On 24 Aug, 00:35, jontom_...@hotmail.com wrote:
> On 23 Aug, 23:51, Mark Rand  wrote:
>
>
>
> > I would suggest that:-
>
> > 1) It's a nasty compromise that reduces the size needed for the apron and the
> > cost of the lathe :-(
>
> Not sure I totally agree with your suggestion here Mark, it wasn't
> "nasty" enough to stop Schaublin using "the robust, buttress-thread,
> 4mm pitch leadscrew, for both screwcutting and the sliding feed", and
> I don't think many describe them as compromised down to a price - at
> least not a price I could afford :-)) To be fair though they didn't
> bother with power cross feed at all and the drive system for the
> leadscrew was far from simple, so as you say you pay your money and
> choose your compromise.
>
>
>
> > 2) It results in self cleaning half nuts and keyway :-)
>
> > Take your choice.
>
> > Mark Rand
> > RTFM- Hide quoted text -
>
> > - Show quoted text -
>
> Helps with the sale of replacement half nuts as well, at least it does
> if the lathe is good enough in other ways to last a reasonable amount
> of time.
>
> Regards
>
> Keith

Sorry to reply to my own post but on reflection after another glass of
white, I need to clarify my comments which were merely intended as a
"humerous reposte" to Mark's comment.

I don't want anyone thinking that Schaublin actually used anything as
vulgar as a "slotted leadscrew"; although the leadscrew does in fact
do both tasks it is "an exceptionally large (40 mm diameter and 4 mm
pitch), hardened and ground, running in angular-contact bearings and
clasped by long nuts provided with positive oiling" (see Tony's Lathes
page). On the later 125/135 and later machines they do also provide
power cross feed but use a shaft that runs down the back of the
machine driven by bevel gears. They still do though use the leadscrew
to provide both threadding and sliding feed, so that part of my hunour
is correct.

Regards

Keith.