[CR]Chrome polishing and thread standards


Example: Framebuilders
Date: Mon, 04 Feb 2002 15:12:05 -0800
From: "Chris Andrews" <andrews@tenforward.com>
To: classicrendezvous@bikelist.org
Subject: [CR]Chrome polishing and thread standards

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