> Do you mix up a new batch of resin and hardener for the filler, or > do you add it to the same batch that you just used for the wetting > coat? Doesn't matter. Just depends on how big an area you are doing and what hardener you are using. The only rule is to apply the thickened epoxy before the unthickened wetting-out coat has fully cured. If I'm doing a small area (like maybe one of your treble pieces), maybe I'd mix up - oh gosh, a hundred grams or so (I'm just guessing here), paint the thin epoxy onto the edges of the insert and the cut-out, then throw a bunch of #404 filler in there, mix it up and apply to (in this case) both surfaces and push the insert into position. But I'm using the slow or extra slow setting hardener, and it is winter and my shop is cool. If it were summer, I might mix up separate batches of epoxy for applying the first thin coat and a second batch of thickened stuff - just depends on the working time you have with the ambient conditions. > The part about the pin block jacks is a little confusing to me as > well. Do you just use them as stands? Or are you actually pushing > against something? If the latter, what is on the top side that you > are pushing against? Without the pinblock jacks, how are you going to hold the inserts in position so that the bottom of the insert is level with the bottom of the pinblock and the top of the insert is level with the top of the pinblock? Simply position the pinblock jack under the section of pinblock you are bonding - add a piece of plywood covered with plastic if the jack doesn't cover the entire cut-out area. The pinblock jack I have is from Pianotek and it is maybe 8" x 4" or so - it has two machine screws to raise and lower a thick section on pinblock material. The jack, with a piece of plywood and plastic atop it is more than a stand, it defines the base of the pinblock. It is pushing against the bottom of the pinblock. Again, put the pinblock jack on the keybed, slide it under the pinblock, put a piece of plywood on top of the jack large enough to cover the cut-out and put a piece of plastic on top of the plywood. Raise the jack so that the plastic--covered piece of plywood is snugly against the bottom of the pinblock. When that is done, your cut-out now has a bottom - you could fill the cut-out with water and have a very small swimming pool - if you were a very small person..... Does that make sense? Now your cut-out has sides (like it always did), but now it has a bottom (the top of the plastic/plywood topped jack). Now when you place your insert in the cut-out, it won't fall through - because the jack assembly is there. I hope this clears things up - I wish I had a picture, but I don't think that I do. Sorry. I think this is something that once you understand what I am talking about it is very basic and obvious. But before that I suppose it can be confusing. Let me know if I am still not clear. Terry Farrell On Apr 1, 2010, at 7:43 PM, Dean May wrote: > Thanks, Terry, this is very helpful. I was a little concerned about > how much nominal gap to build into the system to provide room for > the glue, thinking maybe 1/32 per side, so hearing that up to 1/4” > is okay gives me some relief. > > The adding filler part from West System is a little confusing to me: > > Apply thickened epoxy to one bonding surface. Modify the resin/ > hardener mixture by stirring in the appropriate filler until it > becomes thick enough to bridge any gaps between the mating surfaces > and to prevent "resin-starved" joints. Apply enough of the mixture > to one of the surfaces, so that a small amount will squeeze out when > the surfaces are joined together with a force equivalent to a firm > hand grip (Figure 10). > > Do you mix up a new batch of resin and hardener for the filler, or > do you add it to the same batch that you just used for the wetting > coat? > > The part about the pin block jacks is a little confusing to me as > well. Do you just use them as stands? Or are you actually pushing > against something? If the latter, what is on the top side that you > are pushing against? > > Dean > > Dean W May (812) 235-5272 > > PianoRebuilders.com (888) DEAN-MAY > > Terre Haute IN 47802 > > From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] > On Behalf Of Terry Farrell > Sent: Tuesday, March 30, 2010 5:26 PM > To: pianotech at ptg.org > Subject: Re: [pianotech] pin block inserts > > Hi Dean. Cut the inserts out to fit easily into the cut-outs - don't > worry about a perfect fit - you'll be using a good gap-filling high- > strength epoxy anyway. Even if there are quarter-inch gaps here and > there, no big deal. I'm not sure I understand the method of cutting > you describe below, but it appears you routed out the pinblock cut- > outs. Epoxy makes a mechanical bond with wood, so any roughening of > the surface you can will be good. If you are applying thin epoxy > resin to the wood, it would probably soak in enough that roughening > wouldn't matter - but since we don't really know how far it will > soak in, absolutely, IMHO, it would be a good idea to roughen the > wood bonding surface. I cut my pinblock cut-outs with a saws-all saw > - so it left me a nice rough surface anyway. > > Because of the stresses that will be applied to your pinblock, and > the relatively small bonding surface area you will have, you really > want to make sure you make the best epoxy bond possible. I used the > West System Two-Step Bonding Method, which I strongly suggest is the > best way to do this job. http://www.westsystem.com/ss/bonding-gluing-clamping/ > > Another good way to work thin epoxy into a surface that doesn't soak > up much this epoxy (this is how West System recommends bonding > metal), is described about half way down this page - point #3 http://www.westsystem.com/ss/bonding-hardware/ > Basically, they recommend sanding (with very coarse paper) the > thin epoxy into any non-porous surface to be bonded. I've even had > very good results using this method when I wanted to bond a plastic > pipe to something - and we all know that epoxy won't bond to plastic > - or at least we thought it wouldn't! > > After wetting out the two surfaces, I highly recommend using West > System #404 High Density filler - it is their highest strength filler. > > The method I used to align the inserts to the cut-outs was to first, > make sure my inserts are the same thickness as the block. Then I > used my pinblock jack (the thing you support the pinblock with when > driving tuning pins into the block), with a piece of flat plywood > (larger than your cut-out) on top of it and a piece of plastic on > top of that. Put it under the cut-out, snug it up to the bottom of > the block, and now you have an automatic insert leveling system and > also something to prevent any low-viscosity epoxy from oozing out > from the bonding area. > > Hope this helps. The last piano I used this method on I tune every > few months - and it holds it's tunings wonderfully. > > Terry Farrell > > On Mar 30, 2010, at 10:16 AM, Dean May wrote: > > > This is the pin block from the piano tear down I just posted > pictures of. It is a rather complex shape with several different > levels- beyond my meager woodworking skills to duplicate. I could > have used plugs but borrowing from Terry Farrell, I decided to > router out the pin fields. I drew boxes around 3 pin field areas- > the two in the treble happened to come out so I could make them the > same size. I then transferred the dimensions of those boxes to a > piece of OSB board. I then drew a box 2.75” bigger all the way > around (6” router base, 1/2" cutting bit) and cut out the big box to > make my pattern. Since I was able to make the two treble cutouts the > same, I only had to make two patterns. Today I am going to a big > woodworking shop owned by a friend and I intend to cut out the > inserts on a good band saw. > > I plan on epoxying the inserts into place. I was wondering if > scoring the surfaces with a coarse rasp file, instead of leaving > them smooth, might give the epoxy better surfaces to bond. > > Dean W May (812) 235-5272 > PianoRebuilders.com (888) DEAN-MAY > > Terre Haute IN 47802 > > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100331/cd7c27af/attachment-0001.htm>
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