Another threading question

[desmotom]

I am turning a 2.75 ID 6 tpi single start acme and the finish is not quite the best. A little chatter on the sides of the thread. Tried running at 650 rpm and 500 not difference. any suggestions?

 

 

(6 TPI ACME THREAD)

(USE THREADING BORING BAR)

(TOOL PROTRUSION)

G50X-10.Z10.

G97G40M42

G00S500T0404M03

X-2.7Z.1576M08

Z.1037

M24

G76X-2.9075Z-2.275I0.K.065D300F.1667A29

G00Z.1M09

X-10.Z10.

T0400

M05

M01

[Kevangel]

Did you try going to "an extreme" like 100 rpm and see if chatter stops?(then work rpm up). Know on grooving on bigger diameters (on my equipment)higher RPM always tend to chatter.

[crazy^millman]

Have you tried grinding a postive lead on the cutting edge??

[JDowe]

On the thread cut tab

Under the NC code format

There is a selection for alternating

which writes long hand code and alternates

cutting on the right side and then the left

side of the tool - maybe this would help

[desmotom]

I slowed down the rpm to 250 and looks pretty good now. I think in the future I will used the long hand method and and copy and paste the last passes for spring cuts.

[FP1]

I have always had better results using G92 threading cycle over G76 when it comes to acme threads. This way I can control the depth of each pass accurately to the insert manufactures depth per pass charts. Always had good luck with Tool-Flo brand acme inserts.