Wednesday, September 19, 2012

The Guitar Saga, Post III: also known as (updated)

'Well, that answers that.'
'That' being the use of the scraper. In about an hour I was able to remove almost all traces of the original finish from the sides, and then did a bit on the front. Except for some separation around the bottom curve, the finish on the front is in a lot better shape than the sides & back; and, except for those areas, this finish will not come off the way the rest did. So, a lot of sanding.

The scraper did save me a huge amount of time on the back & sides, so very happy I tried it. I started sanding on the front, will see if can get most of the finish off. It'll be about the first before the lutier can help me remove the bridge, so limited on how much I can do on the front. Figure do the 220 sanding on the back & sides, get as much of the front as I can, and wait for the finer sanding until the bridge is out of the way. I'll add some pictures later, guitar and scraper.

Updated: here's the scraper
As mentioned before, this is a piece of handsaw blade.  I don't think I've covered making this before, so:
First, figure the size & shape, and cut it.  I used a dremel with a cutoff wheel: draw the outline, cut just outside that line.  Don't have to cut all the way, depending on how you lay it out: if you score it deeply enough, you can then clamp it in a vise and flex the blade to break the piece off; same for smaller pieces to get the shape.  For a curved face, you'll have to do some grinding: I use my belt sander to both smooth & true the flat sides, and shape the curve.

Remember that you need the edges to be as square as possible, with sharp corners.

With a new piece, after the profile is done I lightly sand the flats to get rid of any burrs, then roll on the hook.  From here the pics are for putting a new hook on one you've been using:
First, use a fine file to cut away what's left of the hook.
Then use the file to cut the side down.  Again, keep it at as true a right-angle as possible to the scraper so you get those nice square corners.
With that done, I give the file a wipe over the flats again to get rid of any burrs.  Now comes making the hook.

Clamp the piece in a vise, and you'll need a hard, smooth piece of steel; in this case I'm using a long hex key
  You can buy a burnishing tool for this, it's a oval cross-section piece of hardened steel with a handle(yes, I need to make one) just for the purpose.  As long as it's smooth and hard(you're working on a piece of medium-to-high-carbon steel, remember) it will work.  Hold the tool against the scraper starting at one corner(in this case) at about a 35-45 degree angle.  Now you have to both push or draw it along the corner while pushing the tool down, actually sliding it both horizontally and vertically.  What you're doing is forming that corner into a hook that extends out a bit; light pressure can make a barely-there hook for very fine scraping, heavy pressure makes a bigger, more aggressive hook.  Takes a little messing with, but it's easy to pick up how to do this.

I learned this from a guy I used to know named Eddie, one hell of a carpenter/woodworker/general craftsman who had no problems sharing knowledge.  A fine man, died a few years back(yeah, he's missed by a lot of people).  He used scrapers a lot, both for removing old finishes that tended to clog sandpaper fast, and for the wood itself: set up the right hook and you can either take a fair amount of wood off with each stroke, or barely touch the surface to smooth it.

Back to the guitar, here's the soundboard; aside from a small place at the top, this along the bottom was the only places the finish was separating. 
 Just to try, after it sat all night I tried the scraper carefully along the edges, and sure enough was able to pop off more of the old finish.  After that did some sanding.  By the time my hands were saying "Knock it off, NOW" I'd removed a fair amount of the finish on the soundboard and done more 220 sanding on the sides and back
Sides and back are starting to look nice.  Be a while yet before I can get the gentleman to help remove the bridge, so no rush on this.

By the way, if you're looking for instrument parts/materials/finish stuff, here's the site he gave me: Stewart MacDonald.

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