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BEST WOOD FILLER?

Discussion in 'Luthier's Corner' started by Gilmourisgod, Apr 29, 2015.


  1. Gilmourisgod

    Gilmourisgod

    Jun 23, 2014
    Cape Cod MA
    So I have a little tearout in hard rock maple body wings:
    IMG_2469_zpsljdsw5dp.
    IMG_2470_zpstcmhegrd.

    What's the consensus out there on best wood fillers? I want something that will dry about as hard as the maple, but not a lot harder, so it sands evenly with the wood. A few fillers I've considered:

    Minwax High Performance Wood Filler - Sounds fancy, but it's just bondo with some fine wood dust in it. The downside of any bondo product is getting the mix right, they usually only give mix info for the whole can and you end up guessing.

    West System Epoxy with maple sanding dust mixed in. I have the small containers with metering pumps, so I end up using at least one pump each regardless of how small the project is, to get it right.

    West System Epoxy with 404 High Density, 407 Low Density, or 410 Microlight Filler.
    I have some of the 404 and 410 fillers, tried the 410 to fill some nicks and low spots on a template I made, and it seemed to work pretty well on MDF, but I'm wondering if the microlight fairing is too soft for rock maple filler.
    IMG_2460_zpstadlmy6h.

    Advice greatly appreciated!
     
    Last edited: Apr 29, 2015
    blindrabbit likes this.
  2. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    I've been doing spot fills like that for years using plain West Systems 105/205 epoxy with no added fillers. It's the best repair method I know of. It files and sands nicely, level with the wood, and doesn't shrink or move under the paint. Dab the epoxy in the hole and cover it with a piece of wide masking tape to hold it in there.

    I haven't played much with the various fillers, and I haven't liked the results so far. They make the patch too soft and porous. I like the epoxy by itself.
     
    SirMjac28 likes this.
  3. Hopkins

    Hopkins Supporting Member Commercial User

    Nov 17, 2010
    Houston Tx
    Owner/Builder @Hopkins Guitars
    Those tear outs are small enough that they will sand out without any noticeable change in the shape of the body. I wouldn't use any filler at all, just some 80 grit on a sanding block.
     
    Dadagoboi and GMC like this.
  4. Gilmourisgod

    Gilmourisgod

    Jun 23, 2014
    Cape Cod MA
    They are deeper than they look, the one on the curved body edge is a fat 1/16th, and the one on the horn edge would really change the shape to sand out. I'm surprised at the no filler approach, I would have thought straight West epoxy was too thin on it's own. Does the masking tape come off once it's epoxied, or does that effectively get sanded off also? I'll give it a try on some scrap and see how it goes. I have some surface tearout on short grain sections too, not really wood loss, more like crushed fibers or "road rash" where it turns grain:
    IMG_2471_zpsq267azgs.
     
  5. Hopkins

    Hopkins Supporting Member Commercial User

    Nov 17, 2010
    Houston Tx
    Owner/Builder @Hopkins Guitars
    It wont change the shape as much as you think it will, as long as you blend it well with the body lines. The horn will not require much wood to be removed at all, if you use a cylindrical sanding block and work it out from the cut away section keeping that edge sharp, I would bet my last dollar you would never even notice a difference. As far as the edge, if its deeper than it looks in the picture, drop filling it with CA glue and sanding it flush will work fine.
     
    Dadagoboi and Manton Customs like this.
  6. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    The masking tape usually just pulls right off of the epoxy. If a few scraps stick on, they will easily come off while filing and sanding the epoxy to level. The tape acts like a temporary mold, holding the epoxy to the shape, slightly above the surface. It cuts down on the amount of filing and sanding. I level the patch down with a file, then smooth it with sandpaper, usually 180.

    On all of my bodies made from poplar and ash, I use the plain West Systems as the grain filler. I dab it on with a wool dauber (from Tandy Leather), let it cure, and sand it back level with the surface. It does the rough grain filling, as well as filling any chips and tearout. I've been using the West Systems as a grain filler for about 20 years, and it's been absolutely solid and stable.
     
    SirMjac28 likes this.
  7. Gilmourisgod

    Gilmourisgod

    Jun 23, 2014
    Cape Cod MA
    Thanks Bruce and Hopkins, sage advice per usual, great to have professionals on TB to help out the noobs! Got some 150 and 100 grit 1" x 2" sanding sleeves for my Robosander on the way, epoxy filer first and then sand to template prior to starting hand sanding.
     
