Grommets and 10mm Hollow Threaded Tube

OnlQQker · Sep 3, 2024

Hello everyone,

I'm currently making a table lamp out of driftwood found on the beach.
Does anybody have any ideas about the cable passing through the 10mm threaded rod regarding grommets.
I'm wondering whether I should use 3/8 BSP to 15mm plumbing connection to get me into a wider diameter.
Rope cable is rated at 700w so the bulb will be nowhere near that amount.

Any help here would be greatly appreciated!
I've attached some pics and thanks in advance.

[ElectriciansForums.net] Grommets and 10mm Hollow Threaded Tube

UNG · Sep 3, 2024

OnlQQker said:
Hello everyone,

I'm currently making a table lamp out of driftwood found on the beach.
Does anybody have any ideas about the cable passing through the 10mm threaded rod regarding grommets.

If you treat the threaded rod as a conduit as long as the internal ends are cleared of any swarf there shouldn't be a problem, you could use some heatshink tube to grommet the end if you wish

OnlQQker said:
I'm wondering whether I should use 3/8 BSP to 15mm plumbing connection to get me into a wider diameter.

I'm not sure what this would achieve other than changing the look of the finished lamp

OnlQQker said:
Rope cable is rated at 700w so the bulb will be nowhere near that amount.

I would suggest some sort of cord grips or cable saddles to secure the cable to the base plate to prevent the cable being pulled on the lampholder connections

James · Sep 3, 2024

I cant see a problem with the cable passing through the rod, presumably the end is not sharp, has been chamfered or similar.

the only thing i might do differently is where the cable passes across the base and turns up the hole.
i would drill a hole at 45 degrees about an inch from the centre hole so the cable goes round 2 off 45 degree bends instead of 1 tight 90 degree one.

Also, some strain relief on the cable just before it exits the base would be a good idea, could be as simple as a small plate screwed over the cable to compress it a bit into the wood.

edit;
@UNG seems to have beat me to it with an almost identical post!!

OnlQQker · Sep 3, 2024

Many thanks,

I will re drill the angle for the cable, debur the internal tube with a round file and add heat shrink, then search the web for some cable straddles.

Thanks so much for the help/guidance! @UNG and @James

UNG · Sep 3, 2024

OnlQQker said:
Many thanks,

I will re drill the angle for the cable, debur the internal tube with a round file and add heat shrink, then search the web for some cable straddles.

Thanks so much for the help/guidance! @UNG and @James

For the straddles you could use an offcut of pvc mini trunking lid or capping to make you own only needs to be like the cord clamp in a 13a plug

DefyG · Sep 3, 2024

These may be able to help!

www.lampspares.co.uk

OnlQQker · Sep 9, 2024

Finally put it all together and tested cables for continuity back to the 3amp plug.

My daughter now wants it lol, so I'm going to have to make another one.

But something I noticed when testing, is the one prong is live in the bayonet when the bulb is removed, I tested other lamps in the house and noticed this is how it must be..

So I've decided to switch to 12v, using a transformer like this

With some bulbs like this

Wired into the same type of bayonet I started with.

Does anybody see any potential problems with this?

This is what the finished lamp looked like, I'll have to go back down to Porlock Weir and get some more driftwood now lol

littlespark · Sep 9, 2024

Is there a switch on the flex, or a switch in the lampholder that you can sometimes get?
If not, then that’s why there’s a live showing when lamp removed.

12V would be much safer, and you would only need a 2 core flex, as there’s no earth required. Easier to pass through the 10mm rod.

You can buy cheap enough cable to fit the outlet on the power supply…. Any old cctv PSU and cable

OnlQQker · Sep 9, 2024

littlespark said:
Is there a switch on the flex, or a switch in the lampholder that you can sometimes get?
If not, then that’s why there’s a live showing when lamp removed.

12V would be much safer, and you would only need a 2 core flex, as there’s no earth required. Easier to pass through the 10mm rod.

You can buy cheap enough cable to fit the outlet on the power supply…. Any old cctv PSU and cable

I ordered a bayonet with a switch. To be honest I assumed (wrongly) that the prongs in the bayonet only became live when pushed down. Yet I do have an hazy image of putting my fingers into one of these when I was a kid...

I'm trying to research whether I can run 12v from transformer, up the existing cable. There's not much information on this so might have to run some tests.

Avo Mk8 · Sep 10, 2024

Did you get one of these: ElekTek Safety Switch Lamp Holder Half Inch Bayonet Cap B22 With Shade Ring Wood Mount Brass - https://www.buyitbetter.co.uk/products/elektek-safety-switch-lamp-holder-half-inch-bayonet-cap-b22-with-shade-ring-wood-nipple-brass?
This one won't let you switch on without a bulb in the holder. Can be found at various prices elsewhere.

OnlQQker · Sep 10, 2024

Hi @Avo Mk8

Yes I've got one of those, the thing is I've never made a table lamp before, so I don't want to give away something that I don't feel is safe, I know shops sell table lamps without a worry, but I can't do much abut that!

What I really don't like is the live prong. Everything is fine until somebody removes the bulb, think it's then switched off, and somebody else like a toddler, sticks their fingers in the top.

I did look at RCD rewireable plugs, but those plugs are quite chunky.

12v is the way I'm going to go, I never realised how far the bulbs have come.

.

Avo Mk8 · Sep 10, 2024

OnlQQker said:
What I really don't like is the live prong. Everything is fine until somebody removes the bulb, think it's then switched off, and somebody else like a toddler, sticks their fingers in the top.

Just to say that the description of that safety bulb-holder does confirm if you take the bulb out, the pins are not live, even if the switch is left on.
to quote:
The unique safety feature ensures that whenever the bulb is removed the exposed terminal brass plungers are cut off from the live supply.

I agree, from a safety perspective you have a duty of care, and for mains products doing something like an ISITEE (PAT as was) test and recording the results should be a minimum.
Using an already approved low voltage supply should relieve you of responsibility for electric shock

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