The recent discussion of hub and BB standards appeared to ignore the fact
that ANY machine dimension has a tolerance and an allowance between itself
and the mating part, (as between a bolt and a nut). allowance, whether
stated or not. That's why there are different grades of the same bolts in a
good hardware store. The cheaper grades are made for a relatively sloppy
fit, and the expensive grades may have a tighter "class" of fit. The
tolerance is the set of dimensional limits, (someone mentioned 1.370 and
1.375). The 1.375 is PROBABLY the upper limit, and the part is still within
the standard id it is five thousandths smaller (1.370). Obviously, the
largest possible diameter for the male part must be smaller than the
smallest possible diameter for the female part, so when we talk ablut a "one
and three-eighths diameter hub-to-freewheel thread, that is a NOMINAL
dimension, rather than something a machinist would work to. You can be sure
that the drawings the manufacturer uses have a tolerance or a pair of limit
dimensions for every diameter that has to mate with something else. (Many
of you will already know all this, but those who toil outside the
manufacturing fraternity may not.)
As for scrubbing chrome, has anyone tried #M scouring pads? I recently
found that 3M, ( who make sandpaper and Scotch tape products) are now
marketing versions of these kitchen pads in equivalent sandpaper grades.
Chris Andrews in Sequim, WA