Thanks Sean and drpepper for the kind words! Drpepper, could you share a bit of your design? I'm curious!
So I'm still working on the keyboard, and I started with the naturals.
I bushed all the fronts with 1mm strips of actual bushing felt, using small amounts of regular wood glue and homemade wooden cauls to clamp the bushings. The narrow parts of the cauls are actually 4,1 mm, so that should leave a very small amount of play with the front rails pins which are 4 mm. I had to fine-tune all the front key mortises with a mortising chisel and files, so that the cauls would fit perfectly (snuggly but not too tight). I also have different bushing felts rolls in increments of 0,1 mm in case I file a little too much and there's too much play.
Then I worked on the key buttons. The Wurly 200 doesn't have key buttons, but I decided to use these as it makes things easier. I first routed 1mm grooves on both sides of several cross-grain rails. These grooves are cut so that the felt sits flush with the top and bottom surfaces of the buttons.
Rounding-off the fronts and backs of the button rails, using the belt sander.
Marking-up the positions of three 5,5mm holes for drilling the mortises on the drill press.
Drilling the mortise. Using a drill to cut the mortises is not the best, I thought about making a homemade tool for this, consisting of two chisels glued back to back to ensure the parallelism of the mortise, but ended up continuing with the drill press as I got quite good at it. Drilling the mortises instead of cutting them leads to more fitting afterwards, but I'm fine with that.
And then cutting the key button on the table saw using a crosscut sled and a stop-block.
Then I bushed all the key buttons, using the same procedure that I used for bushing the key front mortises.
I was a little nervous about gluing the key buttons without knowing if the naturals where running perfectly perpendicular to the front/balance rails and level with the keybed, so I made two reference rails with pencil marks on both the front and back of the keys.
These rails are nailed directly into the keybed.
Gluing the key buttons. I used wood glue and a few drops of CA glue to hold the buttons in place while the wood glue dries. I had to press on the buttons with my fingers for about 5 seconds, which is enough for the CA glue to bond, then remove the key from the rails and clamp the key button to the key with a spring clamp.
Then trimming-off the key buttons flush with the keys using a hand-plane.
So I almost finished to glue all the key buttons to the naturals, and reamed a little bit of the keys balance holes to limit friction. I'm a bit worried because this morning I noticed that I had quite some play in the keys in their up-position (not pressed), and I can't find info about what is an acceptable amount of play in the key bushings and key buttons. I guess as long as the key are not rubbing against others, it's sort of ok, but it'd be best to know what is the standard amount of acceptable play, so if anybody can shime in that would be great!
Right now I have between 0,6 and 0,7 mm of play in the naturals (which is a tiny less than 1/32 inch for american friends), measured at the back and front of the keys, in their not-pressed position. Does that seems too much? I have to say that I still didn't polished the pins, which I should have done before bushing everything, damn me%u2026 and I also don't have an acoustic piano around to compare.
So, should I rebush the keys front mortises and key buttons using 1,1 or 1,2 mm felt instead of the 1 mm I used, or is 0,7 mm of side-to-side play in the keys acceptable? Theoretically 0,7mm is too much, as I only have 1mm of clearance between each key. Here's a link to a video showing that:
https://youtu.be/mEnoQPDt0o0I also have to mention that it's winter, so the wood of the keys might shrink a bit when summer will come, and therefore tighten the mortises a bit. Should I take that into consideration? I also guess there's a bit more friction in a brand new keyboard than one that has been played for years. I'm pretty ignorant on this subject, so if any of you experienced piano tuners could enlighten me, I'd be very grateful!
Wish you all a great sunday!
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