Re: Sherline Spindle Pulse disk for threading

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Steve Blackmore <steve@...> wrote:

>
> On Sat, 10 Nov 2007 15:59:37 -0800, you wrote:
>
>
> >You don't want it adjusting over the threading pass or even a different
> >speed per pass. You want a stable spindle speed in the first place.
>
> Agreed, the latter is the less of two evils.
>
> >I do have a question for you Steve. If you are using the G76 to

cut the

> >threads, one of the parameters is thread depth. If, after the G76 is
> >done, the nut doesn't fit because the lathe and work flexed such that
> >the depth wasn't cut, how do you fix this? Set a deeper depth and run
> >the G76 again? Do some sort of special G76 as a single spring pass?
>
> Not here - I'd scrap that part and re-do it with more passes.
>
> I always run one or two spring passes anyway.
>
> You need to set the parameters so that doesn't happen in the first
> place. If that means doing test pieces on the same material, so be it.
>
> BUT - If the lathe flexes that badly, get a new lathe ;)
>
> For fine work that's likely to deflect I always use a die and holder or
> box tool. Support with centre & tailstock on long threads.
>
> Steve Blackmore
> --
>

Hi, I insert a tool change command to stop the program and check the
thread. After the tool change I have another G76 with the full depth
of thread as the first cut parameter in the threading wizard. I can
then go over the thread as many times as I want with the finishing
cuts only.
If you don't have a very steady "true spindle speed" reading in Mach 3
it is impossible to cut a thread using G76. The thread cut will be at
a different pitch with every pass. On a long thread it will just
effectively turn the shaft down. I discovered this after about a year
of trying to trace the problem, blaming noise, cables, servo drives,
computer viruses,etc.
Regards,
Glen.