Re: [Emc-users] Tapered Helix

[Gene Heskett]

On Wednesday 21 March 2018 15:36:23 Ken Strauss wrote:

> That is a little too large! My current need is to make some tapered
> external threads for photographic cable releases: 28-degree included
> angle, 0.5mm pitch, 3.75mm at the big end.

This mill I have, would do that just fine since its an external thread.

However, those threads are relatively coarse considering the od. And 
since the taper angle is in essence limited by the pitch of the thread, 
and those things are rarely over 1/4" long, the 28 degree angle should 
be easily done.  And for that I wouldn't hesitate to use a g76, and a 
threading tool in a vice, with the end terminal for the cable in a 
suitable collet (sp?) in the spindle of a mill. Or, since the tool is or 
can be moved by the x axis, and the cable release is in the z, a g76 
with a long e l2 would do it just fine. Run the spindle in reverse with 
the tool reversed too and a z-3/16 or so, so the entry is at the top and 
the small end of the taper is on the bottom. G76 can do more than the 
man page talks about, just figure on cutting a couple buckets of air 
getting exactly what you want. ;-) Precutting the taper might be a good 
idea.


See the g76, and how its invoked, in the code I did post, last cut at the 
bottom of that file.
-- 
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Tapered Helix

[Kirk Wallace]

On 03/21/2018 07:47 AM, Ken Strauss wrote:

I need to thread mill some tapered threads (similar to normal pipe threads --
NPT). I am considering using polar coordinates in incremental mode to
approximate a tapered helix. Is that reasonable? Is there a better way? Will
cumulative errors bite me after hundreds of incremental moves?


It has been a while since I looked at this sort of thing, but off-hand I 
think the G2/3 code is able to do a tapered helix with the proper 
parameter settings:

http://linuxcnc.org/docs/2.7/html/gcode/g-code.html#gcode:g2-g3


The current location is the start XYZ position of the helical thread 
mill path (allow for lead-in and out, if needed). The XYZ parameters set 
the path end location. The XY values set the end of the path which 
should have the taper included. The Z and P set the thread length and 
number of turns. I seem to recall having to calculate the last bit of an 
additional arc to finish the thread if it doesn't end in a full turn. I 
also seem to recall that P and the real number of turns is not 
intuitive, so cut air until you get what you need. I may be all wet on 
the above so check out the documentation and test for yourself. There 
are a lot of features and calculations between the control point path 
and the thread form -- tool diameter, tip truncation, thread pitch cone 
dimensions, etcetera.


Or not.

--
Kirk Wallace
http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/

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Re: [Emc-users] Tapered Helix

[Ken Strauss]

That is a little too large! My current need is to make some tapered external
threads for photographic cable releases: 28-degree included angle, 0.5mm
pitch, 3.75mm at the big end.

