If carrying out a Class 1 PAT on a machine tool it is important to totally electrically disconnect any electronic equipment on the machine to prevent damage to said equipment.
Denford are 1 of the manufacturers that post warnings do not PAT labels on their machines.

Emgee

I'd like to add to Robert's suggestions and recommend that the new user of anything machinery related should visually check the earth connection for robustness and security before going on to do a circuit check. Robert rightly makes the point that a whisker of wire contacting the frame of the machine will permit enough current to flow to satisfy a multimeter; one way around this is to be sure that a robust physical connection is present.

That probably means taking covers off etc; that in turn begs the question of invalidating the warranty. I'd hope that a responsible commercial vendor would be able to get himself past that hurdle and not get all hoity toity about it. The user needs to know of his own certainty that the earth is satisfactory.

HTH Simon

Edit – for clarity

Edited By Simon Williams 3 on 28/05/2020 12:11:40

I remember our Safety Officer getting very upset at contractors who applied a PAT test to fixed heaters.

They said they were correct but as he said if you need a tool of any kind to assemble the connection/supply then it is not portable! The only tool you can use to connect/disconnect is your hands!

You need to remember that machines are sent out with little or no inspection despite what the seller tells you.

You have only to read some of the posts on this Forum to see that.

Cars are not much better. It pays to check EVERYTHING before using any machine.

The suppliers goal is to Get it out—Get the money in ! Full stop !

You don't believe it ? Read a few posts on this Forum and you might see things in a different light.

Don't even ask how I know.

This is a interesting question , If your motor is not attached to you lathe IE Mounted as a seperate unit it is quite possible that the only connection to the lathe may be your drive belt, This willl not provide any earth connection very easy to over look? You can buy a Plug for 13amp socket which has its own built in protection together with a manual reset in the event of a power failure , If you are using 3 Phase then more important because off the extra voltage to get a Electrician to check and test with a Megger for a Insulation test of either 500 volt or 1000 volt , Your Life is worth more than this simple test .

Take Care and check your equipment is safe for all .

Once remeber asking someone where is your earth connection its that lead there in the bucket of earth.

Take care Bee M

I have two vintage AEG corded power tools. The packaging of the first, a two-speed hammer drill, bore the dual insulation box-within-box symbol, but the tool itself (no such symbol on plate) had a twin and earth lead. The second tool, a jig saw, did carry the symbol and the legend "DO NOT EARTH" and, of course, had a twin only lead. Both tools had exposed metal gearboxes.

I recall querying the drill anomaly with the seller and coming away with the impression that I had bought an item on the cusp of the move to dual insulation. This must have saved a lot of copper but I wonder whether one system is actually safer than the other?

Robert Atkinson 2:

Thank you. I get the impression that corded tools are fast disappearing in favour of cordless and I suppose the inconvenience of the 110V transformer has contributed to that.

I bought a lovely piece of equipment from a reputable american supplier, nicely finished, painted etc. but wouldn't power up and on inspection found that the lovely paint finish was also a lovely HR for the earth conn. Easy fix but just proves that a 4 figure priced piece of equipment was never powered up on completion, which they confirmed, they only test the component parts before assembly!!!!

When I wired up a VFD and three phase motor to the Tom Senior mill, I paid great attention to a proper earth connection. The VFD is earthed, the motor and the metal case plus its locking door are also. Of course this is in a museum, not a home shop, so the standards have to be up to PAT testing and checking by a qualified electrician.

I think most of your questions have been answered , If you have good continuity from your plug top to all points that you tried on your Lathe this all sounds fine, PAT is another question as I do not consider a lathe is portable because you do not keep moving same around . A seperate earth will probably need to be a stake of 3ft or 5ft and need 6mm cable together with a earth leakage trip to work correctly this i do not think you need . The supply to your workshop is possibly a question I do not know what you have. Most portable appliances are now battery powered and double insulated.

Good Luck.

Bee.M