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PostPosted: Fri Jun 14, 2019 6:04 pm 
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Koa
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So do I need to respray this w a few coats???
Looks like I got a sand through that I didn’t notice until I buffed it
Still learning
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PostPosted: Fri Jun 14, 2019 6:14 pm 
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Brazilian Rosewood
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Fraid so...



These users thanked the author meddlingfool for the post: SnowManSnow (Fri Jun 14, 2019 6:34 pm)
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PostPosted: Fri Jun 14, 2019 6:35 pm 
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Koa
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All good. Just another few weeks to cure . No hurry :)
Peace
Thanks Ed


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PostPosted: Fri Jun 14, 2019 6:55 pm 
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Koa
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The good part is the rest turned out like this:)
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Just have to have things done by Christmas is all so no rush.


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PostPosted: Fri Jun 14, 2019 7:11 pm 
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Snow

Looks like you may have unintentionally rounded over the edges a little. Be sure to use a sanding block of of some sort and don't let it go out over the edges when sanding. Nice finish on the body.

Ed



These users thanked the author Ruby50 for the post: SnowManSnow (Fri Jun 14, 2019 7:14 pm)
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PostPosted: Fri Jun 14, 2019 7:14 pm 
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Koa
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Ruby50 wrote:
Snow

Looks like you may have unintentionally rounded over the edges a little. Be sure to use a sanding block of of some sort and don't let it go out over the edges when sanding. Nice finish on the body.

Ed

You’re right.


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PostPosted: Fri Jun 14, 2019 10:53 pm 
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I've sanded through on headstocks more than once. Hate it when that happens. One tip I'm pretty sure I picked up from this forum is instead of wrapping sandpaper around a sanding block, cut a piece of sandpaper the size of the sanding face of the block and double stick tape it to the block. The reason is that wrapping the sandpaper around the edge of the block causes the sandpaper to curve out slightly from the block where it wraps around the edge. It's not much but it's enough to cause more aggressive sanding at the edge of the block which is a problem as the edge of the block approaches the edge or corners of a small surface like the headstock. With the sandpaper double stick taped to the face of the block and not wrapping over the edges of the block, the sandpaper is flat all the way across the surface and you are less likely to sand through. Once I started doing that, the sand throughs stopped happening. This assumes that the wood surface is actually flat all the way across.

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These users thanked the author J De Rocher for the post: SnowManSnow (Fri Jun 14, 2019 11:33 pm)
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PostPosted: Sat Jun 15, 2019 4:48 am 
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Koa
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My natural tendency is to place far too much pressure on the edges, so early on in my training as a professional sander of wood and finishes (aka, luthier), I got three pieces of guidance:

- Stay off the edges

- No really - stay off the edges!

- You know, that wouldn't happen if you'd stay off the edges

But seriously, the techniques I learned focused on minimizing edge sand through and buffer burn through by doing the following:

- Properly prepare the surface before filling by rounding the arrises of the peghead sightly - this allows both a more uniform coating thickness on the edges (most coatings behave differently on edges than on flat surfaces, with lacquer flowing away from sharp edges, resulting in thinner film thickness there), and that slight radius spreads any applied sanding block pressure over a larger area.

- Unless a very conscious effort is used to reduce pressure on the block when operating over an edge, sanding pressure on the surface goes up as the area of the block in contact with the surface is reduced. Use a circular or oval sanding pattern on film-forming finishes like lacquer or waterbased polyurethanes or acrylics...besides eliminating the sort of deep, parallel scratches that are difficult to deal with when moving to the next finer grit, this sanding pattern keeps the pressure on the block more uniform and allows more of the block to stay registered on the surface (thus, avoiding excessive thinning of the finish film at the edges).

- Keep the pressure on the block inside the edge - this keeps the block flat and registered on the surface, versus following the edge and applying excess sanding pressure at the arrises.

- Avoid the issue noted above by Mr. De Rocher by using sanding blocks with a thick applied cork face and edges rounded or at the very least treated with a deep chamfer, then eased with the sander. This is more easily done with a cork face than wood, and the cork surface is more easily flattened after the first wet use on lacquer or oil varnish. This also encourages the sort of frequent paper changes needed when dry sanding water-based finishes and avoids the need to deal with double-stick tape or PSA when changing worn paper for fresh.

Attachment:
SandingBlocks.jpg


- Wet/dry papers to be used wet on lacquer or varnish should be soaked at least overnight - it softens the paper, allowing it to better conform to the block, as well as making the paper much easier to clear. We have 15-20 pieces each of 400, 800, and 1200 3M Imperial that live in plastic tubs ready for use, with a drop or two of Dawn detergent to discourage slime formation.

- Buff off the edge, keeping any pressure applied inside the edge, just as sanding pressure applied is kept inside the edges


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These users thanked the author Woodie G for the post (total 2): TimAllen (Tue Jun 18, 2019 1:10 am) • SnowManSnow (Sat Jun 15, 2019 8:46 am)
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PostPosted: Sat Jun 15, 2019 8:46 am 
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Koa
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Scuffing and respraying this morning


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PostPosted: Sun Jun 16, 2019 3:25 pm 
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Koa
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Woodie G wrote:
- Keep the pressure on the block inside the edge - this keeps the block flat and registered on the surface, versus following the edge and applying excess sanding pressure at the arrises.


What are arrises?


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PostPosted: Sun Jun 16, 2019 5:57 pm 
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Koa
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The sharp edge or salient angle formed by the meeting of two surfaces.

_________________
We have become a civilization that elevates idiots, prostitutes, and clowns. Am I still to defend it? Yes, for its principles. Yes, for what it was. Yes, for what it still may be.

-Mark Helprin, The Oceans and the Stars: A Sea Story, A War Story, A Love Story (A Novel)



These users thanked the author Woodie G for the post: Conor_Searl (Sun Jun 16, 2019 5:58 pm)
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PostPosted: Sun Jun 16, 2019 6:44 pm 
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A table top with a square edge has an arris at the top/edge corner and at the bottom/edge corner. Your chisels have arrises (arissi?) at the sides where the edges meet the face and the back.

Ed



These users thanked the author Ruby50 for the post: Conor_Searl (Mon Jun 17, 2019 12:03 am)
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PostPosted: Mon Jun 17, 2019 12:03 am 
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Oh boy, a new word! Can hardly wait to use it in a sentence. I'll have to be careful not to mix it up with arse.

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