inch. Making an imperial leadscrew cut (true)metric threads requires a 127/120 conversion gear. If you backtrack the numbers, the 127 gear is to convert 25.4 to a solid number, one without a
partial remainder. The most important factor is to get comfortable with the idea of a
fuzz and if it's important. A cylinder/piston/rings of any larger size won't matter that much. A shaft, especially a small one, fitting into a bearing, will. It's one of those calls you must make for yourself based on what the book says. The book you have posted is for machine parts. Take a dovetail cross-slide. The angle is important but will be the same, imperial or metric. The width (distance between) may be metric, but a fuzz too full won't really matter because of the gib and setscrews to adjust it. If it calls for 25mm, make it an inch. That's what I was refering to for you to make the call. And the worst case: As a hobbyist, if your call
isn't right, ya make it again, watching the dimensions a little closer.
I'm not trying to denigrate one system under the other here. I'm only trying to give a little insight into the process of making a conversion from one to the other. I responded to a post the other day regarding need vs want. You
need a set of manual calipers and a feeler guage. Anything else is a
want, or time saver. Chew on that for a while.
Bill Hudson