screw cutting

[geoff adamsParticipant @geoffadams14047]

[geoff adamsParticipant @geoffadams14047]

so i want to screw cut threads on cnc lathe g code no problem. carbide tip tool holders do you need a different holder for every thread ie metric coarse metric fine. one tool holder and different tips or two tool holders ? also need to cut 1/2 32 tpi thread do i need a another tool holder very confused any help please many thanks ( shank size 12mm)

Geoff

[JasonBModerator @jasonb]

Depends how fussy you are. Inserts come in two main types – full form and partial form. Full will have the correct radius to form the crests and valleys so you need one for each pitch. Partial will cut a deeper more angular valley and the crests may need a quick dressing with a file but one insert will cover a range of pitches.

One holder will take various inserts – full partial. metric UN, etc

If your 1/2 x 32 is an ME thread then you will need 55deg inserts, if UNC then you could get away with partial metric or a specific full form 12tpi UNC insert

[old martParticipant @oldmart]

With a tool shank of 12mm, you are limited to 11 ER & NR, and 16 ER & NR laydown inserts. The thread pitches overlap the two sizes of toolholder available to you in both internal and external types. A good source of inserts which are available singly is APT which are very good and not too expensive.

[geoff adamsParticipant @geoffadams14047]

thanks guys

rotagrip sorted me out with tool holder and tips be here in two three days will do everything i need

many thanks Geoff

[Neil LickfoldParticipant @neillickfold44316]

Some holders come with different shims for different helix angle ranges for the thread being cut. Also there is a shim for left hand threads as well. Often companies will have in their catalog the helix angle range of that shim number for their holders. Well worth while to read about it.

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