> -Original Message-
> From: Gene Heskett [mailto:ghesk...@shentel.net]
> Sent: Wednesday, March 21, 2018 3:00 PM
> To: emc-users@lists.sourceforge.net
> Subject: Re: [Emc-users] Tapered Helix
>
> On Wednesday 21 March 2018 14:38:09 Ken Strauss wrote:
>
> > Thanks but...
> > Isn't G76 for threading on a lathe and G33.1 for rigid tapping? I'm
> > doing thread milling.
> >
> G76 is istr limited to lathe's as its not subject to the g17-19 rules.
>
> G33.1 can function on any axis set of a mill. So it might be modifyable
for your
> use. I've used it for rigid tapping with the head laid horizontal on my
G0704.
> Worked well.
>
> Andy's code looks much simpler, so I would first see if it could do what
you
> need to do.
>
> I only have one thread mill, .750" OD and its likely too big, or almost
too big
> for a 1" pipe thread.
>
>
> > > -Original Message-
> > > From: Gene Heskett [mailto:ghesk...@shentel.net]
> > > Sent: Wednesday, March 21, 2018 2:07 PM
> > > To: emc-users@lists.sourceforge.net
> > > Subject: Re: [Emc-users] Tapered Helix
> > >
> > > On Wednesday 21 March 2018 10:47:31 Ken Strauss wrote:
> > > > I need to thread mill some tapered threads (similar to normal pipe
> > > > threads -- NPT). I am considering using polar coordinates in
> > > > incremental mode to approximate a tapered helix. Is that
> > > > reasonable? Is there a better way? Will cumulative errors bite me
> > > > after hundreds of incremental moves?
> > >
> > > How big, Ken? Inside I assume... I have used both the G76 and G33.1
> > > for
> >
> > low
> >
> > > angle stuffs by setting the entrance or exit paper length to
> > > 1 pitch less than the length of the thread.  The man page is wrong
> > > when
> >
> > says
> >
> > > the taper limit is 1/2 the thread length. I think that could be
> > > extended
> >
> > by
> >
> > > doing the first using that rule of one pitch less than the total
> > > stroke,
> >
> > and if
> >
> > > thats not deep enough, advance the z a multiple of the pitch, I've
> > > not
> >
> > proved
> >
> > > it, might need some adjusting, and reduce the starting r by the
> > > height difference used in the first pass.
> > >
> > > I have used this code to make a socket in the end of a shaft, that
> > > with a matching taper threaded nut, and making 4 petals out of the
> > > walls with
> >
> > edm,
> >
> > > to compress an A2 shaft onto a smallish ball screw, by tightening
> > > the nut.
> >
> > Its
> >
> > > driving the x axis of my Sheldon 11x36 right now. With some green
> > > threadlocker in the socket, I don't expect it to slip until I loosen
> > > the
> >
> > nut.
> >
> > > Here is that file, quite complex because I tend to make a one trip
> >
> > Bumstead
> >
> > > out of projects like this, so it can be switched from boreing to
> > > turning
> >
> > yadda
> >
> > > yadda.
> > >
> > > Setup ATM for making the nut described above. load it into LinuxCNC,
> > > and expand the backplot to get a good view of what it does.  Reading
> > > the code
> >
> > will
> >
> > > show you where and what to modify for your project, if its usable at
> > > all. ===cut here>
> > > %
> > > ( this is to make use of the g33 routine to carve a thread in the
> > > format )
> >
> > ( of a
> >
> > > pipe thread, in this case an odd size that would resemble a 3/16" )
> > > ( pipe thread is indeed there ever was such a thing. :) ( because
> > > that seems to
> >
> > be a
> >
> > > Merican only thing, all starting dimensions are in inch) ( there is
> > > a BS
> >
> > spec,
> >
> > > looks a lot like ASTME to me :) ( since everything is converted to
> > > metric
> >
> > below,
> >
> > > make sure its in metric mode) ( We start not with a Merican
> > > fractonal, but
> >
> > at
> >
> > > any arbitrary size ) ( and tpi, and degrees of taper desired if
> > > desire

Re: [Emc-users] Tapered Helix

[Gene Heskett]

On Wednesday 21 March 2018 14:38:09 Ken Strauss wrote:

> Thanks but...
> Isn't G76 for threading on a lathe and G33.1 for rigid tapping? I'm
> doing thread milling.
>
G76 is istr limited to lathe's as its not subject to the g17-19 rules. 

G33.1 can function on any axis set of a mill. So it might be modifyable 
for your use. I've used it for rigid tapping with the head laid 
horizontal on my G0704. Worked well.

Andy's code looks much simpler, so I would first see if it could do what 
you need to do.

I only have one thread mill, .750" OD and its likely too big, or almost 
too big for a 1" pipe thread.


