Screwcutting L/H Threads.

[Roger Williams 2Participant @rogerwilliams2]

[Roger Williams 2Participant @rogerwilliams2]

Hello all, I need to screwcut a l/h thread but am a bit confused about correct tooling. Im set up for normal r/h threading with inserts in a presumably r/h tool with a 1degree positive shim under the insert. The question therefor is, can I cut a l/h thread with what Ive got by changing to a negative shim, or do I have to obtain specific tooling to suit ?.. JBL dont sell anything for l/h threading it seems, unless Im looking in the wrong place.!. Many thanks.

[KWILParticipant @kwil]

Toolholders usually have a built in helix angle to which you add or subtract by means of the added shim. Without knowing what you are using, a bit difficult to add more. Talk to Peter at Greenwood Tools who can advise you and supply whatever you need.

[Roger Williams 2Participant @rogerwilliams2]

Kwil, thanks for the reply. Ive just waded through the Sandvik Coromant threading PDF, and it says in there that you can use a R/H insert to cut a L/H thread as long as the shim is changed to a negative one. Conversly, you can cut a R/H thread with L/H insert, provided you use a positive shim !.

Certainly saves buying both types of insert, just 2 different shims.According to the blurb, using the "wrong" insert may cause insert movement at the beginning of the thread, so care is needed. Thats what it says anyway. Cheers.

[KWILParticipant @kwil]

Peter is ex-Sandvik

[Roger Williams 2Participant @rogerwilliams2]

Hello Kwil, yes I emailed him and he sells -1 negative shims, but at nearly £15, I will shop around first ! Cheers.

[Nigel McBurney 1Participant @nigelmcburney1]

Why not just grind up a hss toolbit and make your own screwcutting tool,its a lot quicker and cheaper than shims and inserts.

[Roger Williams 2Participant @rogerwilliams2]

Hello Nigel, yes you are right, thats what I used to do, but after trying insert tooling, it seems to me anyway, so much easier this way , especially as Im not particularly brilliant at sharpening HSS tool bits !. A lot more expensive of course, but hey ho !. Incidently, you can get set up with an insert threading toolholder and insert from JB Cutting tools for just over £20. Cheers.

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