Re: [CAD_CAM_EDM_DRO] Re: Electronic Lead Screw Drive Article ? | Threading Ratios ?

Hi Vaso,

That's certainly a way to look at it. Just back up the Z axis far enough to get
the backlash out, then start another pass.

TurboCNC is doing CNC threading on the little Sherline lathes, and they don't
have half-nuts! The Sherline threading kit DOES have an engage mechanism for
the "back gears", but I don't believe that's used for CNC.

What about the FROG? probably does the same "electronic" gear ratio, and also
allows threading on Sherline and Taig lathes. Ought to be able to apply the
same logic to a full sized lathe as well.

What was that article again? I think I'll go re-read it.

Alan KM6VV


Vaso wrote:

> This PLL circuit fixes the speed of the lead screw to some ratio of
> the the spindle speed. The circuit as it stands has a fixed "table"
> of ratios, but it seems to me - with microprocessor control - any
> ratio between spindle and leadscrew speeds is possible, so this
> circuit could cut any metric or English threads - even non-standard
> threads.
>
> The problem of releasing the half nuts and traversing back manually to
> pick up the thread would still remain, but the half-nuts need not be
> released - the traverse direction can simply be reversed...
>
> Am I missing something ?
>
>
>
>
>
>>>I have an old SB lathe with manual change gears.
>>>
>>>I was thinking something like this would be a way to just add variable
>>>speed to the spindle and also add electronic thread cutting.
>>>
>>
>>I don;t think this device, as it stands, would be useful for Imperial
>>threading.
>>It was aimed at standard metric threads, where a very limited number
>>of ratios will suffice. It could probably be expanded on to give most
>>of the standard imperial threads. But, 11, 13 and 27 would be a
>>problem, for sure. I'm not sure it actually has a limitation to
>>even ratios, but I thought it might.
>>
>>Also, I'm not sure what happens if you stop the spindle, or open the
>>halfnuts and have to move the carriage. I guess that would be the same
>>problem as with standard threading gear systems, you have to sync the
>>carriage to the leadscrew with the threading dial, and the thread pitch
>>determines which marks you can use.
>>
>>Jon
>