bizibilder
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Sorry for being so slow to reply! In answer to your question about my "tube" method of holding square stuff in the lathe - you simply tighten the chuck or collet enough for the round tube to close onto the four corners of the square (or rectangular) workpiece. It should just grip on the corners. The brass "tube" remains round - just a couple of thou is enough to close it tightly onto the square stock. You would need to make a new brass "tube" for each size of square or rectangular stock.
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I wouldn't bother with the four jaw at all - make a thin walled tube from brass that will just take the rectangular pieces within itself. Cut longitudinally through the tube wall in one place (use a hacksaw and files as you need to be able to close the tube slightly). Put the tube in the three jaw (or, preferably, a collet) and tighten up. The pieces will be held dead centre every time. That is how clockmakers hold square or rectangular stock for machining. Another trick is to get some plastic tubing (unused fuel tube or windscreen washer tube for motor cars) and cut 1" lengths of them. Slice a strip out of them longitudinally so they can "close up" and use them in the three jaw to hold round timber for masts and spars. Result is a secure hold and no marks at all on the timber.
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Virtually all taps and dies are made for RH threads and they are usually not labelled. LH taps and dies are specials and will normally have "LH" on the stem along with the thread size. However there are many taps and dies that have no information on them! This will give you tapping sizes (ie the size to drill a hole to be tapped): http://www.shop4fasteners.co.uk/acatalog/UNC-Tapping-Drill-Sizes.pdf For rod to be threaded the nominal size diameter is the one to pick. Ie for a 6mm thread use 6mm rod (which will always be a little undersized anyway).
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Cutting/Sanding Brass?
bizibilder replied to esion's topic in Metal Work, Soldering and Metal Fittings
Files are the tools to use for shaping and finishing brass (or other metals). Abrasive papers are really only for finishing and polishing. A useful trick when making small brass parts is to leave them attached to the "parent" stock so that you have something to hold whilst working on them. Sometimes with pre-made parts, especially if they are very small, it could be worth soldering them to a big "holding piece" to work on them (or epoxy/glue/tape them if you don't like soldering). When complete you can un-solder them (or break the epoxy bond) and file them clean before you use them on your model. -
If you want to get silver solder to flow into the joints then you need flux and silver solder in wire form (not the paste that you are using). Flux the end of the wire and the inside of the hole (Flux powder is mixed with a little water to make a thin paste). Make a tiny ring of solder wire and assemble the three parts (pin, hole and ring of solder wire) heat with the blowtorch and when the solder melts it will run wherever you have the flux i.e. inside the joint. There must be a tiny amount of room for the solder to get into so a "loose sliding fit" is what to go for - alternatively just file (or saw with a jewellers saw) a couple or three tiny "nicks" around the inside of the hole to give the solder somewhere to go.
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If you want free cutting brass then the grade to use is CZ121 (in the UK). This is supplied as flat bar, round bar and hexagon bar. If you want sheet (up to about 6mm maximum thickness) then the grade required is CZ120 called "leaded engraving brass". These can be obtained from horological supply houses or engraving suppliers. When machining these brasses you should use a flat topped lathe tool and no lubrication. The shavings will come off as a stream of fine particles. For drilling, as mentioned above, you should remove the sharp cutting edge from the tip of the drill so that it scrapes the brass as it cuts.
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Florists wire may not take too kindly to a sharp 90° bend. Maybe try brass wire and heat it to red and then allow to cool, bend it and use a light hammer to persuade it to go 90° over a sharp 90° block. It can be painted or chemically blackened to look "right".
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Neat idea
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