Does not look like a retracting top slide to me.

The advert describes it as a geared and retracting top slide.

Colin

The pictures show a very non standard L shaped lever on the side of the top-slide base.

If it is a retracting top-slide as described the top-slide nut could be mounted on some sort of rack slide operated by a gear on the lever shaft to give the retracting action.

Objectively an considerable amount of work for a monumentally stupid way of going about things. Especially as that lever is on the chuck side of the top-slide when it is set at 90° to the work. Which is the position where a retracting top-slide is most desirable. Reducing the precision and stability of the top-slide nut mount to implement an improvement of effectively only theoretical value seems somewhat unwise.

Unless someone knows of hidden crafty engineering to sidestep such problems.

Historically effective slide retraction systems have been based shifting the thrust bearing and dial assembly back by either on a concentric quick thread sleeve or a cam / eccentric system on a vertical or horizontal shaft. For example my P&W B has the concentric quick thread sleeve on the cross-slide screw. The Geo. H Thomas geared and retracting top-slide system uses the vertical shaft which appears overly complicated in some respects due to the dependance on accurante non-concentric working when making the parts.

Clive

What did it cost new ?

I haven't seen this retracting slide design before. I think Clive Foster's negative comments are hasty and harsh. Why should a well-engineered moving nut be worse than a moving feed-screw thrust bearing? If the user screw-cut with the top-slide slewed round, the handle is more accessible than it would be on t'other side, especially if tailstock support is employed, when the tailstock would likely get in the way.

Same with me.

I was curious about the top slide gadget, but I wondered what it is for. A bargain if you ask me. I was surprised that the VSD was still working.

Think about normal operation of the machine: the only parts your fingers touch are the three dials on compound slide, cross slide and saddle.

To retract the lever shown (it has to point 'forwards' to engage the tool in the work), you have to put your digits closer to the spinning parts than might be desirable. So while the principle might be good, the ergonomics of what is shown are less so.

It has struck me while typing this that perhaps something could be installed over the grease nipple shown on the end and act as a remote release (like the cable you can buy for a camera). That would increase the safety.

It is the detailed design of its operating mechanism that needs consideration more than the concept of a moving nut.