Sawdust as a filler Question

[garybaldy]

I am not a Luthier so I don't have a supply of sawdust to use as a filler.
So this may seem a silly question but I want to do some sawdust/CA glue filling. I have a scrap of maple I want to use.
I intend to generate a small amount of sawdust with my belt sander. What grit sandpaper would be best to produce a suitable dust?
Thank you.

[Jimmy blue note]

Anything coarser than 600 is a material removing grit, and you'll get fine enough powder with that I believe. Finer than that gets into the polishing grits, and this would be really fine but it'll take you longer to accumulate a useable quantity.
Maybe I'm not the one to ask, cuz I have a bunch of those little marmalade bottles and I don't know what grade grit I put in there. If it's fine enough to tap off the sandpaper, it goes into that colour bottle. It's always worked fine. (ha ha)

[garybaldy]

Anything coarser than 600 is a material removing grit, and you'll get fine enough powder with that I believe. Finer than that gets into the polishing grits, and this would be really fine but it'll take you longer to accumulate a useable quantity.
Maybe I'm not the one to ask, cuz I have a bunch of those little marmalade bottles and I don't know what grade grit I put in there. If it's fine enough to tap off the sandpaper, it goes into that colour bottle. It's always worked fine. (ha ha)

Thanks very much. I'll have to get some 600 grit belts. I think I only have 80 and 60!

[AllanAllen]

What are you trying to do? 80 might be fine.

[Jimmy blue note]

Thanks very much. I'll have to get some 600 grit belts. I think I only have 80 and 60!

Try that, but with a light touch. It could work. As long as it's moving quickly and you're not bearing down with a chainsaw, you'll get useable dust.
Sorry not to be clearer, I wasn't thinking of material from a belt sander, but just creating dust from working from a sanding board or by hand.
You can get plenty fine with a belt sander, if you use a lighter touch, it takes longer but the dust will be finer.
Do experiment...and report back to us! You can become our resident gap filler/inlay go-to guy!
It's just filler powder, not cocaine. Take a line, mix up the medium and see how it works and sands back. Try different glues. Personally I've tended to avoid Cyano in situations where the touch up work is visible. It tends to sand out with a white tell tale, or at least for me.
I certainly don't have the bible of filling, no less had any hand in writing it!

[garybaldy]

What are you trying to do? 80 might be fine.

I have an old cheap double bass which I gigged with for 30 years. It has a maple fingerboard that is ebonized. In certain very localized places the ebonizing is worn through and there are some small indents caused by the strings being 'fretted' (or whatever the word is!). I don't want to get the neck done professionally and I'm not worried about the finished appearance. Just wanted to fill the indents to reduce buzzing in those few places with glue and maple dust. It looks like the finest grit ( to make the dust from my maple scrap) I can get for the belt sander is 120. Thanks
Edit. I've found 400 grit.

[AllanAllen]

I don’t have experience in this kind of repair. Your plan is logical to me, but I haven’t done something like this.

[garybaldy]

I don’t have experience in this kind of repair. Your plan is logical to me, but I haven’t done something like this.

Thanks.
My main concern is which would be the best grit sandpaper to achieve the best texture of sawdust out of the maple scrap I have.

[AllanAllen]

Well, since it's something you touch (the fretboard), it probably matters more than something you don't (the leg of an old chair).

[nevershouldhavesoldit]

I have an old cheap double bass which I gigged with for 30 years. It has a maple fingerboard that is ebonized. In certain very localized places the ebonizing is worn through and there are some small indents caused by the strings being 'fretted' (or whatever the word is!). I don't want to get the neck done professionally and I'm not worried about the finished appearance. Just wanted to fill the indents to reduce buzzing in those few places with glue and maple dust.

I don't think that approach will last very long. It won't be very resistant to abrasion and it won't be sufficiently adherent to the board. Sawdust in an adhesive binder is fine for unstressed filling of small defects with enough surface area to achieve a strong bond. But I doubt that any carrier can hold up against the constant and repetitive forces of finger and string rubbing against it. The broader and shallower the fill, the less well it will remain in place and intact when abraded.

