Lampholder: earthed metal or non-earthed plastic - which is safer ?

[Wilska]

Hello.
I have an old metal standard lamp from a charity shop . I would like to order gold coloured cable for it, so I must decide wether to get cable with no earth and fit a plastic lampholder , or cable with an earth and fit a metal lampholder. I have both types of lampholder and both thread onto the standard thread of the lamp perfectly.
I am only interested in safety in this case rather than the look. As a layman I can imagine safety advantages to both types . For example, if the cable failed at the base where it turns out of the metal stand, it would be best to have an earthed lamp. But if the cable failed at the lampholder, it would be better to have a plastic lampholder.
I have inspected the lamp and cannot see any reasonable cause of the cable insulation failing such as sharp edges or kink points.
Any thoughts appreciated,
thank you
W.

 

[EFLImpudence]

if the cable failed at the base where it turns out of the metal stand, it would be best to have an earthed lamp. But if the cable failed at the lampholder, it would be better to have a plastic lampholder.

If the cable is likely to fail at the metal base then it should be earthed.

Edit - By 'it' I mean the base.

 

[flameport]

If the body of the thing is metal, fit a metal lampholder.
Otherwise you have to either find some method of connecting an earth to the metal parts, or install the flex in such a way that the entire thing can be classed as double insulated.

 

[333rocky333]

As flameport says, providing there is continuity from the thread to the other metal parts of the lamp. then by connecting to the earth terminal in the METAL lampholder you hence earth the whole lamp.
Another option is use a plastic lampholder, that has a built in metal thread with integral earth terminal.
Usually the type of shade would dictate the type of lampholder is best

 

[Wilska]

I see. Thankyou for your replys. I think it sounds safest to earth the whole thing from a metal lampholder or use the plastic /metal threaded and earthed type rocky mentions.
Is this something you'd recommend an average layman can do, if they can wire a plug, its nearly as simple as wiring a plug. Ive also done a spur with 3 double sockets. I get the impression from for example B&Q guides that this is something the average householder would be expected to carry out themselves, or if they were elderly or unconfident perhaps a neigbour who does DIY, but not something you would pay someone to do ?

 

[winston1]

Ive also done a spur with 3 double sockets.

Have you indeed? If this is a spur off a ring you should only have one double socket on it.

 

[Wilska]

Ah, the whole house, built 1965 , is spurs, no ring. The work was subsequently checked by the qualified electricians who came to put a new spur in for the kitchen when it became apparent that the work was beyond me as there was the type of fuse box under the stairs that used fuse wire and they put in the sort that trips out with trips for each main spur. The socket spurs had been redone in the 90s and were ok but sadly the lights had no earth so now we can only use double insulated fixtures and plastic light switches etc.

 

[333rocky333]

It can be relatively easy, just take note of how the old cable threaded through the lamp
Dont steam in and pull out the old cable, you may need it as a draw wire to pull the new cable in.
Dont mess around with inline switches in the cable, if you want a switch use a lampholder with built in pushbar switch, there a bit more fiddly to put on though.
There should also be some means of restraining the cable in the base, so if pulled it dont strain the wires in the lampholder.
If possible post some pictures of the fitting and the lampholders you have

 

[333rocky333]

Ah, the whole house, built 1965 , is spurs, no ring. The work was subsequently checked by the qualified electricians who came to put a new spur in for the kitchen when it became apparent that the work was beyond me as there was the type of fuse box under the stairs that used fuse wire and they put in the sort that trips out with trips for each main spur. The socket spurs had been redone in the 90s and were ok but sadly the lights had no earth so now we can only use double insulated fixtures and plastic light switches etc.

Sound like whats known as RADIAL circuits rather than spurs, if its been checked, its likely ok so dont worry about it too much.
A spur is usually like a branch of a ring main and theres limitations, not allowing 3 sockets, but im sure thats not what you have

 

[Wilska]

Ah yes, radial not spurs, my knowledge of terminology is very limited. I will post pics

 

[Wilska]

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[bernardgreen]

Given the sharp bend the cable will make at the bottom of the tube I would fit one of these ( or similar ) to protect the cable from abrading on the edge of the metal tube.

Use the metal lamp holder and ensure the metal tube is continuous metal from top to bottom.

 

[333rocky333]

That looks a bit tight to bend 3 core round and through the base tube, do you possess any tools to trim a bit more of the threaded bar , I would guess it was flat 2 core cable previously.
I would opt for the metal holder as its stronger

 

[Wilska]

I was able to 'shorten' the threaded tube by adjusting the nuts' positions on the threaded tube:

Then theres extra tube at the top which is swallowed by the internal thread of the "shell case" at the very top:

Its solid now, no wobbles.

My current concern, having realized to use metal lampholder (thanks for advice folks ) is how the cable is clamped, is there a bit missing? :


@ Bernardgreen: the tube is continuous. What are the plastic fittings called you posted pic of please.

Regarding cable, the smallest hole it must pass through, the "shell case", has diameter hole 7mm. I'd like gold colour cable really, as is traditional with brass lamps.

 

[bernardgreen]

Various names

tube end grommet
tube end bushing
conduit end grommet
conduit end bushing