On Fri, 22 Apr 2005 20:53:42 GMT,
(Marvin W. Klotz) wrote:

On Fri, 22 Apr 2005 20:47:42 GMT, "William Graves"
wrote:

If you place a plate of thickness, t, between one jaw of a 3-jaw chuck and
now bore a hole,
what is the offset of that hole from the center of the original rod
(diameter, D).

One source says it is 2/3 of t. This might be = 1 / (1 + cos 60 deg) but I
failed to derive this with trig.

Anyone know how to derive this mathematically?
Anyone know if this is true?

thanks
-- - - - - - - - - - - - - - - - -
Bill Graves RKBA!



The formula is a good bit more complicated than that. Take a look at the
ECCENT.ZIP archive on my website for a program that implements the correct
formula.

Regards, Marv

Home Shop Freeware - Tools for People Who Build Things
http://www.geocities.com/mklotz.geo


A really excellent set of useful utilities!

One question on the ECCENT program.

This needs accurate knowledge of the width of
w - the little flat part at the end of the jaw that
contacts the workpiece. This is fiendishly difficult to
directly measure accurately. Your program has an elegant way
of avoiding this problem by making the spacer in the form of
a slotted tube.

However it's not always convenient to find or
fabricate a suitable tube. I think that an alternative
possibility is to simply find the largest size drill rod
that will enter the fully closed jaws of the three jaw
chuck. The effective jaw width w would then be accurately
defined by the sides of the equilateral triangle that
circumscribes that drill rod size.

Is this a reasonable approach and could it be
incorporated in your program?

Jim