Where can I get a 3/4″ strain relief bush?

[Andrew TinsleyParticipant @andrewtinsley63637]

Just been overhauling an old English Electric sleeve bearing electric motor. It is missing its 3/4" strain relief fitting for the incoming supply.

I cannot find one anywhere. Maybe I am using the incorrect search description? I know that most fittings are now metric, so are the old 3/4" bushes an extinct species! If so, has anyone got one that I could buy, or know of a source?

Thanks,

Andrew.

[Andrew TinsleyParticipant @andrewtinsley63637]

[colin branniganParticipant @colinbrannigan54160]

I would think 20mm is the new 3/4, may need to open the hole a tad, along with 16, 25 etc etc.

Colin

[Andrew TinsleyParticipant @andrewtinsley63637]

Looks as if I have been using the wrong descriptions. Using 3/4" cable gland gave me plenty of hits! Apologies for using up valuable forum space.

Andrew.

[DC31kParticipant @dc31k]

Posted by Andrew Tinsley on 14/06/2020 17:48:29:

Using 3/4" cable gland gave me plenty of hits! Apologies for using up valuable forum space.

Your excitement may be premature. I just did the same search as I often need these and every 3/4" gland that comes up is 3/4-14 NPT.

3/4" BS conduit is 16tpi (see http://www.oldengine.org/members/diesel/Tables/conduit1.htm).

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

When I have bought them, they are always too long at both ends but that's nothing a hacksaw cannot correct.

Edited By DC31k on 14/06/2020 18:41:10

[Andrew TinsleyParticipant @andrewtinsley63637]

Hello DC31k,

There is an Ebay seller doing 5 plastic 3/4" BSP cable glands for just under £5 including postage. These will do for my application.

Thanks,

Andrew.

[EmgeeParticipant @emgee]

Posted by Andrew Tinsley on 14/06/2020 21:28:12:

Hello DC31k,

There is an Ebay seller doing 5 plastic 3/4" BSP cable glands for just under £5 including postage. These will do for my application.

Thanks,

Andrew.

They will be 25.9mm diameter threads, much bigger than the 3/4" you wanted.

Emgee

[duncan webster 1Participant @duncanwebster1]

'I've just measured a gland I've had for about 40 years, it is just over 3/4 diameter but is 1.5mm pitch, so probably actually metric. However when I try it in a nut off a modern metric gland it is pretty sloppy, so I wouldn't be at all surprised if it would go in your motor. Downside is that it is probably designed for flat cable. If it might be of some use let me know and I'll post a picture

[DC31kParticipant @dc31k]

Posted by Andrew Tinsley on 14/06/2020 21:28:12:

There is an Ebay seller doing 5 plastic 3/4" BSP cable glands…

As Emgee says and the eBay picture shows, these are G3/4" thread, or 3/4 BSP. The 'size' number in a BSP thread is the nominal bore (ID) of the pipe so the glands will be both too big and the wrong pitch.

Non-American imperial conduit will have a BS31 imperial conduit thread on it.

Duncan's pitch measurement is explained by the proximity of 1.5mm and 1/16" on the number line. A 16tpi gauge will also fit. Measured over a low number of non-precision threads, it is difficult to determine which one is correct.

[StueeeeParticipant @stueeee]

I've just run a 20mm x 1.5 tap when I've come across this issue, never needed to re-drill.

Although there's a slight divergence between the 1.5mm "new" pitch and the 16 TPI original, it's never been noticeable in the short length of thread where a gland etc. would screw into.

[Andrew TinsleyParticipant @andrewtinsley63637]

Oh my word, fancy making the old mistake of thinking that BSP threads are the same diameter as the nominal size! I hang my head in shame. To make things worse, yesterday I explained to my son in law that 1/2" BSP backing nuts for domestic taps had a much larger internal diameter than 1/2". I then go and make the same mistake!

Maybe a PG11 cable gland and locking nut would do. I may have to put a drill down the existing tapped aperture to give clearance.

Better still I could perhaps take up Duncan's offer and cross his palm with silver?

Andrew.

[duncan webster 1Participant @duncanwebster1]

If it's any use send me your dirt my address by pm. It's of no value to me, so I don't want anything for it. Just one of those things which is too good to throw away

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