[SEL] Introducing........

[Jim Kirkes]

OK here is how it is done, machine accurate angles, amaze 
your friends and earn big bucks.

If you have a protractor scribe the angle you want about 
where the top of the vise jaws will be when you machine the 
part.  Put the part in the vise and
pinch it on the scribe line.  Tighten the vise so that you 
can still move the part with a soft hammer.  If you have 
done this fairly accurately it helps to set one end (doesn't 
matter which) slightly high so you know which why it will 
need to move to be on the nut.

Now get out your trig tables and look up the tangent of the 
angle you want to machine.  In Eldon's case  .1989 for 11 
deg 15 minutes.  Now put your indicator on the head of the 
mill.  I prefer a drill chuck but any way it is solid will 
work.  Use an indicator that read in  .001 increments.  Now 
contact the indicator to the work and adjust it till reads 
zero.  Drop the knee an amount equal to the tangent or .199 
(rounded off here) without touching the indicator
move 1 inch.  If the indicator reads zero you have the 
angle, if it doesn't tap it slightly to correct the position 
and repeat the process until it reads zero for
both ends.  The accuracy can be enhanced by working the 
baseline over a longer distance.  For instance if you use 3 
inches the tangent will have to multiplied by 3.

If this is done with care you can easily machine an angle to 
several minutes of arc provided there is an accurate surface 
to reference to.

Jim and Diane Kirkes
Hemet, California U.S.A.
jd.kirkes at verizon.net>