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4th March- Steve Giles

7 March, 2013

Steve Giles – Metal spinning and Resin work

Soft metals like pewter and copper can be moulded around wooden formers when spun on a lathe. The technique is within the capability of most woodturners, though some new tools are needed to form and burnish the metal. Well we all like an excuse to buy tools, don’t we?

2 Spinning tools
Spun metal items can either stand alone or act as decorative or functional inserts for turned wooden things.
Steve started his demo with a pewter disc clamped between a bowl-shaped former at the head of the lathe and a block at the tail end. A curved forming tool was levered against the disc as it spun using a steel peg in a bar in the tool rest as a fulcrum. This stretched the metal to force it into the shape of the former. An additional “tool” is a wooden wedge held between the metal and the former. This is withdrawn as the gap closes and is necessary to avoid what would otherwise be the unsupported edge going wavy.

1 Steve, spinning    3 Spinning operation

Steve demonstrated what happens without the wedge. Some of us thought the resulting wavy edge was quite attractive!
The stretching is unlikely to be uniform so the edge needs trimming. Turning tools will cut pewter quite easily so trimming can be done with the point of a skew chisel at right angles to the surface of the formed metal whilst the wooden former is still supporting it.

4 Spun dish, pewter    5-Spun dish, wavy edge

Copper can also be spun though it requires rather more pressure and tends to heat up. This would cause it to harden so regular dunking in water is required to anneal it to keep it ductile.

The second part of Steve’s presentation was a talk about using coloured resins. He had drawn a pattern of lines on paper which he stuck on a bowl blank and cut it into pieces along the lines. The exposed surfaces had been sealed with clear resin to prevent the subsequent coloured resins bleeding into the wood. The pieces are then stuck back together with coloured resin, often with (tile) spacers to define the thickness. The re-assembled blank can then be turned as a normal bowl.

6 -Unfinished Resin bowl

The resins Steve was using are epoxy, coloured by the addition of a little artist’s oil paint. Mixing of resins with hardener can introduce air bubbles. Steve doesn’t usually see this as a problem. The removal of bubbles is possible with vacuum systems to suck the air out. This is a tricky operation as the resin tends to erupt as the bubbles expand under vacuum. Some claim vibration can be used to release bubbles but Steve doubts the efficacy of that method. Polyester resins can also be used. These are more brittle but are less prone to the retaining bubbles.

The subjects covered were clearly novel to many of us and a high proportion of members had turned out to see what it was all about.

After Steve’s presentation, John Davis kindly gave a critique of the members’ gallery. There was a good display on the gallery table and pictures can be seen on the website.

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