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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.
Testing drilling the tuning pin holes. The vice is set at an angle of 4 degrees. The block of wood is a test insert.
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.
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
Here you see the mylar sheet used to record the tuning pin hole positions. The pine-wood platform is there to support the router.
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.
... ditto
Finished chiselling. Note the plywood piece made to guide the router.
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.
There's the platform for routing the bass section.
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.
... that's more like it.
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.
The modified router base is narrower, allowing for closer access.
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.
... some saw-dust.
... the tenor insert in its cut-out.
Radiata pine test piece, used to practice making the real thing.
The glue and mixing tray. This epoxy resin is very tough.
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.
... 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.
The soprano insert glued in. Tightening the clamp forces some glue onto the insert ... hence the masking-tape.
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
Now Soprano and Alto inserts are glued.
... ditto ...
... and the Tenor insert.
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.
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.
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.
All 4 sections done, dry and sanded.
 .... ditto ....
 .... ditto ....
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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