List folks - Del Fandrich responded directly to me regarding a recent post I made to the pianotech list. He made a point that I was not aware of regarding urea-formaldehyde adhesives. In practice I've always applied at least moderate pressure when using urea- formaldehyde, but I did suggest that isn't even necessary - apparently it is. I stand corrected, and don't want to spread any mis-information. And thanks Del for setting me straight!!! Terry Farrell Hi Terry, I'm in Korea at the moment so -- due to limitations with my normal service provider -- I can read pianotech but I can't post anything. What caught my eye was this: However, he is using urea-formaldehyde (two-part I presume), which is an adhesive that "cures" like epoxy and is an excellent gap filler. So all he really has to do is apply minimum pressure to keep the parts in alignment. Assuming he didn't crank down hard on the clamps, he is fine. Unless uf adhesives have changed quite a bit recently they tend to be rather poor gap-fillers. They will certainly fill gaps and cure but the thick glueline has considerably reduced strength. It tends to become "crumbly" over time often simply coming apart. Fillers can be added that will improve its gap-filling qualities a little bit but it will never reach the gap-filling qualities of a good epoxy. ddf -- Delwin D Fandrich Piano Design & Fabrication Consultant 620 South Tower Avenue Centralia, Washington 98531 USA Email ddfandrich at gmail.com Email del at fandrichpiano.com Tel 360 736 7563 Cell 360 388 6525 Begin forwarded message: > From: Terry Farrell <mfarrel2 at tampabay.rr.com> > Date: April 7, 2010 11:31:21 AM EDT > To: pianotech at ptg.org > Subject: Re: [pianotech] Pinblock expensive experiment > > Reasonable point. I look like his table is pretty stiff and the > clamping stock is big - but your point is well taken. It would be > especially germane if he was gluing up with Titebond or some other > sort of wood glue that requires significant pressure for a good > bond. However, he is using urea-formaldehyde (two-part I presume), > which is an adhesive that "cures" like epoxy and is an excellent gap > filler. So all he really has to do is apply minimum pressure to keep > the parts in alignment. Assuming he didn't crank down hard on the > clamps, he is fine. > > That being said, I usually vacuum bag when I cap a block. Or if I am > clamping, I will sandwich my project pinblock and cap between two > other uncut pinblocks and clamp directly like you describe. > > Terry Farrell > > On Apr 7, 2010, at 8:32 AM, jimialeggio wrote: > >> I was thinking about your original glueup problem...I would bet >> that a good part of what happened was caused by the way you clamped >> your stock. >> 1- did you clamp the multi-lam and delignit together without flat >> cauls top and bottom >> 2- looking at the clamp setup in your new glueup, the clamping >> cauls reaching across that wide presumably flat table are exerting >> unequal pressure, ie lots of pressure at the edges and considerably >> less in the center. As well, the clamps reaching over that wide >> distance will tend to deform (cup) the previously flat gluing >> table. The clamp pressure above and below should be right on the >> piece not offset. >> >> Just some thoughts..hope its helpful >> >> Jim I -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100408/8b7cdf5e/attachment.htm>
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