Double Start Thread Orientation

[frankjconway]

Strange one here. I have some cylindrical castings that have bosses (radially) in them that will be tapped. There is a double start thread along the long axis of the part. My question is: Can I relate the thread start to the bosses? Stated another way, can you control the spindle angle to the thread start point. I would think there is a way to do it, because just having the capability to make a double start thread (which we have done) implies that the position of the carriage is known relative to the spindle angle. I know milling machines have a spindle orientation M code. I'm not as familiar with lathes.

Thanks,

Frank

 

[MikeHalloran]

You can control the angular orientation of the thread start relative to the cast bosses, if your tooling controls location of the bosses relative to the spindle key.

So, for example, you would stop the lathe spindle in a known position, and orient the casting in a known orientation while clamping it. On an ancient engine lathe, you would then engage the half-nuts and leave them engaged and cut the thread while the carriage and spindle remained locked together by gears. CNC lathes do it electronically, but they do it.

You would have to do something analogous if you machined the threads in a mill, which is another option.

By 'relate', you mean 'specify on a drawing', right? Sure, it's done all the time, for stuff like cannon breeches and bottle necks and electrical connector shells.



Mike Halloran
Pembroke Pines, FL, USA