Dave Leggett Posted June 18, 2019 Share Posted June 18, 2019 (edited) CASTING REED FRAMES In constructing a few instruments of my own, I had always used reclaimed Lachenal reed-frames, suitably cleaned and refined. I had been given a large quantity of these by a friend years ago and acquired more since. Many that contained damaged, missing or brass tongues could be bought very cheaply. Modern wood-saw blades have been a source for my reed-steel. I intended to make a Baritone Anglo. As this was to be pitched a whole octave below a standard C/G and reed frames of a suitable size for the lower notes are not easily obtainable, I had to reconcile myself to making them. I reckoned on having to make 1x reed frame for 50mm tongue-length, 2 for 45mm and 6 for 40mm. I was quite happy to fret-out the 3x larger sized ones from 2mm brass sheet but the 6 at 40mm were enough in number to justify making a casting-pattern in brass and using this to 'sand-cast' them. I would be casting in a bronze alloy using Delft Clay as the casting medium. As a working jeweller, I was already set-up to produce small castings in sterling silver using this technique. I experimented with alloys and found that 75% Cu: 15% Ag: 10% Sn gives a brassy-looking alloy that melts in an achievable range, (about the same as sterling silver: ca. 850-900C) and works amenably. The castings would have to be fettled, of course but if done thoughtfully, both the dovetail bevel and the slight flaring of the slot from front to back, included in the pattern, may be achieved as integral with the casting process. The idea of casting reed frames may seem a bit 'academic or old-fashioned', particularly in a role where CNC machines have taken over the territory traditionally occupied by precision press-tools. I hope that the appended images will give any explanation you might want, that I haven't included in the above text. KEY TO IMAGES 1) Lower half of casting flask (the drag) 2) Upper half (the cope). Both contain the compacted and levelled 'Delft Clay' and show the impression left by pressing the pattern - flat, top down, (with a board) into the drag. Clay has been removed to a depth of 1.5mm from the drag reed-slot using the 'hag's tooth' tool (7, below) before the cope is applied and re-compacted. Release material is talc. 3) Low 'C' reed': 50mm in length, in frame fretted from brass sheet. 4) Low 'E' reed: 45mm in length , in frame fretted from brass sheet. 5) Casting pattern for 40mm reed frame and clamp plate. 6) Low 'G' reed in bronze frame: cast using (5) as pattern. 7) The 'Hag's Tooth' tool, with tooth 2mm x 1.5mm: simply made from sheet brass. The final images show the finished 'Baritone' with normal sized Anglo for comparison. Edited June 18, 2019 by Dave Leggett Title omitted originally! 3 1 Quote Link to comment Share on other sites More sharing options...
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