> > -Original Message-
> > From: Gene Heskett [mailto:ghesk...@shentel.net]
> > Sent: Wednesday, March 21, 2018 2:07 PM
> > To: emc-users@lists.sourceforge.net
> > Subject: Re: [Emc-users] Tapered Helix
> >
> > On Wednesday 21 March 2018 10:47:31 Ken Strauss wrote:
> > > I need to thread mill some tapered threads (similar to normal pipe
> > > threads -- NPT). I am considering using polar coordinates in
> > > incremental mode to approximate a tapered helix. Is that
> > > reasonable? Is there a better way? Will cumulative errors bite me
> > > after hundreds of incremental moves?
> >
> > How big, Ken? Inside I assume... I have used both the G76 and G33.1
> > for
>
> low
>
> > angle stuffs by setting the entrance or exit paper length to
> > 1 pitch less than the length of the thread.  The man page is wrong
> > when
>
> says
>
> > the taper limit is 1/2 the thread length. I think that could be
> > extended
>
> by
>
> > doing the first using that rule of one pitch less than the total
> > stroke,
>
> and if
>
> > thats not deep enough, advance the z a multiple of the pitch, I've
> > not
>
> proved
>
> > it, might need some adjusting, and reduce the starting r by the
> > height difference used in the first pass.
> >
> > I have used this code to make a socket in the end of a shaft, that
> > with a matching taper threaded nut, and making 4 petals out of the
> > walls with
>
> edm,
>
> > to compress an A2 shaft onto a smallish ball screw, by tightening
> > the nut.
>
> Its
>
> > driving the x axis of my Sheldon 11x36 right now. With some green
> > threadlocker in the socket, I don't expect it to slip until I loosen
> > the
>
> nut.
>
> > Here is that file, quite complex because I tend to make a one trip
>
> Bumstead
>
> > out of projects like this, so it can be switched from boreing to
> > turning
>
> yadda
>
> > yadda.
> >
> > Setup ATM for making the nut described above. load it into LinuxCNC,
> > and expand the backplot to get a good view of what it does.  Reading
> > the code
>
> will
>
> > show you where and what to modify for your project, if its usable at
> > all. ===cut here>
> > %
> > ( this is to make use of the g33 routine to carve a thread in the
> > format )
>
> ( of a
>
> > pipe thread, in this case an odd size that would resemble a 3/16" )
> > ( pipe thread is indeed there ever was such a thing. :) ( because
> > that seems to
>
> be a
>
> > Merican only thing, all starting dimensions are in inch) ( there is
> > a BS
>
> spec,
>
> > looks a lot like ASTME to me :) ( since everything is converted to
> > metric
>
> below,
>
> > make sure its in metric mode) ( We start not with a Merican
> > fractonal, but
>
> at
>
> > any arbitrary size ) ( and tpi, and degrees of taper desired if
> > desired. )
>
> ( length
>
> > of taper will be based on the thickness of the nut, which will
> > determine )
>
> (
>
> > that the stated angle will be true for the length of the nut ) (
> > however,
>
> the
>
> > actual Z travel will be longer since the initial Z should be a ) (
> > couple
>
> mm's
>
> > from first contact.)
> > (logopen,/home/gene/linuxcnc/g33debug.txt)
> > G21 (metric)
> > G8 (lathe radius mode)
> > G61
> > S350
> > ( set straight, like g76 by bypassing the G33 stuff)
> > #<_do_taper>= 0.00
> > #<_taper_deg>   = 7 ( degrees here, translates to sin[7]  later)
> > #<_bore_turn>   = 0. ( 1 for bore, zero for an
>
> external
>
> > profile)
> > #<_input_is_inch>   = 1. ( zero for all metric inputs)
> > #<_tpi> =   50 (adjustable. If input is i

Re: [Emc-users] Tapered Helix

[Ken Strauss]

Thanks but...
Isn't G76 for threading on a lathe and G33.1 for rigid tapping? I'm doing
thread milling.

