Thanks Tom, but occasionally there are frustrating lessons to learn.
A prominent feature of the wagons I model are clusters of six rivets on headstock channels, where each solebar connects. I'd made the channels and angle steel shapes by milling from
extruded brass bar, as it cuts so much more easily then
rolled sheet or plate.
However, when it came to embossing rivet heads in the brass of extruded origin, disaster - roasted chestnut rivets!
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Several new punches were tried, having a variety of different end angles and rounded/pointed ends - but to no avail.
Subsequent tests of these punches in brass and nickel-silver sheet metal showed no problem, and rivets heads formed well and didn't peel open. Then knowing how ductile copper is, some new channel was milled from 3mm thick sheet. Despite the copper becoming quite tough from work-hardening during the machining, rivet heads embossed easily without any need to anneal the copper.
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More channel was then milled from 1/8" brass plate, and this too, also embossed well. A check of metal grades and material usage recommendations in suppliers catalogues revealed why this should be.
To get the punch to fit inside the legs of the headstock channel, and to ensure good alignment of rivet heads, a jig was made to keep all tidy. The diameter of the punch is only 1.6mm below its shoulder. A short collar is slipped over this reduced diameter, which by adjusting its length, controls the height of the rivet head produced, when using a drill press.
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-Brian McK.