Edison thread tap

Michael,

You are correct about ali being a good insulator in its raw state due to the oxide build up. However there are coatings and anodising treatments that allow good conductivity. I suspect Jason's edge finder and mine for that matter are coated. We used to use Alochrom and later a altermative that provided an acceptable bond for EMI gaskets and grounding points within comms equipment. It was important to ensure that the surface was throughly cleaned before assembly. Bonding points should not use any type of washer that could break through the coating, if it did it would soon fail insulation checks due to oxide build up, if the joint was not airtight. I have seen bonding points that have used serrated washers that have then been coated with grease that seem to work.

Hugh

Michael Gilligan:

Thanks for the interesting Sumitomo link - I had no idea they were into this kind of thing although they know a thing or two about steel.

J Dewar McLintock professed to be "hooked" on the Dauphine and has a good deal to say about it in his book about Renault including the gift of one to the Queen which was used by her and the Duke (!) at Balmoral.

[with apolgies for drifting so far off-topic]

.

ega

I think the handling characteristics of this one could be 'interesting'

**LINK**

https://www.lanemotormuseum.org/collection/cars/item/renault-dauphine-henney-1959

MichaelG.

.

Edit: perhaps it's O.K. 

There are batteries in the front as well as the back !!

Edited By Michael Gilligan on 31/07/2019 18:36:32

If you've ever seen electricity pylons marching across the landscape, the cables are usually aluminium with a steel reinforcing core.

en.wikipedia.org/wiki/Overhead_power_line#Conductors

Neil

Would something like what we used in skool be of use ?

The Interwebnet is full of choice eg. http://catalog.miniscience.com/Catalog/Electricity/Lamp_Holder.html

.

I'm aware of that, Neil ... but thank you

The problem with Aluminium is not its conductivity, but the comparative difficulty of making good terminations.

... By no means insurmountable [and ultimately very worthwhile on long cable-runs], but not to be taken casually.

MichaelG.

I remember being impressed or should that be amazed with the 'slenderness' of the gear-change lever on the Dauphine and its sister the stylish Floride - thin as a pencil, taking economy of materials beyond BL levels.
DaveD

**LINK**

https://www.connectorsupplier.com/design-considerations-when-terminating-aluminum-wire/

[quote]

• Oxides form an insulating layer – Aluminum forms a dense and very hard oxide layer on the wire surface. The contact design and termination process must fracture these oxides to provide an excellent metal-to-metal contact.

[/quote]

OP, couldn't you just take the guts from an ES lampholder (the screw part) and insert that into whatever you're making?

(As I probably cannot assume that you are all men and so as to avoid any offence to the ladies, I'll refer to you collectively as 'Members' - for the sake of PC, you understand)

Members,

I am overwhelmed with the responses and ideas. Firstly to suggestions of using a socket, this deviates from the KIS principle (an earthed plate to hold lamps). Sockets require riveting/soldering and the density precludes them.

Michael's idea of electro-forming is interesting. An additive process - juices flowing! - so why not EDM? An EDM machine is on the bucket list (the one by Langlois from HSM), but far into the future.

I like the idea of making a tap and will use it on copper, instead of aluminium. Thank you, everybody.

(BTW, can someone please change the spell-checker to be UK English? - even tho' I'm not)

Hi All,

FWIW, on film sets these days, (and for some time) the large diameter cables used for film lighting are all made of aluminium, purely to save weight.

Film sparks are usuaully of large build and still sometimes struggle to carry the larger length cables used on location. How they ever managed with copper I cannot say.

How they manage the terminations when used in alll weathers again I do not know.

Cheers, Martin

The trick is to make a solid metal-to-metal connection by welding or a proper crimp. Done properly Aluminium is serviceable as a power conductor. I've come across electric motors wound with Aluminium wire. Sometimes done to reduce weight, sometimes to reduce cost. The connections looked welded to me.

Aluminium has been tried for cheap domestic wiring but got withdrawn because of the fire-risk. When connected to ordinary screw terminals in wall-sockets etc, the joint tends to corrode, go high-resistance, get hot, and start fires. Or fall apart. If the electrician tightened the terminals 'just so' the risk is low, but terminating Aluminium is far less forgiving of mistakes than Copper. For the same reason, I think Aluminium is a poor choice for a lamp-socket. Over time the lamp to holder joint will tend to become unreliable.

Hugh's idea of using Copper may be a poor choice for another reason - Copper is hard to machine. It's prone to tear. If the thread is to be cut with a tap or on a lathe rather than moulded, I'd go for Brass. Not such a good conductor as Copper, but mechanically stronger and much easier to cut. Brass to Copper contacts corrode very slowly.

Dave

Dave,

Michael's suggestion not mine.

Hugh

.

Hugh,

Michael's suggestion was to electroform it from copper, not to use a tap.

... and incidentally [both Dave and Hugh] I believe Phillip was talking of thread forming, not cutting.

[hence my question to Jason when we were discussing Aluminium]

MichaelG.

Best answer then, If you could get it in one of the lower tempers it would form easier than in say T6 but should still be ductile enough to use a thread forming tap.

.

Thanks, Jason

Probably water-under-the-bridge now ... but at least we have the answer for future reference.

MichaelG.

Quite a few ES holders are actually made from insulating material. There is a leaf spring that contacts the centre pin and a slot in the side of the insulating female portion of the thread. Through which a second leaf spring contacts the side of the ES cap. The mains is simply connected to the two leaf springs.

Andrew.