> -Original Message-
> From: Gene Heskett [mailto:ghesk...@shentel.net]
> Sent: Wednesday, March 21, 2018 2:07 PM
> To: emc-users@lists.sourceforge.net
> Subject: Re: [Emc-users] Tapered Helix
>
> On Wednesday 21 March 2018 10:47:31 Ken Strauss wrote:
>
> > I need to thread mill some tapered threads (similar to normal pipe
> > threads -- NPT). I am considering using polar coordinates in
> > incremental mode to approximate a tapered helix. Is that reasonable?
> > Is there a better way? Will cumulative errors bite me after hundreds
> > of incremental moves?
> >
> How big, Ken? Inside I assume... I have used both the G76 and G33.1 for
low
> angle stuffs by setting the entrance or exit paper length to
> 1 pitch less than the length of the thread.  The man page is wrong when
says
> the taper limit is 1/2 the thread length. I think that could be extended
by
> doing the first using that rule of one pitch less than the total stroke,
and if
> thats not deep enough, advance the z a multiple of the pitch, I've not
proved
> it, might need some adjusting, and reduce the starting r by the height
> difference used in the first pass.
>
> I have used this code to make a socket in the end of a shaft, that with a
> matching taper threaded nut, and making 4 petals out of the walls with
edm,
> to compress an A2 shaft onto a smallish ball screw, by tightening the nut.
Its
> driving the x axis of my Sheldon 11x36 right now. With some green
> threadlocker in the socket, I don't expect it to slip until I loosen the
nut.
>
> Here is that file, quite complex because I tend to make a one trip
Bumstead
> out of projects like this, so it can be switched from boreing to turning
yadda
> yadda.
>
> Setup ATM for making the nut described above. load it into LinuxCNC, and
> expand the backplot to get a good view of what it does.  Reading the code
will
> show you where and what to modify for your project, if its usable at all.
> ===cut here>
> %
> ( this is to make use of the g33 routine to carve a thread in the format )
( of a
> pipe thread, in this case an odd size that would resemble a 3/16" ) ( pipe
> thread is indeed there ever was such a thing. :) ( because that seems to
be a
> Merican only thing, all starting dimensions are in inch) ( there is a BS
spec,
> looks a lot like ASTME to me :) ( since everything is converted to metric
below,
> make sure its in metric mode) ( We start not with a Merican fractonal, but
at
> any arbitrary size ) ( and tpi, and degrees of taper desired if desired. )
( length
> of taper will be based on the thickness of the nut, which will determine )
(
> that the stated angle will be true for the length of the nut ) ( however,
the
> actual Z travel will be longer since the initial Z should be a ) ( couple
mm's
> from first contact.)
> (logopen,/home/gene/linuxcnc/g33debug.txt)
> G21 (metric)
> G8 (lathe radius mode)
> G61
> S350
> ( set straight, like g76 by bypassing the G33 stuff)
> #<_do_taper>  = 0.00
> #<_taper_deg> = 7 ( degrees here, translates to sin[7]  later)
> #<_bore_turn> = 0. ( 1 for bore, zero for an
external
> profile)
> #<_input_is_inch> = 1. ( zero for all metric inputs)
> #<_tpi>   =   50 (adjustable. If input is inches,
use inch, else
> PUT mm's here)
> #<_mkmmfctr>  =   25.4 (inch <-> metric conversion)
> ( constants from Cecils images )
> #<_e_xz_fctr> =   0.708200 ( external -x +z combined feed
> factor)
> #<_e_doc_fctr>=   0.613400 ( external thread
d.o.c. external
> cuts deeper)
> #<_i_xz_fctr> =   0.625000 ( internal +x +z combined feed
> factor)
> #<_i_doc_fctr>=   0.542700 ( internal thread
d.o.c. internal
> is shallower)
> (edit these)
> #<_start_OD>  =   0.7550 ( this is inches at the min/max
OD
> of thread it fits)
> #<_thread_len>=   0.5600 (is inches, thickness of
nut I
> started with )
> #<_passes>= 25. (easy on the tool, constant advance)
> #<_spring_passes> = 5.
>
>
> (z advance derived from Cecils images IS NOT 100% CORRECT YET)
> #<_e_z_advance>   = [[#<_e_xz_fctr> - #<_e_doc_fctr>] /
#<_passes>]
> #<_i_z_advance>   = [[#<_i_xz_fctr> - #<_i_doc_fctr>] /
#<_passes>]
> (log,38 e z advance per pass=#<_e_z_advance>)
> (lo

Re: [Emc-users] Tapered Helix

[Gene Heskett]

On Wednesday 21 March 2018 10:47:31 Ken Strauss wrote:

> I need to thread mill some tapered threads (similar to normal pipe
> threads -- NPT). I am considering using polar coordinates in
> incremental mode to approximate a tapered helix. Is that reasonable?
> Is there a better way? Will cumulative errors bite me after hundreds
> of incremental moves?
>
How big, Ken? Inside I assume... I have used both the G76 and G33.1 
for low angle stuffs by setting the entrance or exit paper length to 
1 pitch less than the length of the thread.  The man page is wrong when 
says the taper limit is 1/2 the thread length. I think that could be 
extended by doing the first using that rule of one pitch less than the total 
stroke, and if thats not deep enough, advance the z a multiple of the pitch,
I've not proved it, might need some adjusting, and reduce the starting r 
by the height difference used in the first pass.

