On 2009-12-01, Joseph Gwinn wrote:
In article
,
whit3rd wrote:

On Nov 25, 12:56*pm, Joseph Gwinn wrote:

The sizes will not be arbitrarily chosen, as there is money at stake. *

Correct.

The problem being solved is how to choose diameters such that the fewest
number of sizes will cover the needed range.

Maybe not; the original of the drill gage is a wire gage, and the
wire-drawing process is more likely the driving technology, not
the drill requirement.

Maybe yes. It may be that the rule for number drills was driven by the
rule for drawing wire, but there nonetheless is a rule.

But the number sizes were tweaked a bit to avoid duplicating
fractional sizes, so there are more fine steps available for a complete
set of drill bits. (The letter sizes have an exception -- isn't it 'F'
which is precisely 1/4"?) For even more fine steps, get a set of metric
bits in 0.1mm steps to keep with your fractional/number/letter set.

BTW -- How many of you have one of the 115 bit HUOT indexes which hold
fractional, letter, and number sizes? How many of you have
wondered what the little bent-up hook is for in the letter size
section?

Well ... it is just right to hold a HUOT index for #61-#80 wire
sized bits, so I have just exactly that in mine. Presumably
somewhere it is documented that this is what it is for, but if
so, I haven't seen it yet. :-)

Enjoy,
DoN.

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