The method used here is based on guidance from shop owner and skills learned from North Bennet Street School. Each shop will have different ways to glue on bridge caps. Of course our method is not the best. At least it works.
There are locator holes drilled for #6 bridge pins before bridge was removed from piano. The holes need to be transferred to new cap. put a #6 bridge pin in each locator hole on root, hammer them down till bottomed up. trim pin tops so there is just about 1/8" length of the pins sticking out over bridge root surface.
Place new cap on root, flip upside down and clamp where the pins are to press the pins into cap and make marks. Pencil mark root shape on cap while clamps are on.
You can see the marks on cap. Drill through the marks and saw cap to the shape of bridge root. When sawing, leave 1/8" room out of the pencil mark just to be safe.
Remove bridge pins from root, make pencil lines everywhere on surface then sand until all lines disappear. This means the surface is mostly flat. Feel the surface with hands to make sure. Sandpaper used here is 80 grid out of personal preference.
Bend a razor blade, scrape root surface to make smiling face (hollow in middle). This will allow glue to stay for a sturdy joint. Same sanding and scraping on cap.
Wax some more #6 bridge pins, hammer them through those locator holes we just transferred. The pins will go through bridge cap into root. Put clamps on to dry fit, check if there is any gaps between root and cap. Adjust, dry fit again, and repeat the process till the joint looks gapless.
Mark the overhang at the two ends then sand or saw to flush.
Glue cap on the root now. The glue jig is crowned to replicate the crown of soundboard. Glue is SK-8 purchased from Mason and Hamlin piano factory in Haverhill, MA. tighten each clamp, then do another pass to make sure everybody is very tight. Clean glue squeeze-outs with hot water. Wait for 24 hours at least before unclamping.
The old pin block on this Mason&Hamlin AA does not hold tuning pins tight anymore. It will be replaced. The original one has 8+ layers of hardwood, possibly maple. We are able to make a 5 layer panel with wood grains 90 degrees between each layer.
Jude, the shop owner, and Ellie, our summer apprentice, milled and put together the five layers of hard maple. Since our press is small, the big panel is cut into two pin blocks, narrow on the bass and wide at treble.
The wood is placed into a cast iron tray, then the press. There's sufficient glue between each layer and between cross pieces.
Tighten the small piece of cast iron in front to push cross pieces tight together in the press. The air pumps push the pin block tight from top. One day we'll have a bigger air press so we don't need to cut the penal in half before gluing layers together. One day...
2 days later, the pin blocked is removed from press and let dry in room temperature. Five layers nice and tight. It doesn't look pretty for now. It'll look much better after milling in the future.
Before the soundboard is glued in, the beams are painted black for the sake of looking good. Why not. This was sprayed black by shop owner. Protect the rim before spraying.
Ellie is off school for summer vacation. She's help us big time in the shop. The glue used here is SK-8 purchased from Mason & Hamlin piano factory in Haverhill, MA. We bought 3 gallons out of their 50 gal container. In order that the soundboard is fastened extremely tight in the piano, dozens of clamps are used side by side all the way around.
24 hours later, the clamps can be removed. There are some gaps around the soundboard. We use WoodEpox colored by powdered pigment to fill the gaps. There is only sanding sealer on the surface for now. The board will be sanded and sprayed with a couple final finish, satin or gloss.
When a hammer hit strings of a note, for the max energy transfer, all strings of this note must be struck by the hammer top surface at the same time. Not all strings are at the same level/elevation/height. The hammer tops will need to be filed to achieve this.
sLift the dampers by pressing sustain pedal, lift each hammer to the strings by hook or other technique. The technique used here is learned from Mr. Don Mannino, head technician at Kawai Piano. Push up the jack toes to let-off button with two fingers so the hammer blocks the strings (shown on picture in the middle). Plug each string to see if anyone is ringing or not being blocked by the hammer. If ringing, that means the surface under that string is low, and the high surface needs to be filed/sanded down. Mark which side to file/sand on the key stick, one octave at a time.
With Cheek blocks in, mark location of the action/keyboard. So we won't need to place the cheek blocks in and out over and over again. Each time sliding the action out and in, the front stops right at the marks.
File/sand on hammer tops according to the chock marks. The sanding paddles are homemade with fine sandpaper. The mid picture shows a tool with a thin strip of sandpaper fastened on a piece of plastic. It is easy to sand for single string contact spot. The plastic allows us to see where we are reducing. Push action back to piano, recheck hammer to string fitting. The same note may be adjusted over and over again till all three strings of each note are blocked by the lifted hammers. Wipe off the chock marks when mating is complete so we don't confuse ourselves.
All better. The piano was then tuned by the shop owner Mr. Jude Reveley before customer came to inspect. Thank you Ms. Steinway L. Your cooperation and company is truly appreciated.
Locate the newly capped bridges via triangulation. The triangulation was down when the old bridge was still in the piano. The location data is transferred onto new bridge.
Mark the bridge location, double check with plate in, then use drill bit to locate soundboard button which will be screwed from the bottom of soundboard into bridge body. Some of the holes are for installing weight under bridge if needed. The weights may be added to improve sound quality.
Before gluing on the bridges, the board is sanded smooth. Limited on the press, we glued two smaller bridges, let dry, then glued on the big treble bridge.
Lastly, the soundboard buttons are installed to further fasten the bridge and soundboard together. Next, the board will be finely sanded. The shop owner will spray sanding sealer and finish on it.
Prep the surface of both bridge root and cap. Sand smooth with 80 grid sandpaper. A bent razer blade was used to scrape a smiling face on the wood surface to hold glue for a better glue joint.
The bridge gluing bench has a crown since soundboards have crown and bridges will be glued onto soundboard. Everything is left in the clamps over night and then ready for the next step.
When the blade is running and hits metal or when finger is within 1 inch to the running blade, the brain will be triggered to stop the blade. It sounds like a gun shot. This time the blade hit aluminum.
The new blade and brain are picked up from WoodCraft in Woburn, MA. The nut is tightened very tightly to secure the new blade.
Then install the brain below the blade. That T-handle hex wrench adjusts the height of the brain. It shall be 1/16" to 3/32" to the blade according to user's manual.
Shut every door around the blade, then install the cover, adjust height. The cover is flush to the table top of the saw. Dry run SawStop to double check before cutting anything. Off running buddy! Thank you for your company!
These batch of ribs are made of sitka spruce according to the shop owner Jude Reveley's design. The wood is milled at general thickness, width, and length.
Jude or maybe his friend designed a jig to press rib stocks in at an arch downward, then mill on table saw and planer. The wood will spring out with an arch on top. Still don't know why. But it works. The radius are different from rib to rib and is designed by him.
The top wide will be glued to soundboard. A razer is bent to scrape a smiling face on the glue surface. It allows glue to stay thus a strong glue joint. Each rib is numbered.
The ribs are made long, then cut to fit into piano.
The feathers at the two ends of each rib is pre-sawn roughly. Two locators are drilled and installed in each rib to mark location on soundboard, then replace by dowels. a locator hole for each dowel is drilled on soundboard. Before installing ribs, soundboard is cut into shape and glue surface sanded.
Ribs on! They are glued and pressed by air hoses giving enough pressure for a good glue joint. Next, the feathered ends will be sanded smooth and the surface sprayed.