Using the Mill as a Lathe; Single Point Threading

[Geof]

I had done some posts on the possibility of single point threading in the other thread on using a mill and lathe and decided to test the idea.

First and second pictures show a single point lathe threading tool simply held in the vise being used to turn a piece of 3/4" brass slightly undersize with an undercut at the end.

Third picture shows the finished thread.

Fourth picture shows a nut screwed on; thread is 3/4"-10.

I got the size a bit small but it is not a bad effort for 20 or 30 minutes of playing around.

Obviously my concerns about chipping the insert were unfounded.

Here is the code:

%
O00000 (THREADING)
N1 G00 G20 G40 G49 G80 G90 G98
N2 G53 G00 Z0.
N3 (-----)
N4 T1 M06
N5 G43 H01
N6 S1000 M03
N7 G54 G00 X0. Y0. Z1.
N8 Z0.1 M08
N9 G84 Z-1.2 F100. R0.1 L1
N10 X0.005
N11 X0.01
N12 X0.015
N13 X0.02
N14 X0.025
N15 X0.03
N16 X0.035
N17 X0.04
N18 X0.045
N19 X0.05
N20 X0.055
N21 X0.06
N22 X0.065
N23 X0.07
N24 G00 Z1. M09
N25 (-----)
N26 G53 G00 X-8. Y-4. Z0.
N27 M30
%

[Shotout]

Thanks for posting this. I've been wanting to do it but I don't think the owner would approve of experimenting like this with his equipment so I haven't tried it. I like the fact that the repeat rigid tap function allows for multiple DOC.

[PBMW]

Thread milling...
I've used threading tools for a lathe and single point thread mills for years. Just a helix isn't it? Or am I missing something here?

[Andre' B]

I wonder if you can do the 29.5° cut on one side if you also increment the R value?

[Andre' B]

Originally Posted by PBMW Thread milling... I've used threading tools for a lathe and single point thread mills for years. Just a helix isn't it? Or am I missing something here?

He is using the tapping canned cycle with the PART in the spindle and the threading bar in the vice.
The question was if the threading insert would stand up to the reverse back out part of the tapping cycle.

[Geof]

Originally Posted by PBMW Thread milling... I've used threading tools for a lathe and single point thread mills for years. Just a helix isn't it? Or am I missing something here?

Andre' B is correct in his reply; here the tool is stationary in the vise and the workpiece is rotating in the spindle, identical to a lathe. Well I guess the tool is not stationary, it moves on the X axis, while the workpiece moves on the Z; more analogous to a Swiss Screw Machine I think.

Andre'; you can do the multitudinous calculations for the angular entry if you like. I can think of no reason why it would not work. and if you alternated up and down you could greatly reduce the cutting load, and the possibility of chipping. I did try cutting a piece of leaded but the tool moved in the vise; I think I did not have it adjusted on center well enough.

[Andre' B]

Give this a try if you want.
I changed the Z starting level to 0.2 so it does not jump up to the R plane.

I have to get some work done now.

%
O00000 (THREADING) 
N1 G00 G20 G40 G49 G80 G90 G98 
N2 G53 G00 Z0. 
N3 (-----) 
N4 T1 M06 
N5 G43 H01 
N6 S1000 M03 
N7 G54 G00 X0. Y0. Z1. 
N8 Z0.2 M08 
()
#33=0.005(DOC START)
#32=0.07(DOC FINISH)
#31=0.004(DOC INCREMENT)
#30=29.5(ANGLE)
()
(EVEN UP THE DOC)
#31=[#32-#33]/FUP[[#32-#33]/#31]
G84 Z-1.2 F100. R0.1 L0 
WHILE [#33 LT #32] DO1
X[#33]R[0.1+[#33*TAN[#30]]]
#33=#33+#31
END1
X[#32]R[0.1+[#32*TAN[#30]]]
G80
()
G00 Z1. M09 
(-----) 
G53 G00 X0 Y2. Z2. 
N27 M30 
%

[Geof]

Originally Posted by Andre' B Give this a try if you want. I changed the Z starting level to 0.2 so it does not jump up to the R plane. I have to get some work done now.......

Now you are getting fancy . I doubt whether I will ever use this technique, I was just interested to see if it would work.

[Vern Smith]

I really appreciate you guys taking the time to figure this out, there is a very good chance that I will use it rather than buying a $40,000 CNC lathe. My stuff is usually small and limited in quantity.

Vern

[Geof]

Originally Posted by Vern Smith I really appreciate you guys taking the time to figure this out,.....

Truth be told, it is fun doing this and it relaxes the brain from motre pressing worries such as how to make things faster, better and quicker.

In my example I made the position of the tool when it was turning the OD of the brass my X and Y work zero coordinates and the tool offset was with the end of the work at the tip of the tool. I was really on the wrong side with the tool which I why my X moves were positive which is not intuitive.

[PBMW]

Ahhh. I was missing something.
Cool stuff.