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Thread: Filling in the gaps

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    Default Filling in the gaps

    I'm on to the finishing touches to my first Mando build, an IV kit. Now I've got it out of the workshop and in front of a sunlit window I can see some areas between the binding and the top that have very slight gaps in them where there must have been a bit of tear out in the binding slot. How should I fill these in? I assume mixing some fine saw dust from the top or binding (I replaced the plastic binding with a strip of padauk for contrast). It's the carrier to mix it with that I'm unsure of.

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    Default Re: Filling in the gaps

    It would be better to try and match the maple. Doing what you propose would make the binding look uneven, and getting a good match that doesn’t stick out would be difficult regardless of the carrier you use for the dust. A better approach might be to use a plane to create some thin maple shavings. Then work pieces of those into the gaps with whatever glue you used for construction, trim off excess, sand flush.
    Don

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    Registered User fscotte's Avatar
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    Default Re: Filling in the gaps

    What color of stain are you going to use? If its a typical sunburst, darker along the edge, no problem using a filler for the gaps. The darker stain will cover it. If its a natural finish, I would try to cut tiny slivers of the same wood and fill the gaps. If they are miniscule then use sawdust and glue as a filler. Wood fillers are not good imo and look different under stain than the original.

    Another option is to heat the binding slightly and reset it against the ledge. But that only works if the ledge was cut evenly, otherwise you get a squirrely looking binding edge.

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    Default Re: Filling in the gaps

    Quote Originally Posted by fscotte View Post
    What color of stain are you going to use? If its a typical sunburst, darker along the edge, no problem using a filler for the gaps. The darker stain will cover it. If its a natural finish, I would try to cut tiny slivers of the same wood and fill the gaps. If they are miniscule then use sawdust and glue as a filler. Wood fillers are not good imo and look different under stain than the original.

    Another option is to heat the binding slightly and reset it against the ledge. But that only works if the ledge was cut evenly, otherwise you get a squirrely looking binding edge.
    Thanks for the info. What glue should I use? I used Titebond original for the bindings and the back but that dries a yellow colour. The gaps are a bit too random for shavings. I'll try to post a pic later. The binding is only around the spruce top. None on the bottom. And it will be a natural finish. I'm not going to chance my luck on stain just yet!

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    Default Re: Filling in the gaps


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    Default Re: Filling in the gaps

    Your links don’t work for me.

    I still think shavings is the way to go here. But, If you must use sawdust the Elmer’s or other equivalent white glue should work. Dries clear. Use a high concentration of dust and not much glue. Think of it as concrete with sawdust instead of gravel and glue acting as the cement.

    And, you’re welcome. You were addressing me too, right?
    Don

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    Default Re: Filling in the gaps

    Hi Don't. Yes it was to thank you too. Sorry about the pics. Think they may be too large. I'll try to sort that later today.

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    Mediocre but OK with that Paul Busman's Avatar
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    Default Re: Filling in the gaps

    Just a thought, but if those gaps really are "very slight" you might be better off just leaving them alone.Any glue you use could be a real pain when you try to remove the excess before finishing,leaving irregular colored patches. If you get those pictures posted, we'll be able to tell better.
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    Default Re: Filling in the gaps

    Lets see if these work. Reduced in size now.
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    You may be right Paul. Trying to fill them could be more noticeable than leaving them. This is a bit of a learning instrument as it's my first shot at building any form of musical device.

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    Default Re: Filling in the gaps

    With the dark wood binding, Im assuming you were intending a lighter or natural color. It doesnt look like thats going to be a good option and a dark burst is not going to show the binding contrast very well but seems the most logical. Slivers wont work for that and a filler of some type is best...or, rout a deeper and cleaner binding channel and and use a wider binding. If you fill, you may want to view the "mandocello build" and find the product Sunburst uses that allows color/darkness control but these are bigger gaps to fill than what he remedies. I use very thick ivoroid "mud" but for hairline gaps with ivoroid binding so, I dont have alot further advice to give for filler options. Id re-rout.

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    Default Re: Filling in the gaps

    To me it looks like you have two reasonable choices.
    1. Leave it as is and learn from the experience that you need a very clean slot for bindings if they are to look really neat.
    2. Cut the bindings out, cut the slot a little wider/deeper and cleaner, and install new bindings.

    (I would recommend for former if you just want a player and good first mandolin. If you really want it to look the best you can make it, #2 will look better than any local fill/repair.)

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    Default Re: Filling in the gaps

    Technically those are tiny "tearouts" but not what I envisioned. What are you using to cut the slot? I've used a purfling cutter in the past, and now use the 5/16" bit from StewMac. Both make very clean binding edges.

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    Default Re: Filling in the gaps

    The IV kit has a preassembled top and sides. The binding channel was already cut. Also the linings on these kits are quite thin, about the same thickness of the sides so there may not be enough "meat" to cut deeper binding slots. I have no experience of , or tools for, cutting these so could end up worse than the originals. I think the prudent action would be to leave alone and learn from it.

