My guy asked me to cut a 1mm pitch thread on a custom shaft.
I could not do it on my lathe, so I finally bit the bullet and wrote a
subroutine to do threading with my 4th axis rotary table. I use a 60
degree chamfering end mill.
Now I can cut any thread, any pitch, right or left handed, and if the
thread is very coarse, the subroutine does it in several passes.
formatting link
I am afraid that it does not create a 100% correct thread geometry,
but I hope that I can do enough things with it to be useful with some
adjustments to diameter.
i
And here's the subroutine, released under GPL v3
(Makes a thread on a round part rotated in my fourth axis)
(Uses a 60 degree end mill)
O sub
# = #1 (X0, left side)
# = #2 (X1, right side)
# = #3 (Y, middle of the top edge of the round)
# = #4 (Z, top of the edge of the round)
# = #5 (Safe Z for rapids)
# = #6 (Z Step, positive)
# = #7 (Step Per Revolution, Also determines Total Depth)
# = #8 (Depth of thread, positive, determined automatically if 0
based on 60 degree thread.)
# = #9 (Diameter of the round, needed for calculations of feed
rate)
# = #10 (feed rate based on surface speed)
# = #11 (Set to 1 if left handed)
# = [#/3.1415/#]
# = [#*#]
# = [#/5]
# = [ 360 * [#-#]/# ]
(Set negative total angle if left handed thread)
O if [# NE 0]
# = [-#]
O endif
O if [# EQ 0]
;# = [#*1.73205/2] (depth = spr * sqrt 3 / 2 )
;
formatting link
# = [#*0.64952] (depth = spr * sqrt 3 / 2 )
O endif
O call [#]
G0 A0 (go to 0 degree)
G0 X[#] Y[#] Z[#]
( Start drilling down to Z0, I could rapid, )
( but slow is safer, will not break end mill )
G1 Z[#] F[#]
# = 1 (1 is right, 2 is left)
# = #
O while [ 1 ]
# = [# - #]
O if [# LT [# - #] ]
# = [# - #]
O endif
G1 Z[#] F[#]
(Depending on direction, we go to X1 on the right and turn total_angle,)
(or go to X0 on the left and go back to ZERO angle)
O if [# EQ 1 ]
# = 0
G1 X[#] A[#] F[#]
O else
# = 1
G1 X[#] A0 F[#]
O endif
O if [ # LE [# - #] ]
O break
O endif
O endwhile
O call [#]
G0 X[#]
G0 A0 (go to 0 degree)
O endsub
M2
Nice - to bad you can't use a hob ? I think that what thread cutters
are or Cob... They have cutters a foot long and 6" in diameter -
coated and all - here in Lufkin - the foundry at Lufkin Industries has
to do it all. Massive gears and massive bolts and nuts.
The traditional donkey that pumps out oil is twice as long as those made
by Lufkin. Their custom way saves space and when in buildings (hiding
the pump) it becomes important.
Martin
Yes, to do it properly, I would need to orient the rotary table at
angle to axis X. Too difficult for me to do it. I will mess with
making threads to see how geometry affects fit and how I can
compensate by fudging the diameter.
i
twice now, the auctioneer has called them taps. Makes for a really
good deal, I got one lot of 30 "taps" for $100. Even overheard one guy
saying that guy was crazy bidding $100 on taps.
Karl
For a 1MM pitch, a hand ground, single point hss threading tool probably
would have worked just as well and would also have produced the correct
root geometry.
Unlike iggy, I'm not good at selling things. I do plan to have the
best estate auction anybody has ever seen. I think, he who dies with
the most toys, wins.
karl
Thanks.
Converting a Bridgeport milling machine to Linux is also a skill.
And yapping on forums about "having access to a friend's shop" is not
a skill.
As for single point threading, my current problem is that the spindle
has to be on brake. However, spindle brake right now is tied to
estop. It only activates when the mill is e-stopped, and deactivates
when the mill is out of estop. Fixing that requires me to spend a
considerable time writing emc2 logic statements (to interlock brake
and estop and spindle running safely). I do not have time for this
right now.
i
And I do it with a kind word.
Exactly, and lately, scrap metal.
Yes, and there are plenty og great people to talk to.
This CNC conversion project, was not exactly a machine building
project. It was mostly about figuring things out, logic, wiring, etc.
i
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.