The time honored mix for filling knicks and divots in dark woods that are not subject to destructive forces is dust in Titebond. Elmer's works better for light woods because the color of the sawdust is preserved better, but IME Elmer's doesn't seem to be as adhesive to wood as Titebond. CA is more adhesive to most materials but won't stick well if there's any oily residue on or in the wood.

I've used pure OCR (optically clear resin) without sawdust to fill small wounds on guitars for a few years and like it a lot. I just use the pure high viscosity stuff out of a syringe, although there are kits available for wood repair that work. The materials are very durable and adhesive - especially the epoxy variants. They're clear, so the underlying wood color shows through for a better looking repair than I've ever gotten with sawdust in glue. But I don't know if an OCR patch will be much more durable under strings than dust in glue. It's also harder than wood, so it would feel a bit different and could even sound a little different on a fretless board. OCRs have to be cured with UV light, and they're best used by building up thin layers. Many of the syringes come with little UV flashlights, but they're weak and take forever. I bought a good o e for about $15 that makes it go a lot faster.

The "proper" way to deal with finger board depressions is to plane the board if there's enough wood left and replace it if there's not.

[garybaldy]

Well, since it's something you touch (the fretboard), it probably matters more than something you don't (the leg of an old chair).

It needs to be pretty hard when set.

[garybaldy]

I don't think that approach will last very long. It won't be very resistant to abrasion and it won't be sufficiently adherent to the board. Sawdust in an adhesive binder is fine for unstressed filling of small defects with enough surface area to achieve a strong bond. But I doubt that any carrier can hold up against the constant and repetitive forces of finger and string rubbing against it. The broader and shallower the fill, the less well it will remain in place and intact when abraded.

The time honored mix for filling knicks and divots in dark woods that are not subject to destructive forces is dust in Titebond. Elmer's works better for light woods because the color of the sawdust is preserved better, but IME Elmer's doesn't seem to be as adhesive to wood as Titebond. CA is more adhesive to most materials but won't stick well if there's any oily residue on or in the wood.

I've used pure OCR (optically clear resin) without sawdust to fill small wounds on guitars for a few years and like it a lot. I just use the pure high viscosity stuff out of a syringe, although there are kits available for wood repair that work. The materials are very durable and adhesive - especially the epoxy variants. They're clear, so the underlying wood color shows through for a better looking repair than I've ever gotten with sawdust in glue. But I don't know if an OCR patch will be much more durable under strings than dust in glue. It's also harder than wood, so it would feel a bit different and could even sound a little different on a fretless board. OCRs have to be cured with UV light, and they're best used by building up thin layers. Many of the syringes come with little UV flashlights, but they're weak and take forever. I bought a good o e for about $15 that makes it go a lot faster.

The "proper" way to deal with finger board depressions is to plane the board if there's enough wood left and replace it if there's not.

Thanks. I would like an ebony board but I don't think the bass is worth it. I take your point about the adhesion but I think I'll try it as a quick fix and see how it goes.

[Hammertone]

Well, since it's something you touch (the fretboard), it probably matters more than something you don't (the leg of an old chair).

No frets. It's a fingerboard, not a fretboard.

[Jimmy blue note]

I have an old cheap double bass which I gigged with for 30 years. It has a maple fingerboard that is ebonized. In certain very localized places the ebonizing is worn through and there are some small indents caused by the strings being 'fretted' (or whatever the word is!). I don't want to get the neck done professionally and I'm not worried about the finished appearance. Just wanted to fill the indents to reduce buzzing in those few places with glue and maple dust. It looks like the finest grit ( to make the dust from my maple scrap) I can get for the belt sander is 120. Thanks
Edit. I've found 400 grit.

Oooo, that changes things a little. I play a fretless guitar and the issues of wear are different than on fretted instruments. I have the great fortune to be a luthier so for me, it'd be a no brainer to have my fingerboard re-planed (leveled) for a number of reasons.
It's the way I see that would provide a good playing surface for the area of play AROUND the note, and not just playing the note itself like on a guitar.
It's more permanent. And you can properly set your bridge height to a system and feel that acts as a whole, like when it was new.
When you use filler, you're working with a medium that has a different harness than the wood. On a fretted fingerboard, that's not an issue, but on a fretless fingerboard, it's essential that you have an absolutely flat surface and that means leveling the patched area so it's essentially invisible from the wood surrounding that area. Glue, any kind that will properly bind your dust, will have a hardness that is greater that the wood. That means when you go to level that area, the surrounding wood will disappear a lot faster than the patch. You wind up with essentially a "moat" around a hard island of glue amalgamate.

