My lathe lacks such a facility. Having run against a stop, under power, and damaged the rack and ruined the pinion and shaft, I do want to spend another week curing the self inflicted problem.

My technique is now to disengage the power feed a few thou from the stop and to feed, gently, the last few thou upto the stop.

The turning is done to length, and the machine remains unstressed and undamaged, so everyone ends up happy.

Howard

Hi if possible I would like the info on feed stop adjustment. I’ve got an apron from a Bantam in pieces at the moment and would like to adjust the feed “knock off” pressure before I reassemble.

Ashley

I'm intrigued, how is the interlock bar removed?

The knock-off on my Bantam appears to have the original factory setting, since I doubt that the original technical college owners adjusted it. It works OK, apparently without excessive force, though there is a fair clunk on disengagement. I do use it most of the time. However, it is possible to set a sufficient depth of cut to cause spurious operation, but I just accept that as a compromise in a useful but somewhat mediocre design.

Edited By Macolm on 25/01/2023 20:47:59

Since you are able to apply that description to it, you must have in mind some superior methods of achieving the same thing.

Please do feel free to share these methods and the machines on which they appear.

One might say that there is a 'fair clunk' when you pull the trigger of a firearm to discharge the weapon. In that contect, it is hardly a fault.

Realistically the thing is best considered an overload safety device to disengage the drive before serious damage occurs. As such it's a little kinder than the common shear pin. One of which is also fitted.

Although it can be adjusted so the release force is reasonable such adjustment limits the cut that can be taken before the loads become great enough to trigger the release. Sufficiently so that hefty roughing cuts become impractical.

There is an inherent mechanical delay between the carriage stopping and the mechanism running to the end of its travel to release the drive. This delay doesn't affect accuracy because the saddle has to be hard stopped before the release mechanism starts to drive. However it does mean that things are engaged under full drive pressure as the mechanism moves them out of engagement. Less than mechanically kind tho'.

The single tooth dog clutch arrangement used by Holbrook, Pratt & Whitney et al is operated by a spring loaded trigger so it only has to disengage against normal drive loads rather than maximum stall force. The spring gives an inherently fast release too. However the trigger permits some positional scatter as its release point cannot be absolutely defined. Never enough to be an issue on machines of such quality when in good order but in old age, especially if the machine has been neglected, the trigger point can become undesirably variable. One day I shall dig into my P&W to fix things but needing to lift the headstock is a little daunting.

Clive

Edited By Clive Foster on 26/01/2023 14:19:09