SwedishLuthier Posted June 7, 2007 Report Share Posted June 7, 2007 (edited) Up to now I have always hand buffed my guitars with this. Now I decided to step things up a little and invested in a bunch of these. First test object was an acoustic finished with LMII KTM-9 following this instruction. I prepared the wheels following the instructions from Frank Fords page, raking the wheels, even things out using scissors, loading the wheel, more raking and scissors and so on until I figured the result was OK. My buffing arbor is a bench grinder, 750W, with a frequency converter to get the speed down to around 1000 rpm. I have not measured the speed but I run the motor at around 20 Hz, so it *should* be OK. Now to my problem. The over all luster is very good but in some parts there is some pitting appearing following the grain pattern. Or more exact the part of the back that had a thicker covering (finish + grain filling). My first thought is that I may have been using to hard pressure, so I used a lot less pressure on the front. The result is better but still some problems of the same type. In the cut away area I used too much pressure and the finish got a nice orange peel effect, so now I know how too much pressure looks. I now suspect that I have used too little buffing compound. My real question is: How can you tell when you have the right amount of buffing compound?â€. I know that a picture of how the wheels and the pitting look is of great help. I will try to get that tonight (at work right now, goofing). Another thing: How do you guys get into the cutaway area with the buffing wheels? Edited June 9, 2007 by SwedishLuthier Quote Link to comment Share on other sites More sharing options...
SwedishLuthier Posted June 9, 2007 Author Report Share Posted June 9, 2007 (edited) Unfortunately it is impossible to get a good picture of the pittings. But this is how much buffing compound I'm using. Is it to little? To much? Edited June 9, 2007 by SwedishLuthier Quote Link to comment Share on other sites More sharing options...
Daniel Sorbera Posted June 9, 2007 Report Share Posted June 9, 2007 That picture looks a whole lot darker than mine Mine is light creamy color (the color of the stick compound) You are using this right? Quote Link to comment Share on other sites More sharing options...
SwedishLuthier Posted June 9, 2007 Author Report Share Posted June 9, 2007 Jup, thats the wheel with the coarse compound. I'm using coarse and fine. For starters I flatten the finish with 600 grit papaer and then proceeded as in the instructions. The fine is about the same color as the wheel so I figured it would't really show up any good in the pictures... Quote Link to comment Share on other sites More sharing options...
Daniel Sorbera Posted June 9, 2007 Report Share Posted June 9, 2007 Jup, thats the wheel with the coarse compound. I'm using coarse and fine. For starters I flatten the finish with 600 grit papaer and then proceeded as in the instructions. The fine is about the same color as the wheel so I figured it would't really show up any good in the pictures... Oh ok thats the difference. I sand up to 2000 and start with the fine than go to extra fine. I thought you might have been burning it somehow, but it doesn't look like thats the case. Quote Link to comment Share on other sites More sharing options...
SwedishLuthier Posted June 10, 2007 Author Report Share Posted June 10, 2007 So does this look like about the right amounth of buffing compound? I keep asking because the Stewmac instructions says that too little compound can cause heat build-up that drag the finish of the instrument. Quote Link to comment Share on other sites More sharing options...
Hydrogeoman Posted June 12, 2007 Report Share Posted June 12, 2007 So does this look like about the right amounth of buffing compound? I keep asking because the Stewmac instructions says that too little compound can cause heat build-up that drag the finish of the instrument. Good question that I have not really seen a definative answer for. FWIW as I am pretty new to the buffing deal, I use the Stewmac arbor buffer (runs at 860 rpm) with the Menzerna fine and extra fine compounds. For me, I have found the best results (on nitro lacquer finishes) lightly loading the buff by holding the compound bar on the wheel for no more than 3 seconds with light pressure. Loading more than this usually causes the compound to buildup on the guitar surface which then has to be wiped off with a damp cotton cloth. I usually load the buff with a single compound no more than 3 or 4 times for a complete guitar. While buffing, I apply extremely light pressure to the guitar. At 860 rpm you really won't have any burn problems by applying light pressure and by keeping the workpiece constantly moving. As for reaching into the cutouts, I get in as close as I can by angling the guitar without hitting the steel washers and arbor nuts, then finish up by hand. I learned the hard way not to try an get the guitar too close to the spinning metal parts Also, I both the fine and extra fine compounds do very little to nothing to remove scratches. That being said, I have been wet sanding with micromesh cloth backed "sand paper" starting with 1800, 3200, 4000, 6000, and 8000. I am thinking of trying some additional buffs with coarser compound to see if I can eliminate some of the labor involved going through all the various grits of micromesh. Good luck! - gpp Quote Link to comment Share on other sites More sharing options...
