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cutting spiral/helix

I need to cut a spiral onto a silver rod. The sides of the cut can be at 90 degrees/and/or inclined. I envisage this to be done by a lathe (milling machine?). Diameter of rod could be 10-15mm, spacing between edge of the next groove ca 3mm, groove width & depth ca 2mm (ideally there should be some scope for visual considerations). Non electric system would be acceptable (or very slow speed lathe), machine size should not be more than 1m, weight under 50kg. Cost should not be more than $1000-1500, but this assumes that it can be used for other applications, eg cutting tool steel etc.

I once owned a wood lathe (used it a couple of times only) & have used a larger metal lathe under supervision for spinning. Metal lathe users sites are so full of intalk that it is difficult for a novice to decipher the essential info. Any suggestions?

I thought of buying a sherline - but are there cheaper options?

norwick

Reply to
norwick
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Any metal lathe with threading capability will do what you want.

You don't mention where you are, but one quick way to get an idea of what is available is to visit your local Harbor Freight store and look at something like this

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Very similar machines, with better quality control, are available by phone/Web order from Jet and Grizzly.

You mention cutting tool steel; these would be OK for *small* items in "friendly" varieties like O-1. If you do more jewelry-ish items a Sherline would be better - more relevant accessories available and still cheaper than a Boley or other 'real' jeweler's lathe.

As an aside, if your silver rod is more than a few diameters long you will want a 'steady rest' (fastened to the bed) or a 'traveling rest' (moves with the slide on the bed) to keep the rod from bending while you are cutting. Both types of rest typically hold the workpiece using 3 bronze bars that rub on the surface of the workpiece. Since bronze would scratch your silver, you might need to make a set of replacement bars - or at least add-on tips - from Delrin or other suitable plastic.

Reply to
Fred R

I think what you want to cut is a helix, not a spiral. 3mm pitch is going to take quite a lathe, a small one isn't going to do it with regular threadcutting gear and leadscrew. There's some woodworking routing jigs that could either be adapted or the idea stolen and reworked for use with something like a hand grinder and burrs. These use aircraft cable and pulleys to move the carriage back and forth and supply rotation to the workpiece. There are means for indexing the workpiece for multi-start helices, too. Sears used to retail one, I'm sure some of the other online woodworking outfits have them also. Looked like something that could be homebuilt if there were enough gumption on the part of the would-be builder.

Stan

Reply to
stans4

If this is a one-off, you could use a wood lathe (no motor needed), some cabling and pulleys, and a dremel tool. You would have to make a sliding carriage and/or mount for the dremel; figure out the pulley ratio and geometry; and make some kind of chucking arrangement for the rod, but with a bit of thought and some blocks of hardwood you could easily stay under $1K.

There are rigs made like this to use wood routers to cut all kinds of complcated helical shapes on table legs; yous is just smaller.

Reply to
jtaylor

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