Tap & die

[Muggins2003]

Hi!

Is it possible to get a tap n die to produce a working screw and tubing with threads to match in sterling silver? I don't seem to be able to get it to work - not sure if it's the quality of the tap n die set or whether using silver is the problem.

Any advice would be great!

[Dennis]

I know what you mean. Accuracy is imperative for instance by matching the die used for the screw to fit exactly to the tap for the tube.

Ideally the tube is clamped to the head of a mini-lathe and rotated manually while advancing the tap held in the tail stock. Failing that the tube should at lest be held in a safe jawed vice, while turning the tap in a pin vice.

Once the tube is threaded, it's the turn of the screw. Check that the tap you used will fit the die for the screw. The material for the screw should be perfectly straight and preferably 9ct white gold rather than silver, or it will quickly wear. Fix the screw material in a vice and carefully turn the die on it.

In both cases use oil as a lubricant and reverse repeatedly to shed the cuttings.

In many cases it is possible to dispense with this problem in silver and soft metals by by forcing a steel or stainless screw, such as is found in old electrical items or spectacle repair kits into a slightly undersized hole, so that it cuts its own thread.

Dennis

[Muggins2003]

Thanks Dennis,

I seem to have the screw made ok. However, I was holding the tubing in my hand while turning the tap in a pin vice. I will put the tubing in a vice and try again. I was applying lubricant but the end result was the screw going straight through the tubing without any need to screw it in despite using the same size tap and die to produce the screw and tubing.

I will give your suggestion a go and see how i get on. Somebody else recommended white gold but i'm hoping to get the piece cast and my understanding is I therefore need to use just one metal (and the rest of my design has been made in silver).

Thanks - will try again with the tubing held securely

[Dennis]

Hi 2003,

The trouble with silver screws is that the material is not suitable and the thread will slacken almost at once. The problem is not as serious for a permanent cold connection, but they will not survive repeated use.

The only thing against using a gold screw is that your piece will still be hallmarked as silver. Dennis.

[Muggins2003]

Hi 2003,

The trouble with silver screws is that the material is not suitable and the thread will slacken almost at once. The problem is not as serious for a permanent cold connection, but they will not survive repeated use.

The only thing against using a gold screw is that your piece will still be hallmarked as silver. Dennis.

Thanks Dennis - i was hoping to get the piece cast so not sure a really small screw and tubing can be cast because the clean-up would probably result in threads being worn. My head is wrecked - if anybody has any ideas on how to get this type of idea to work - they are very welcome to share them : P

[Dennis]

The problem with this conversation 2003, is that it is taking place under a blanket; a blanket of secrecy, that is. If you were to disclose what exactly you are wanting to make, I am sure one of us would have the answer.

BTW my first port of call for agate disks would be AE Ward & Son. they are in Clerkenwell, London and I would phone them as not everything they do is on their web site. Dennis.

[Muggins2003]

The problem with this conversation 2003, is that it is taking place under a blanket; a blanket of secrecy, that is. If you were to disclose what exactly you are wanting to make, I am sure one of us would have the answer.

BTW my first port of call for agate disks would be AE Ward & Son. they are in Clerkenwell, London and I would phone them as not everything they do is on their web site. Dennis.

Sorry Dennis - i wasn't purposely trying to be secretive. Apologies if i annoyed you - last thing i wanted to do.
I'm trying to connect a thin layer of silver fretwork to another thin layer of silver fretwork with either acrylic or agate in between without using rivets as it will take from the design and will be tricky to put together without wrecking it.. By using only 1 big rivet through the middle, my fear is the front will spin so I was thinking that a small tap n die might work. I was hoping to get the pieces of silver with the connecting pieces (screw or pin) cast so that i wouldn't need to solder after casting .

Thanks for agate contact. Will give them a bell tomorrow.

Thanks again for your help

[Goldsmith]

Threads would be better done after any casting, has anyone ever explained the fact that cast items can shrink slightly in size from model to casting, in simple terms this would mean that threaded wires would cast thinner than the pattern and threaded holes would cast wider than the pattern as it is the metal that shrinks. Therefore any threads and screws would be looser than the pattern after casting. For tiny threads of circa 1mm. I use Bergeon watch taps and dies. For larger jobs I use BA taps and dies, from 12 BA upwards.

James

[Dennis]

Sorry Dennis - i wasn't purposely trying to be secretive.

No I was just kidding. Cast tubing will crack rather than spread, so I think provided you can drill the centre material of your sandwich and line everything up, then a minimum of two soldered tubes is the way to go.

To fix the rivets, you can:

1. Countersink the outer hole and spread the rivet with a scriber without hammering. If necessary you can weaken the tube by drilling a little way into it.
2. You can use well chosen stainless steel screws from a glasses repair kit or opticians suppliers.
3. With or without item1, you can glue in a small decorative head with a well fitting stem to hide the tubing, using two part epoxy, such as five minute Devcon from Cooksons. If you don't want to make you own tube closers, you can buy in headed ear posts or ball studs, meant for earrings.

Below: Supporting a tube for soldering with a short piece of wire.. Dennis.