---------------------- multipart/alternative attachment While at Yamaha an amazing new method for repairing cracked piano was shared by another member of the group. This is a completely new technique and is unlike anything previously discussed. This group member also brought a video tape for show and tell which put everyone in awe. Even LeRoy was dumbfounded and is now wanting more information. This is no joke folks, read on... This crack repair method was developed originally for repairing cracked cast iron engine blocks and other heavy machinery. It involves no welding whatsoever. Instead a series of very specially designed screws are inserted into the crack which quite literally pull the crack together stronger than it was before. When the repair is complete it is almost invisable. This may sound to good to be true but the tape demonstrates this clearly. Two flat pieces of cast iron were fastened together in a butt joint by a single one of these screws, and was then hooked on each end with a heavy chain. The chain was then connected to a wench which lifted a 350 pound engine block. The bond held perfectly. A complete series of pins overlapping in a crack seals the crack permanently and stronger than it was originally. On bench tests these repairs were shown to be completely air tight at 80 PSI. Ok, so here's how it works. The screws are designed to dig in to the cast iron. They must go into a pre-drilled hole using a special bit. The holes are also taped. The secrete is in the screw threads which are cupped sharply upward. The top half of the screw has a countersunk collar which pulls tightly into the hole in the opposing direction of the cupped threads. The screw is driven into the cast iron using an air drill until the torque breaks of the head. The result is that the cast iron is clamped tightly together *internally*. A series of these screws are installed to follow the crack side by side. Then an overlapping series of screws are inserted in a second pass. The remains of the torqued-off heads are ground away smooth. No welding, no mess. This type of repair can even be made inside the piano without plate removal. There are several types of these special screws which can be used on various types of cracks, even on angles or in corners. They are also available in various lengths. The video presentation was extremely convincing and had us talking about it for the remainder of the week. This group member's local chapter recently decided to try this repair as a joint project. The inventor of this technique was personally present and assisted in explaining and then demonstrated the repair. This proceedure is brand new and this was the first such repair made on a piano. I think we can all pretty much expect to hear a lot about this very soon. This repair system is called the "CastMaster" by a company called Lock-N-Stitch. They do have a web page. Check it out and be amazed. Lock-N-Stitch Follow the link to "Information about Cast Master". After you've read the text and looked at the pics, go to the link that demonstrates the complete repair. Enjoy! Rob Goodale, RPT ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/d6/c1/52/c3/attachment.htm ---------------------- multipart/alternative attachment--
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