View Full Version : CNC threading question

05-19-2009, 07:50 PM
I have an easy question for you guys. When threading on a manual lathe the compound is often set to 29 1/2 or 30 degress and is used to advance the cutter. I understand this is to have one edge of the tool doing the majority of the cutting.
How do CNC machines feed the cutter? Do they plunge straight in at 90 degrees or is there something in the programming that offsets the cutter on each pass?

John Stevenson
05-20-2009, 03:58 AM
They feed in in various ways just like manual machine choices.
How they do it can differ.
It can be dealt with at design level in CAM, usually by selecting the infeed angle from a dialogue box, or it can be handled by a parameter in the G code that tells it the angular move.

Usually though most lathe threading is done from a canned cycle on the machine where you call up a pictorial of a generic thread and fill the boxes in as regards length and pitch. Some will have this angle handy on screen but others will have it on a settings page.

The moves are then controlled by software.

More advanced systems have choices. You can take off all on one side, you can take off all on one side except for the last spring passes where it infeeds so it cleans the trailing flank and some have the ability to take off alternate sides per pass.



05-20-2009, 10:00 AM
Thank you for the detailed answer John.