You have answered your own question correctly. A Double pole Double throw toggle switch with a centre off will do what you require. All you have to do is to wire a crossover at the switch (feed the Z1,Z2 to the two centre contacts and wire cross over links between the two pairs of outer contacts and then wire the start winding  to one end of the switch. I assume that the switch shown in your diagram is a centrifugal one to cut out the start winding once the motor has spun up, if so then you don't need to worry about the switch being changed over when the motor is running as the start circuit is already switched out at this point. The motor will only start in the opposite direction once the motor has stopped and has been re started.

Suitable switches can be found on Ebay

A NVR on the incoming supply is a good idea as it protects against an inadvertent restart if the power supply is interrupted.

Martin

Edited By Martin Cargill on 14/06/2020 20:50:06

I wired my Quorn with a DPDT toggle for forward/reverse, and a cheap NVR switch from ebay for stop start.
Because I move the grinder around, I also used a kettle socket and detachable lead, to save tripping myself up when I get old and doddery.
It also means it's likely to unplug the lead if I accidentally catch it on something, rather than dragging the grinder off the bench.
This makes it a particularly good idea to use an NVR switch to save accidental re-starts.
It also helps avoid trying to reverse the motor by accident when it is still spinning down, which is the danger with a centre off toggle.

Bill

Welcome to The Club.

The Stent Owners Club.

Bought mine as a S/H unfinished project too. Funny old world. Innit.

Yeah, i built my Stent using a S/H washing machine motor with a new external capacitor, as i knew washing machine motors have to run both directions.

Double toggle switch is from a Brit motorcycle, so originally 12V.

Never been any elektrickery problems.

Got over 200 hours of build time in it, and at least half that in use.

Happy playing.

Yes, i did'nt like the look of the motor plate design in the Stent drawings and others on the web, so changed how my motor was bolted on, adjusted, and the Z column.

This thread of interest to me as I have acquired one part-made. Some interesting ideas above, including rather better guards than as-designed.

One modification I think published in MEW some years ago, is to reverse the layout so the motor is to the left of the column. That improvement puts the normal position of the spindle near the centre of the table.

I am pondering a system slightly based on the BCA Jig-borer's drive to place the motor on the base, removing its weight from the column. Also to modify the main spindle bearing-block, replacing the stepped bore with a single diameter and a spacer, to facilitate any future bearing replacement.

–

Colin –

Useful mods to the Graduating Tool. When I engraved the hand-wheels on my Hemingway 'Worden' T&C Grinder, I ground an old cutter or broken centre-drill to shape and simply held it in a collet in the mill spindle, in conjunction with a 'Warco' badged clone Vertex dividing-head. A lever-type tool such as the Hemingway one you show would be the better choice, and a suitably beefed-up version could also be used as a key-way cutter.

'

Geraint –

Your Q3. I do not have the original construction serial but the Blackgates drawings show only cylindrical cutter-holders. However it should not be too difficult to make some form of holder that can be swapped with the block that takes the cutter-holders.

Or indeed has a cylindrical body but rectangular inner to match the existing part. The 'Worden' T&C grinder uses something like this for lathe tools with a slotted rectangular block to hold the tool, mounted across a cylindrical spigot that fits the collet-block.

My guess is that when the Stent was designed, most model-engineers typically used an off-hand grinder for lathe tools, working to gauges when necessary. Perhaps the introduction of insert tooling has made us more aware of accurate turning-tool geometry, especially for applications like screw-cutting.

Edited By Nigel Graham 2 on 21/05/2021 21:07:32

Thanks all

Nigel – I've requested drawings from Blackgates. Hopefully they'll come through early next week…..and will give me a few ideas

Bernard – this is what I love about this forum…even as a total newbie to model engineering and forums in general. The ability of folk to just explain something that wasn't in any way obvious to me in one sentence…….and suddenly the penny drops and I'm there thinking – of course, why didn't I think of that!!

G