Myford ML7 motor and switch rewiring

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Myford ML7 motor and switch rewiring

This topic has 6 replies, 3 voices, and was last updated 5 October 2022 at 20:04 by Jon Halland.

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18 August 2022 at 20:29 #610288
Jon Halland
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@jonhalland84811
I'm going to rewire the Myford ML7 motor and Fwd/Rev switch. The motor is a Metropolitan Vickers with a 3/4'' BS Conduit gland (16 TPI thread that screw into the casing) and a flexible metal conduit is screwed into the gland. The conduit (16mm outer diameter) is knackered and too short, so either needs to be replaced or substituted with something else.

My preferred solution would be to replace the 4 single wires that currently go to the engine in the flexible metal conduit with a 4+ground cable, so I can ground the switch and motor casing. This would also be able to bend more sharply as the cable come straight out the back.

Is it possible to get a cable gland that tighten onto the cable instead of the flexible conduit screw in and has a 3/4'' BS Conduit thread?

Alternatively is it be possible to get a sharp bend that has 3/4'' BS Conduit and use flexible metal conduit?

Thanks.
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18 August 2022 at 20:29 #14643
Jon Halland
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@jonhalland84811
18 August 2022 at 20:37 #610290
DC31k
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@dc31k
Search for 'imperial conduit adaptor'. 3/4-16 male to M20 x 1.5 female. Female part can be shortened in the lathe as required.

https://www.edwardes.co.uk/products/lewden-pd1452a-3-4-male-x-20mm-female-conduit-adaptor-galv-steel

Clean up what you have, bore a lump of brass to suit and loctite it in. Drill and tap perpendicular to this M20 x 1.5. Then you have the right angle one you seek. The advantage of the loctite is that you can clock it correctly before it sets.
18 August 2022 at 21:02 #610295
Robert Atkinson 2
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@robertatkinson2
Another option would be to use a PG21 thread gland and tap the motor housing to suit. Thread is 28.3 major diameter, 1.59mm pitch. A commercial electrican might run a tap through it for you to save buying one.
Lots of galnd options with PG 21 thread

e.g. https://uk.farnell.com/w/c/cable-wire-cable-assemblies/cable-management/cable-glands-locknuts-fixing-tools/cable-glands?thread-size-imperial=pg21&cable-gland-material=brass|brass-nbr-nitrile-butadiene-rubber-nylon-6.6-polyamide-6.6-|metal

Ronert G8RPI
18 August 2022 at 21:16 #610300
DC31k
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@dc31k
Posted by Robert Atkinson 2 on 18/08/2022 21:02:18:

Thread is 28.3 major diameter, 1.59mm pitch.

The PG thread series is nearly as obsolete as BS Conduit. I only have a 28.3mm x 16 tpi tap (and no 17/16" tapping drill). Would that be OK? How many commercial electricians carry metric conduit taps let alone PG ones?
22 August 2022 at 16:41 #610737
Jon Halland
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@jonhalland84811
Thannks for your suggestions. I did not manage to get further with this during the weekend.

Another option could be to file the female thread in the motor housing down and use a PG11 gland with a nut on the inside. I just got some, one to be used on the switch power lead.
5 October 2022 at 20:04 #616131
Jon Halland
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@jonhalland84811
I ended up using the original now very shiny brass glands with some 16mm pvc coated flexible conduit.

New 5-core cable on the switch/engine, so switch and motor casing now has earth connection.

Power plug/switch with a PG11 (easy fit for the hole in switch casing and the cable).
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