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Bechstein B, pinblock inserts

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Here the frame has been raised slightly. Underneath you see the pin-block in 3 different states. In the top section, the positions of the old holes have been marked with a papor rubbing. Next morning I got some mylar sheet.
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Testing drilling the tuning pin holes. The vice is set at an angle of 4 degrees. The block of wood is a test insert.
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The test insert has been drilled, and later I'll check that the holes are right, by replacing the frame. You can also see in the cut-out for the next section. I started with the top two sections, as the shape was square. The little marks at the bottem of the cut-out are from the old tuning pin holes.
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The finished inserts have a channel cut into them, 4mm thick and 10mm deep. There is an equvalent channel routed into the main pin-block. When the epoxy is syringed into the joint, it forms a strong key. The force of the strings on the pin-block is such that it wants to tilt the insert forward. These keys aid in resisting this force. In addition there are
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Here you see the mylar sheet used to record the tuning pin hole positions. The pine-wood platform is there to support the router.
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Part of the tenor cut-out can't be routed, as it comes to close to the edge. Not too close structurally, just that the router base is too wide. So I've chiselled this part out.
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... ditto
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Finished chiselling. Note the plywood piece made to guide the router.
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The completed tenor insert, with the marks for drilling the tuning-pin holes transferred from the mylar sheet. A pencil line is drawn throught the mark, and this is aimed at a fixed point on the drill press, to keep the 4 degree angle consistent for each unison.
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There's the platform for routing the bass section.
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Marking the hole positions for the bass. The marks don't appear to be in the centre of  the holes, because of the camera angle.
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... that's more like it.
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Here's the router in action. I went out and bought a new router especially for the bass section. I had to modify its base, so that it could get in closer to the edge.
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The modified router base is narrower, allowing for closer access.
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The platform has a curve marked on it. I transferred the curve with a mylar sheet, to another piece of ply, to use as a guide for the router. Although the router got in close, I had to do some chiselling by hand.
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... some saw-dust.
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... the tenor insert in its cut-out.
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Radiata pine test piece, used to practice making the real thing.
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The glue and mixing tray. This epoxy resin is very tough.
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The top three inserts about to be glued. They've all been drilled out. The Soprano insert is covered in masking tape as I don't want the glue to seep into the holes.
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... detail. The faint pencil lines are there because it's refined to have the backward slope of the pins point to the agraffe, instead of having one straight-ahead angle for all the pins.
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The soprano insert glued in. Tightening the clamp forces some glue onto the insert ... hence the masking-tape.
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I chamfered the top of the insert sides to make a V-channel, and as some glue penetrated the old timber, I used the syringe to top up the level. Fortunately the glue takes about an
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Now Soprano and Alto inserts are glued.
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... ditto ...
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... and the Tenor insert.
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All dry, and I've sanded away any excess glue. Beside the pencil sharpener and the drill, there's a round plug with a tuning pin in it. That's to test the size of the hole that will suit this particular timber.
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This is a piece of pine, made as a test for the real thing. The shape has to fit snugly, so once I get the dummy right, with soft wood, I can use the knowledge to get the real insert right.
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So there's the real Bass insert, drilled, and covered with masking-tape. There's plenty of glue there, some of it will seep into the joint.
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All 4 sections done, dry and sanded.
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 .... ditto ....
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 .... ditto ....
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Record of Pin-block replacement on Bechstein B s/n 124436. The original plan was to replace the whole pin-block, following the advice of David Jenkin. However David didn't seem to be 100% certain that the process conserved the tone of the piano. He said the piano he replaced the pin-block on was an old one which he did up for a friend to have in his weekender. I decided not to risk the tone of this gem, so I have provided new pin-block material inserted into the old plank.
 

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