> From: "David Nereson" <da88ve at gmail.com> > Date: January 26, 2010 9:08:39 PM EST > > I rebushed a set of keys using the nylon Spurlock cauls. The pins were .146" so I used that size caul. When done, the keys still wobbled laterally (balance rail). This has happened a couple times now. I had done no easing or ironing after removing the cauls. Should I have used a smaller caul (even tho' the size I used is meant for that size pin) or thicker bushing cloth? Or both? When I initially determined what thickness cloth to use, by laying the trial cloth across the mortise and pushing a key pin into the hole, thick seemed way too tight. Medium was just right (could be pushed in, but holding the key upside down, the pin would not fall out -- this is according to the Spurlock directions). > Once I steamed 'em all back out and rebushed with thicker cloth, but using the same cauls, and they still came out too loose (too much lateral play). So do you use a smaller caul than the one intended for a given size pin? > --David Nereson, RPT Hi David, I am not sure what is going wrong for you. You description of the process for choosing cloth thickness sounds correct, and, no, you shouldn't have to change caul size. Here are a few questions, or things to try: 1) Measure the cauls. For .146 pins, my type I cauls (with one black band across the top) mic out at about .184, and my type II cauls are .148 (with two black bands across the top). Bill Spurlock typically does excellent machining, but the first thing I would check is the caul sizes, just in case. 2) Re-measure the pins after they have been polished. I have come across a few sets that looked like .146, and measured close to that with a (somewhat inaccurate) caliper, but were really about .142 when polished and measured with an accurate micrometer. 3) Check the depth of cloth insertion. If you use the Spurlock method and insert the cloth too far, you will end up with too much friction and sticking keys. If you insert the cloth too shallowly, you will end up with too little friction. It is critical that your cloth insertions be at the right depth, and that can be challenging to get the hang of with this method (it's not enough of a problem to make me go back to the Bushmaster system, however). 4) What kind of glue are you using? Medium thick hot hide glue (following prior hide glue sizing) acts as a "filler" in some cases, and can fill a little space in a slightly worn mortise, especially if the wood is splintering. If you use a different or thinner glue, you will not gain this benefit. 5) I will chime in to second advice others have given: get more cloth sizes, and use mortise sizing cauls. Good luck with it, Joe DeFazio Pittsburgh -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100127/59fb49ef/attachment-0001.htm>
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