    You may have noticed the back isn't trimmed yet. I should have cut it closer before assembly. Another lesson I've learned. After the trouble with too thin a top which I was advised about on here (thanks to you all) I wanted to string the Mando up before putting too much more work in. I've just done that and the top has not imploded so I'm encouraged to continue! Having taken loads of time to ensure the neck was put on straight it appears to be a couple of degrees out. I'll make a jig for the next one!

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    Registered User sunburst's Avatar
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    Default Re: Filling in the gaps

    Quote Originally Posted by fretman314 View Post
    ...the linings on these kits are quite thin, about the same thickness of the sides so there may not be enough "meat" to cut deeper binding slots...
    That could be remedied by installing a purfling inside of the binding, but if you...

    ...have no experience of , or tools for, cutting these...
    ...then don't worry about that. It's more of a general statement than a suggestion.

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    Default Re: Filling in the gaps

    Yes, thanks for the pictures. Not what I envisioned either. You are right, slivers will not be a good option. Filler is your only option other than starting over. I would still match the lighter wood, not the dark binding. That would be guaranteed to look bad. Very fine spruce dust made with a file mixed with Elmer’s is what I would use.
    Don

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    Default Re: Filling in the gaps

    I'll tell you what I did that worked really well, but I don't know if you'll be able to. Is that maple? It doesn't look like it. But in any case--in my case--I was working with a red cedar top. Red cedar tends to shred. So my channels all looked like that where they ran even a few degrees against the grain.

    But like I said, red cedar tends to shred. So I ended up with a bunch of fibers. Those fibers, stuck down in the tear-out gaps, with a clear glue, did the trick. I think the glue I used was CA, but it could have been something else. In any case, the advantage of the fibers was that they were easy to manipulate, and they added an element of running parallel to the binding: the eye does not easily distinguish parallel lines, I guess. To me that was better than the risk of some sort of matrix or filler which just emphasizes the tear out and the space.

    I can't say it was perfect, but nobody's ever said, "Hey, what did you do there?" Of course that might be because the rest of it was so ugly...
    belbein

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  17. #17

    Default Re: Filling in the gaps

    Quote Originally Posted by fretman314 View Post
    The IV kit has a preassembled top and sides. The binding channel was already cut. Also the linings on these kits are quite thin, about the same thickness of the sides so there may not be enough "meat" to cut deeper binding slots. !
    First off, I'd send a note to whomever sold you the kit and complain re the quality of what you got. That's simply unacceptable.

    If you do fill, keep in mind that even clear glue inevitably makes sanding dust look darker than the original wood. Experiment a bit, and consider using a lighter colored wood than the top to make your sanding dust. I prefer clear epoxy as it doesn't shrink when it hardens.

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    Default Re: Filling in the gaps

    I've been trying out some of the spruce top sandings (I saved some just in case). And it has dried darker as you say. I have some lighter spruce which I used to thicken the top with. I'll try some sandings from that. It's a shade or two lighter than the top so it may work.

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    Default Re: Filling in the gaps

    You could also try using hide glue made from cake-making-gelatin (recipe on frets.com) - it's completely transparent unlike most wood glues, and doesn't darken the shavings quite as much.

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    Default Re: Filling in the gaps

    I will be using Tru oil as a finish. Will sawdust mixed with Tru oil work? Just a thought!

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    Default Re: Filling in the gaps

    I caution you about mixing dust with elmers: it will pretty much always be noticeable as the elmers doesn't take stain or finish well and you'll have a blotchy area. I taught guitar building at the high school I worked at, so we had ample opportunites to try fixes for gaps: here are 3 that have worked pretty well :

    1. On the spruce, commercially available pine colored woodfiller..... it sands nice, takes a stain...the water based stuff seems to work the best IMO.
    2. Make your own wood filling putty with some fine sawdust and duco cement... make it about peanut butter consistency and cram it in there.... sand flush after it has set quite a while: also better for oil/rubbed clear or mildly tinted finishes.

    3. Pack the gaps with very fine sawdust and flood it with fine CA.... the only problem with this is that CA dribbled on the padauk binding might discolor it.

    In every example, it's best to practice on scrap first....

  22. #22
    Registered User Tavy's Avatar
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    Default Re: Filling in the gaps

    Quote Originally Posted by fretman314 View Post
    I will be using Tru oil as a finish. Will sawdust mixed with Tru oil work? Just a thought!
    I would stay away from that: if the TruOil/wood packing is deep it'll take forever to set hard.

    BTW, any glue/binder that soaks into the shavings will cause them to go much darker - and that includes things like thin CA (which would otherwise be ideal). It is I'm afraid, a tough nut to crack!

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