David, I have some photos of making bridges but unfortunately they are in slide form and not yet set up to show on the internet. Some times I show these at my convention classes. I will be at the MARC convention next weekend and am doing my woodworking class. When I need a new bridge root I always make it with vertical laminations. This is the classic method and has proven to hold up over time. I have a cutoff from a bridge I made for a Beckstien a few years a go. It has ten lams each 3.25 mm thick. The height is 26.5 mm. Each strip is flat sawn so when it is glued up the top and bottom are basically radial surfaces. This will make the root and the cap have similar grain orientation that will move at the same rate with the changing RH. This way the cap glue joint will last longer. I store the hard maple for bride making in my basement. The wood moisture content for this sort on laminating should be higher than usual - about 9 - 10%. I use flat sawn wood and rip on the table saw to the height of the bridge then cut into strips a little thicker than I need. I thickness plane to final thickness. I cut all the strips from the same piece of maple. I use a clamping form made from two pieces of 3/4" birch plywood laminated together. A rectangle about 2-1/2' wide by a little longer than the bridges is glued and screwed together. The shape of the bridge is drawn through the middle and cut out. You need to make the cut with a little more curve so the right shape will result after the glue up springs back. With 3.25mm lams the spring back is small but noticeable in the base if it has a hook. Smooth one side of the form and face it with some self adhesive UHMW. The other side needs to have something that will give a little and help it conform to the bridge. I use 1/4" thick hard rubber. I epoxy this on. The two sides of the form are kept in alignment with a few battens on both sides. These should interlock so the form can't slip sideways. I use National Casein's DR powder adhesive. It's a powder you mix with water. It has a long open time and is ideal for hardwood laminations. I spread it on with a foam roller. I think you could use epoxy. Wet both sides of each strip with the glue, except the side pieces. Stack them together and slip them into the clamping form. Clamp the two sides of the form together with pipe clamps - half on top and half on the bottom. Let dry overnight, scrape excess glue off and let it cure for a month or two in a a warm dry environment. Don't forget to crown the bottom of your new bridge before gluing it on the soundboard. John Hartman RPT David Love wrote: > I need a crash course on bridge building (long bridges, bent laminated > type). Could use some suggestions on how I might go about getting > information, how to make a template, what tools I might need, materials, > etc.. Whatever can be offered would be appreciated. > > > David Love > davidlovepianos@earthlink.net > > > > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives > > -- John Hartman RPT John Hartman Pianos [link redacted at request of site owner - Jul 25, 2015] Rebuilding Steinway and Mason & Hamlin Grand Pianos Since 1979 Piano Technicians Journal Journal Illustrator/Contributing Editor [link redacted at request of site owner - Jul 25, 2015] John Hartman The Universal, How-to, Hands-on Illustrator [link redacted at request of site owner - Jul 25, 2015]
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