I have used this code to make a socket in the end of a shaft, that with a 
matching taper threaded nut, and making 4 petals out of the walls with 
edm, to compress an A2 shaft onto a smallish ball screw, by tightening 
the nut. Its driving the x axis of my Sheldon 11x36 right now. With some 
green threadlocker in the socket, I don't expect it to slip until I 
loosen the nut.

Here is that file, quite complex because I tend to make a one trip 
Bumstead out of projects like this, so it can be switched from boreing 
to turning yadda yadda.

Setup ATM for making the nut described above. load it into LinuxCNC, 
and expand the backplot to get a good view of what it does.  Reading 
the code will show you where and what to modify for your project, if
its usable at all.
===cut here>
%
( this is to make use of the g33 routine to carve a thread in the format )
( of a pipe thread, in this case an odd size that would resemble a 3/16" )
( pipe thread is indeed there ever was such a thing. :)
( because that seems to be a Merican only thing, all starting dimensions are in 
inch)
( there is a BS spec, looks a lot like ASTME to me :)
( since everything is converted to metric below, make sure its in metric mode)
( We start not with a Merican fractonal, but at any arbitrary size )
( and tpi, and degrees of taper desired if desired. )
( length of taper will be based on the thickness of the nut, which will 
determine )
( that the stated angle will be true for the length of the nut )
( however, the actual Z travel will be longer since the initial Z should be a )
( couple mm's from first contact.)
(logopen,/home/gene/linuxcnc/g33debug.txt)
G21 (metric)
G8 (lathe radius mode)
G61
S350
( set straight, like g76 by bypassing the G33 stuff)
#<_do_taper>= 0.00
#<_taper_deg>   = 7 ( degrees here, translates to sin[7]  later)
#<_bore_turn>   = 0. ( 1 for bore, zero for an external profile)
#<_input_is_inch>   = 1. ( zero for all metric inputs)
#<_tpi> =   50 (adjustable. If input is inches, use inch, 
else PUT mm's here)
#<_mkmmfctr>=   25.4 (inch <-> metric conversion)
( constants from Cecils images )
#<_e_xz_fctr>   =   0.708200 ( external -x +z combined feed 
factor)
#<_e_doc_fctr>  =   0.613400 ( external thread d.o.c. external 
cuts deeper)
#<_i_xz_fctr>   =   0.625000 ( internal +x +z combined feed 
factor)
#<_i_doc_fctr>  =   0.542700 ( internal thread d.o.c. internal 
is shallower)
(edit these)
#<_start_OD>=   0.7550 ( this is inches at the min/max OD 
of thread it fits)
#<_thread_len>  =   0.5600 (is inches, thickness of nut I 
started with )
#<_passes>  = 25. (easy on the tool, constant advance)
#<_spring_passes>   = 5.


(z advance derived from Cecils images IS NOT 100% CORRECT YET)
#<_e_z_advance> = [[#<_e_xz_fctr> - #<_e_doc_fctr>] / #<_passes>]
#<_i_z_advance> = [[#<_i_xz_fctr> - #<_i_doc_fctr>] / #<_passes>]
(log,38 e z advance per pass=#<_e_z_advance>)
(log,39 i z advance per pass=#<_i_z_advance>)
( now the x increments)
#<_e_x_advance> = [#<_e_doc_fctr> / #<_passes>]
#<_i_x_advance> = [#<_i_doc_fctr> / #<_passes>]
(log,43 e x advance per pass=#<_e_x_advance>)
(log,44 i x advance per pass=#<_i_x_advance>)
( these figures s/b very small )

o005 IF [#<_input_is_inch> gt 0.5000]

#<_tpmm>= [#<_mkmmfctr> / #<_tpi>] (mm's! - is correct )
#<_start_OD>= [#<_start_OD> * 0.500 * #<_mkmmfctr>]
#<_thread_len>  = [#<_thread_len> * #<_mkmmfctr>]

o005 ELSE

#<_tpmm>= #<_tpi>

o005 ENDIF
(log,57 tpmm=#<_tpmm>)
(log,58 start OD in mm=#<_start_OD>)
(log,59 thread length in mm=#<_thread_len>)

( now we have the Major radius start_OD that everything else references one way 
or another )
#<_e_x_mnr_R>   =   [#<_start_OD> + [#<_e_doc_fctr> * #<_tpmm>]] ( 
final d.o.c. )
#<_e_x_mjr_R>   =   [#<_sta

Re: [Emc-users] Tapered Helix

[andy pugh]

On 21 March 2018 at 17:39, Ken Strauss  wrote:
> Thanks for the suggestions but I'm confused. Does G1 in polar coordinates
> produce an arc or a straight line?