  8. Manton Customs

    Manton Customs UK Luthier

    Jan 31, 2014
    Shropshire, UK
    Luthier, Manton Customs
    I agree 100% with Hopkins. All bodies can vary a little even on mass produced instruments due to the sanding, you'll see lots of mentions of this when it comes to people looking for an accurate blueprint of a 50s Les Paul. Lots of different originals were traced and none of them matched! There turned out to be quite a bit of variation in just the body outline alone due to the sanding which took place at the factory. I imagine things have come a long a fair bit since those days, but mistakes still happen at the factory which have to be sanded out and sanding will always be a necessary part of the process too. Another example of this is Fender neck pockets, sanding at the factory is the reason they can be all over the place ranging from gappy to too tight.

    So don't sweat it :)! Also those baring marks may steam out with a soldering iron, though there isn't a lot of point seeing as you have to do a lot of sanding anyway.
     
    McFarlin likes this.
  9. What is the "plain" West System (which formula)? Is it clear? I've got bad tearout on a top piece that needs filled. I also need to fill in a carbon fiber rod slot that's not as tight as should be.
     
  10. Gilmourisgod

    Gilmourisgod

    Jun 23, 2014
    Cape Cod MA
    I use the 105 resin and 205 hardener, cause that's what I have for boat repairs. The hardener seems to impart a slight pinkish tinge while mixing it, but it dries more yellowish, definitely not water-clear. That works fine for reddish tinged wood like mahogany. It doesn't matter in the case of painted finishes I suppose. I used the 105/205 mix to glue in my carbon fiber rods, seemed to work fine. I've read about people using this for a sealer prior to paint, which seems odd. Doesn't epoxy produce a waxy "blush" on the surface when it cures? Can laquer-based primer go right over epoxy? I bought a kit like this one, which has resin, hardener, and metering pumps, got mine from West Marine.
    WEST System Epoxy Kit
     
  11. fjadams

    fjadams

    Jun 7, 2011
    Danbury, CT
    I use the MinWax High Performance Wood Filler, it's a 2 part filler.
    My luthier uses Feather-Rite body filler.
     
  12. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    What I mean by the "plain" West Systems formula is the 105 resin and either the 205 (fast) or 206 (slow) hardener, with no other added fillers. You generally don't want to use the fast 105/205 mix anywhere that the epoxy will be thicker than about 1/4". I'll use the fast 105/205 mix for some spot fills, but I usually use the slow 105/206 mix for most grain filling. Either mix will have some amber tint, but it will be less with the slow mix. If the hardener is fairly fresh, the epoxy will dry close to clear.
     
  13. Related to your tearout Gil, I've got this to deal with:
    IMG_20150429_201729910. IMG_20150429_201741815_HDR.
    I planned on using Tru-Oil. How do I fix this?
     
  14. Means2nEnd

    Means2nEnd Supporting Member

  15. OK but what I want to know is............what is the Best Wood Filler for Metal?.......
     
  16. Gilmourisgod

    Gilmourisgod

    Jun 23, 2014
    Cape Cod MA
    Robert Canfield likes this.
  17. Gilmourisgod

    Gilmourisgod

    Jun 23, 2014
    Cape Cod MA
    I'm thinking sanding dust from the wood you want to match mixed into putty with epoxy, but it never looks quite the same as the surrounding wood. The Stewmac laquer stick idea is interesting too. Never tried it, but a lot of furniture repair guys use it for nearly invisible repairs.
     
    Last edited: Apr 30, 2015
  18. Means2nEnd

    Means2nEnd Supporting Member

    I think in the video above that's embedded in the Stew Mac site that guy is trying to get it to fill the void or dent/scratch and at the same time melt into the finish as a "seamless repair on a finished product"

    in the LMI Robert O'Brien demo he was filling the the voids where the fret ends are at the edge of the fretboard. I think this is a much easier job to accomplish as you just need to fill and then you can sand then finish not doing it after the fact. I think we can agree matching exactly a non painted figured piece of wood with a clear or slightly stained finish is almost impossible to match perfectly. I think material wise the epoxy would be the best and easiest to work with but to match or fill a void it needs to be opaque and the lacquer stick would still be easy enough to melt in a fill and the color options are pretty varied and could get pretty dang close. I don't think filling a chunk is ever an easy task whatever the method. I would rather sand it out if possible if the universe was kind enough to have it happen on a round over but on a flat plane it presents a whole new set of curse words to be screamed through my 3M face mask.
     
  19. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    Yes, the lacquer stick products are for hiding small chips in wood that already has a finish on it. It's a mix of lacquer and wax and a dye. A glorified version of shoe polish. Fine for touching up a finished product, but you do not want to use it to fill chipped wood that hasn't been finished yet. The finish won't stick to it, and it will sink down over time.
     
  20. fjadams

    fjadams

    Jun 7, 2011
    Danbury, CT
    Bondo. 50,000 body shops can't be wrong.
     

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