Knowing you're working with a fretless surface, I change my recommendations. I would try to gently dissuade you from the course of patching the fingerboard addressed on a local focus...Have it replaned. You could also work with a straight sanding stick and attempt a DIY that way but the problems you could possibly introduce are many and you have to be able to know what the string needs since you're working with a contact point as long as the string. A guitar's contact point is very localized. One fret per note. A viol family has an infinite point of contact that mirrors the absolute two dimensional line of a string.

I know you don't want to do anything fancy, but there are reasons why violin family luthiers have a different set of perspectives and skillsets than guitar luthiers. I was trained by a violin builder and a guitar luthier; different worlds. Perhaps fellow forum member RJVB, who has familiarity with violin construction and traditions, can weigh in on violin/gamba construction considerations.

Think about this before you decide which way you go.
Good luck.

[garybaldy]

Oooo, that changes things a little. I play a fretless guitar and the issues of wear are different than on fretted instruments. I have the great fortune to be a luthier so for me, it'd be a no brainer to have my fingerboard re-planed (leveled) for a number of reasons.
It's the way I see that would provide a good playing surface for the area of play AROUND the note, and not just playing the note itself like on a guitar.
It's more permanent. And you can properly set your bridge height to a system and feel that acts as a whole, like when it was new.
When you use filler, you're working with a medium that has a different harness than the wood. On a fretted fingerboard, that's not an issue, but on a fretless fingerboard, it's essential that you have an absolutely flat surface and that means leveling the patched area so it's essentially invisible from the wood surrounding that area. Glue, any kind that will properly bind your dust, will have a hardness that is greater that the wood. That means when you go to level that area, the surrounding wood will disappear a lot faster than the patch. You wind up with essentially a "moat" around a hard island of glue amalgamate.

Knowing you're working with a fretless surface, I change my recommendations. I would try to gently dissuade you from the course of patching the fingerboard addressed on a local focus...Have it replaned. You could also work with a straight sanding stick and attempt a DIY that way but the problems you could possibly introduce are many and you have to be able to know what the string needs since you're working with a contact point as long as the string. A guitar's contact point is very localized. One fret per note. A viol family has an infinite point of contact that mirrors the absolute two dimensional line of a string.

I know you don't want to do anything fancy, but there are reasons why violin family luthiers have a different set of perspectives and skillsets than guitar luthiers. I was trained by a violin builder and a guitar luthier; different worlds. Perhaps fellow forum member RJVB, who has familiarity with violin construction and traditions, can weigh in on violin/gamba construction considerations.

Think about this before you decide which way you go.
Good luck.

There is never a simple fix! May be I should get one of these instead.

[Jimmy blue note]

Well you always have options

[garybaldy]

Well you always have options

I don't normally wear a garter but I have this early 80s 'Gold on Gold'. Pic from the 80s!

[garybaldy]

I'm going for it now! Not too optimistic about the outcome but here goes. Strings and bridge removed. Bit of pressure on top to stop the post coming loose. Cleaned bare maple with acetone. Going to do a slight sand before filling. Sorry, reversed selfie images. Phone is caput.

[garybaldy]

Here's the sawdust I created and mess I've made tonight on the fingerboard. My next DB gig is 1st March - may end up having to rent a bass. At a push I'd use my Jazz Bass but I'm depping so they may not be happy.

[garybaldy]

I guess no one is particularly interest but the fb has been sanded and it's turned out great, especially as I've done nothing like it before. I've got some ebonizing solution brewing but I wanted to get the strings back on to check my work!
Next job is new pups in my Sakura es175 - a - like then I will be tackling the bent neck on my Fasan.
May have a blip in the proceedings fetching and carrying for the missus after her hip surgery (hopefully) in March.