Subject: How to cut a rack?

From: [email-masked] (Joe Landau)
Date: Sun, 28 Jan 96 19:21:29 GMT

I have an old machine (a Barnes lathe) with a carriage rack with some broken
teeth.  I thought I'd make a new one on my vertical mill, but looking in MSC I 
see no end mills for cutting gear teeth, only horizontal cutters.  

Any suggestions?  sources?  make an end mill with the right form?  Sounds 
hard.  Also, can anyone suggest a good way to identify the pressure angle?  

--
Joseph R. Landau                                 [email-masked]
Applied Software Technology                          (408)370-2662
591 W. Hamilton Ave., #201
Campbell, CA 95008  USA                             Even Jove Nods

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From: David W Hoskin <[email-masked]>
Date: Mon, 29 Jan 1996 11:44:08 +0000

In article <[email-masked]>, "Jonathan M. Elson"
<[email-masked]> writes
>
>You will need to get a fairly large diameter gear tooth mill, to clear the
>bulky main spindle casting of the machine.  Set it up and measure the 
>clearance under the head to see how big a mill you need.  This may be a real
>problem, many gear tooth mills are of small diameter. 
>
How about tilting the head to 90 deg., mounting a disc of sufficient
diameter to clear the head casting (a faceplate?) and setting a home-
made form tool on the circumference to produce a single point flycutter.

--                    **************************************************
Regards,              The business of finding fault is very easy: that
David Hoskin          of doing better, very difficult.(Francis de Sales)
East Yorkshire, UK    **************************************************

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From: [email-masked] (Jonathan M. Elson)
Date: 29 Jan 1996 07:00:36 GMT

Joe Landau ([email-masked]) wrote:
: I have an old machine (a Barnes lathe) with a carriage rack with some broken
: teeth.  I thought I'd make a new one on my vertical mill, but looking in MSC I 
: see no end mills for cutting gear teeth, only horizontal cutters.  

: Any suggestions?  sources?  make an end mill with the right form?  Sounds 
: hard.  Also, can anyone suggest a good way to identify the pressure angle?  

Well, to turn a vertical mill into a horizontal, you just tilt the head over
90 degrees.  This , of course, means that the rack would be laid left/right,
not like on a regular horizontal mill.  But that is better to use the longest
table axis for the rack.

You will need to get a fairly large diameter gear tooth mill, to clear the
bulky main spindle casting of the machine.  Set it up and measure the 
clearance under the head to see how big a mill you need.  This may be a real
problem, many gear tooth mills are of small diameter.  Hmmm, an idea is 
forming.  Use a narrow side milling cutter, or even a slitting saw - tilt the
head close to 90 degrees, but with spindle down and motor up, 90 degrees
minus pressure angle!  (Or would that be 90 degrees minus 1/2 PA?)  Anyway,
use the mill to cut narrow, tilted grooves one way, then reverse the rack
(or head tilt) and repeat the process.  You now have approximated gear teeth!
This should work very nicely for the 20 degree profile, but the 14 1/2 degree
profile has a more complex curve to it, and requires a formed cutter.
Well, it's an idea, anyway.