On Monday, December 26, 2011 10:36:04 AM Dave Caroline did opine:

> The tool cutting brass is one I found amongst some cutters at a clock
> and watch show
> It just suited the job, you can also use commercial thread mills
> eg
> http://www.kennametal.com/en-US/products_services/metalworking/tapping/t
> hread_mills/thread_mills_products.jhtml
> 
These of course have to be ordered per tpi, and Kennametal has any pricing 
hidden behind a login screen.  Bad dog they be, no biscuit from me.

> While designed for steel but have a limited range as designed not for
> tilting to the correct thread angle
> so will produce a concave shape to the thread form if out of design
> range (I dont know the maths to show the effect)
> but my first attempt did show the error as the tool is large in
> diameter compared to thread angle
> 
> note this code lacks sensible centerline finding and b axis angle
> although #4 is the value it should be based on
> and reviewing it some comments are a bit off :)
> 
> e&oe
> 
> (metric worm cnc prog)
> (cnc preamble)
> G20 (set inches)
> G64 (?)
> G90 (set absolute)
> G94 (set inches per min)
> #<number_of_starts>=1   (#9  number of starts)
> (for mod worm calc DP for it)
> 
> #<DP>=25 (#10 DP of system)
> #<teeth>=60
> #<pcd_wheel>=[#<teeth>/#<DP>]     (d ebug, pcd of wheel #14)
> #<pcd_worm>=[[1.25-[#<pcd_wheel>/2]]*2]    (de bug, worm pitch dia df
> #<pcd_worm>)
> #<n_turns>= 6             (#11 number of turns in worm)
> #<rotation_angle>=[360 * #<n_turns>]  (#1 set rotation degrees)
> 
> #<m>=[1/#<DP>]           (#6 m imperial module)
> 
> 
> #<df>=[#<pcd_worm> / #<m>] (deb ug,q diameter factor #<df>)
> #<df_od>=[4 / #<m>] (de bug,q diameter factor #<df_od>)
> 
> #7=[3.14159625*#<number_of_starts> * #<m>] (D EBUG,Lead =pi*1*#<m> L=#7
> ) #8=[#<number_of_starts>/#<df>]
> #9=[#<number_of_starts>/#<df_od>]
> #2=[atan[#8]/[1] ]     (debug,angle of helix #2 angle to rotate
> trunnion from vertical when I get one!!)
> #<tp_angle>=[atan[#9]/[1] ]     (deb ug,angle of helix to rotate ar
> tip #<tp_angle>)
> #3=[#<n_turns>*#7]     (DEB UG,length of cut #3)
> #4=[sin[#2] * #3]      (DE BUG,y=#4 offset to move to track worm
> centerline) #5=[cos[#2] * #3]      (DE BUG,shortened Z=#5 because
> tilted)
> #20=[#4]               (D EBUB,corrected direction y offset #20)
> G0 X0 Y0 Z0 (move cutter centerline lowest point in line with axis and
> touch off)
> G0 F1 A-5 (rotate blank back to start+1)
> G0 F1 A0 (rotate blank to draw center line)
> 
> G1 F.1 X-.063 Y0 Z0 A0 (move cutter to depth)
> G1 F.05 x-.063 Y[0-#20] Z[0-#5] A[0-#<rotation_angle>] (rotate blank 7
> turns)
> 
> G1 F1 X0 Y[0-#20] Z[0-#5] A[0-#<rotation_angle>] (move cutter out)
> 
> (G10 L2 P1 A0)
> 
> (G92 A-2520)
> G0 A0 (rotate blank back to start)
> G0 X0 Y0 Z0
> 
> 
> if email buggers the above see
> http://www.archivist.info/cnc/worm2.ngc
> 
Will do, thanks.
> 
> Dave Caroline
> 
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Cheers, Gene
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
My web page: <http://coyoteden.dyndns-free.com:85/gene>
  Goes (Went) over like a lead balloon.

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http://p.sf.net/sfu/intel-appdev
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