I don't know :-) (I was miles away from my LinuxCNC machines when I wrote that)

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] Tapered Helix

[Ken Strauss]

Thanks for the suggestions but I'm confused. Does G1 in polar coordinates 
produce an arc or a straight line?

> -Original Message-
> From: andy pugh [mailto:bodge...@gmail.com]
> Sent: Wednesday, March 21, 2018 11:49 AM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] Tapered Helix
>
> On 21 March 2018 at 14:47, Ken Strauss  wrote:
> > I need to thread mill some tapered threads (similar to normal pipe
> > threads -- NPT). I am considering using polar coordinates in
> > incremental mode to approximate a tapered helix. Is that reasonable?
> > Is there a better way? Will cumulative errors bite me after hundreds of
> incremental moves?
>
> Why use incremental mode? It is probably just as easy to use variables and a
> loop
>
> Polar coordinates ought to work, but you can approximate a spiral with arcs
> too. (I would guess that 8 per rev would be better than 4 per
> rev)
>
> In polar, and not using incremental, something like this, assuming you are
> already at X0 Y0
>
> # = -1
> # = [1 / 13] ; 13TPI
> # = [1 / 2] ; radius of 1" thread
> F10
> G0 Z #
> G1 ^0 @#
> O100 DO
> G1 ^90 @[# + # /64]  Z[# + # * 0.25]
> G1 ^180 @[# + # / 32]  Z[# + # * 0.5]
> G1 ^ 270 @[# + # / 21.33]  Z[# + # * 0.75]
> G1 ^ 360 @[# + # / 16]  Z[# + # * 1.0]
> # = [# + #]
> O100 WHILE [# LT #]
>
> This uses 4 arcs. It could be done exactly the same with more, for a closer
> approximation to a true spiral.
>
> --
> atp
> "A motorcycle is a bicycle with a pandemonium attachment and is designed
> for the especial use of mechanical geniuses, daredevils and lunatics."
> - George Fitch, Atlanta Constitution Newspaper, 1916
>
> --
> Check out the vibrant tech community on one of the world's most engaging
> tech sites, Slashdot.org! http://sdm.link/slashdot
> ___
> Emc-users mailing list
> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users



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Re: [Emc-users] Tapered Helix

[andy pugh]

On 21 March 2018 at 14:47, Ken Strauss  wrote:
> I need to thread mill some tapered threads (similar to normal pipe threads --
> NPT). I am considering using polar coordinates in incremental mode to
> approximate a tapered helix. Is that reasonable? Is there a better way? Will
> cumulative errors bite me after hundreds of incremental moves?

Why use incremental mode? It is probably just as easy to use variables
and a loop

Polar coordinates ought to work, but you can approximate a spiral with
arcs too. (I would guess that 8 per rev would be better than 4 per
rev)

In polar, and not using incremental, something like this, assuming you
are already at X0 Y0

# = -1
# = [1 / 13] ; 13TPI
# = [1 / 2] ; radius of 1" thread
F10
G0 Z #
G1 ^0 @#
O100 DO
G1 ^90 @[# + # /64]  Z[# + # * 0.25]
G1 ^180 @[# + # / 32]  Z[# + # * 0.5]
G1 ^ 270 @[# + # / 21.33]  Z[# + # * 0.75]
G1 ^ 360 @[# + # / 16]  Z[# + # * 1.0]
# = [# + #]
O100 WHILE [# LT #]

This uses 4 arcs. It could be done exactly the same with more, for a
closer approximation to a true spiral.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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[Emc-users] Tapered Helix

[Ken Strauss]

I need to thread mill some tapered threads (similar to normal pipe threads --  
NPT). I am considering using polar coordinates in incremental mode to 
approximate a tapered helix. Is that reasonable? Is there a better way? Will 
cumulative errors bite me after hundreds of incremental moves?



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