I need to make a couple silver screws wondering if the CNC could make them?
Hi Dorine, I’m not 100 that the cnc isn’t of use here but I think the better tool for such an application is the metal lace.
@metaltechs what do you think?
Our current lathe is not up to the task (the Colchester from SMEE will do it) but a thread mill on the mini cnc should be able to manage it. It’s an advanced operation with special tooling that won’t come out as nice as a turned one but based on the photo, I’d think it’d work.
I’ve got a few questions:
I am guessing from the photo that these are going to be quite small? What kinda size are we talking?
Do they thread into anything or are you making the receiving part as well?
Do you already have a part that you just want to thread or are you looking to make the whole thing on the CNC? If you want to make the whole screw, what does the stock look like?
I think based on the answer to those it will probably steer you towards a solution.
I am guessing from the photo that these are going to be quite small? What kinda size are we talking?
These are tiny about 10mm long by 3 mm ish…
These are 1960’s (my mums) Silver hand made foot bangles
Do they thread into anything or are you making the receiving part as well?
they fit in the socket that the bangles have but long lost
Do you already have a part that you just want to thread or are you looking to make the whole thing on the CNC?
Just the screw part although it might not be a screw rather a bolt…?
If you want to make the whole screw, what does the stock look like?
Not sure what you mean by “the stock” not a term I know yet in this context 
By stock I just mean the raw material 
how it looks will help you choose which tool is best for making the screws.
The CNC maybe it able to do it, but it also maybe overkill, at least for threading the nut and bolt . A die for m2.5 or something like that will probably do that no problem (although I’ve never tried to tap silver…) and you won’t have any more advanced operations to do (unless you want to learn how to do those of course).
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Ok so 925 silver would be my stock.
Would it be better if it was a flat sheet or rod?
Would it be better if it was soft (Annealed) or hardened (pulling metal rods to make them thinner hardens them)
This is much smaller than I imagined. I was gonna ask if anyone knew how well silver takes to a die. The receiving thread is the critical question now. Can you post a picture of the existing hole? If the thread already exists, trying an existing fastener is probably the best way to figure out what you’re dealing with (but it might’ve bent over time). If not, you’ll need to make sure you’ve got enough material to make a meaningful thread. Silver is obviously a lot better than gold here but I’m still a little skeptical.
I can bring them in with me on Wednesday, Ill be there from 3-9pm if either or both of you are planning to be there?
I’d consider starting by getting an impression of the thread and making a cast using something like whitemorph thermoplastic (granules become like putty in hot water, but then sets hard). With beeswax or release agent, that should then screw out, giving a plastic version of the screw. There are then various possibilities- making a mould for e.g. lost wax casting, or giving model to 3D scan for two sided cnc, specialist 3D printing in metal and silver plating etc. It could also help you possibly find a piece which has close enough match. You might find something close enough in the tap and die set in the space, then could use the metal lathe for the unthreaded piece.
I’ve tried 2 sided CNC. I think getting exact registration, depth match, and touching off which would be needed for this would be a massive challenge.
Perhaps ask for help from SMEE?