SwedishLuthier Posted June 12, 2007 Author Report Share Posted June 12, 2007 The opinion over at the MIMF forum was that I should use more compound, up to 4 re-loads for a front or back. Also th slow down the speed fom 9-1000 (I will try to measure it later on) to no more then 800 rpm. I get rid of the scratches from the 600 grid ppaer with the coarse compound. I need to follow the fine with some swirl remover so an extra set of buffs with extra fine wouldn't hurt. Quote Link to comment Share on other sites More sharing options...
erikbojerik Posted June 12, 2007 Report Share Posted June 12, 2007 Peter, I would (and do) use Abralon pads 600-1000-1500-2000 on a random orbital sander (by hand in the cutaways), then buff fine & extra-fine. Quote Link to comment Share on other sites More sharing options...
brewu22 Posted June 14, 2007 Report Share Posted June 14, 2007 Some pics of the pitting would help a lot. I have the same setup, and have had no problems. I have the medium and fine compounds. I wet sand to 1200, then buff. Have you buffed through the finish, and the grain filler? just a thought. Quote Link to comment Share on other sites More sharing options...
SwedishLuthier Posted June 14, 2007 Author Report Share Posted June 14, 2007 Erik: I have tried to find finer grade pads for my orbital sander but yet without success. The local suppliers only carry up to 240 grit. The Stewmac instructions say sand to 600. Then start with coarse. As the buffing took only a few minutes I will rather get a third wheel and load that with extra fine compound. Brewu22: I have tried to take pictures but the pitting doesn’t show up at all. I have tried different lights, angles etc, but without luck. I haven’t sanded through the finish. There is still finish “at the bottom” of the pit. The pittings are following the grain pattern of the mahogany, maybe up to 1 mm (about 0.04”) wide and 20-25 mm (up to 1”) long. The depths of them are very shallow but deep enough to show up in direct light. They are too deep to be able to sand away and re-buff so I’ll have to re-spray the back. One suggestion over at MIMF was that excessive heat from slightly to high speed and to little compound melted the grain filler. That is possible. I tried the LMII grain filler for this guitar and I was not very satisfied with that. It has the consistency of chocolate mouse and might collapse from the heat under the finish while the finish stays intact. Just a thought thou. Quote Link to comment Share on other sites More sharing options...
PaintIt Posted June 14, 2007 Report Share Posted June 14, 2007 I generally sand with 1500, 2000, 3mtrizac3000 and then regular 3 stages of 3M perfectit compounds. the 3000 makes the surface have a satin shine and make the buffing realy quick. If you are using uro clear I would say the pitting is solvent pop that has been sanded open. Not familar with laquer clears and if this happends or not. Caused buy not waiting long enough for coats to flash off and little bubles form under the surface and when sanded look like little pits. Quote Link to comment Share on other sites More sharing options...
bentwood999 Posted June 17, 2007 Report Share Posted June 17, 2007 Load that wheel up with compound (dont forget to wear a mask) dont be afraid i sand it up to 8000 then start it comes out like a mirror at 1000 rpm Quote Link to comment Share on other sites More sharing options...
Daniel Sorbera Posted June 17, 2007 Report Share Posted June 17, 2007 I'm thinking that your problem may not be related to your buffing. Are you sure the finish is fully cured and are you sure the grain filler is fully cured before you start finishing? Quote Link to comment Share on other sites More sharing options...
Bertbart Posted June 17, 2007 Report Share Posted June 17, 2007 I'm thinking that your problem may not be related to your buffing. Are you sure the finish is fully cured and are you sure the grain filler is fully cured before you start finishing? I agree with you Godin. It sounds like the finish wasn't cured. I sand to 1200 and use the Mezerna fine and then extra fine. I hand rub the cutaways with either Meguire's or 3M finesse II. I'd stay away from any compound heavier than fine. I wait two weeks after sanding with 800 before going over it with 1200 and then buffing. I feel like leaving it with the finish opened by the 800 lets it vent out more thoroughly. I shoot lacquer always. Quote Link to comment Share on other sites More sharing options...
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