Electric reverse switch for bench lathe

[Zetomagneto]

This looks to have a screw on chuck, strong possibility of it unscrewing and falling off when reversed!

[Biddlecombe]

Yes it is screw on. Thanks to you and others on this great forum I have resisted the thought of fitting the reverse switch. However I would mention that lots of Myfords are fitted with similar switches and they have screw on chucks.
Thanks very much. I hope you liked the story anyway.

[bob46320]

Good luck with getting that swith to do what you want it to do. You really need a proper lathe motor reversing switch.

[Biddlecombe]

I thought that was what I bought. Never mind.

[Parazine]

Single phase induction motors usually employ two windings, one is connected across the incoming supply, the other is similarly connected via a capacitor (likely the round object on the side of the motor in the photo). The capacitor may be permanently connected or it may be switched out by a centrifugal switch when the motor has reached some speed. The latter type develops more torque and is suitable for starting machinery. The first type is better suited to light loads, e.g. fans. Yours is probably (but not necessarily), a switched motor.
In order to reverse the motor, one of the windings, usually the capacitor fed one (the "Start" winding), has to be reverse connected, so that the current flows through it in the opposite sense. The switch you have would be suitable to do this but the connections to the start winding must be positively identified and isolated from the connection block so that it can be remotely switched in forward and reverse modes.

Unfortunately, in the absence of any manufacturers wiring diagrams, it will be necessary to work out the connections from first principles, which will need someone with fairly deep electrical engineering skills, armed with a DMM. The link below will give some ideas but obviously relates to some modern motors in terms of the actual connections.

http://www.sentridge.com/wp-content/uplo...ng_1ph.pdf

Unless you can find someone who can work it out for you (unfortunately you're too far away for me to help), I would leave well alone. As people have commented, there aren't many times you need to reverse the lathe and most of those you can work around.

Good luck, it looks like a nice machine!

[Bob Culver]

Flat belts can now be a problem. I have seen car timing and other belts used, some upside down.
If you have not had one before a problem is that the lathe can become the primary hobby. Esp one with T slots.Being more safe is one consolation !!

If you draw the switch 3 times with the 3 states of non connection and connection (crosses) how to utilise becomes more apparent. The mains pair in/out needs be switched on/off and the start pair in/out reversed.
Assumingthe motor has a centrifugal switch it is vital the start winding is not soehow wired to omit this.

[Colin Wilks]

I had to renovate the Dewhurst reversing switch on my Myford lathe recently. What I learnt in the process was:
1. Screw on chucks can come loose if run in reverse.
2. The lathe needs to have an on/off switch separate from the forward/reverse switch.
3.If your lathe motor has a centrifugal start winding you will hear the switch make and break as the motor speeds up and slows down.

4. Never switch the earth supply, which as Bob said, needs to be continuous.
5. Ensure the body of the lathe and the body of the motor are both earthed (motors tend to be rubber mounted to prevent vibration).
6.For safety the on/off switch should be a NVR type (no volt release) so that if the mains is cut whilst the lathe is running it will not start up unannounced when the mains comes back on.
7. An emergency stop button is a good idea.

In the end I have left the Dewhurst switch off so my lathe only runs forwards, but I have taken the mains and motor wiring into a separate junction box so that it is easy to reverse the start wiring manually should I need to reverse the lathe at some point, or if I decide to fit a reversing switch in the future.

[Bob Culver]

My own lathe uses two cheap household switches (one of two way) and I soon learned to exercise caution with the sequence!
The DFK switch has terminals to both break the line wires and reverse the start winding and mid  position with all disconnected.

The handwheel on end of leadscrew  was the only hand end feed on some basic lathes. Is the main feed inconveniently rapid?

[Biddlecombe]

The only thought I had was for an easy way to get an occasional reverse. However I have never owned such a small lathe having been inducted at the age of 8, 64 years ago by my father with overhead drive systems and belt drives and having my own engineering business for a few years with Colchester and Harrison lathes. I was never involved in the electrics. I am now happy to abandon all thoughts of electric reverse. Bob, I am happy with the drive speed and can deal with the change wheels. Thanks all for your help.  Whilst here I am interested in purchasing  a 4 jaw chuck. The 3 jaw is 3 1/4 inch diam. With 1 inch x 12 tpi thread. So something similar.
Peter

[Tony Griffiths]

  Whilst here I am interested in purchasing  a 4 jaw chuck. The 3 jaw is 3 1/4 inch diam. With 1 inch x 12 tpi thread. So something similar.
Peter

Apologies for missing your post. I've been lost in the mountains for a few days. A new, unused Grayson! What a fantastic find; it will serve you well.
See: http://www.lathes.co.uk/grayson
For advice on chucks and backplates: http://www.lathes.co.uk/latheparts/page7.html
You've probably sorted out the electrics, but if not, this might help: http://www.lathes.co.uk/page27.html/
If stuck on any point with the lathe just give me a call on 01298-871633; I'll be pleased to help.
There never was a manual for the Grayson (or many other small British lathes), but in 1946 the definitive book for amateurs was written that gets grips with lathes of all types and ages, including yours. The text is now in a rather old fashioned syntax - but none the worse for that,
"The Amateur's Lathe". It assumes no prior knowledge and goes through all the basic and some advanced machining processes in a clear and logical way. Included are details of how screwcutting and power feeds works and how to set changewheels to provide a slow-speed carraige drive and generate pitches. Charts for various pitches of leadscrew as commonly used on small lathes - one suitable for your lathe will certainly be amongst them.
Various simple projects are also included with engineering drawings that allow some useful accessories to be made. How to sharpen tools, set tool angles, read micrometers and verniers, etc.
https://store.lathes.co.uk/books/amateurs-lathe