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So I'm sitting here admiring my just completed guitar and it so happens that the light is reflecting off its neck at just the right angle, and suddenly I notice a few undulations. Waves. Bumps. They're quite minor, but they prevent the neck from having a perfectly smooth contour.

And I was so sure I had worked a smooth contour into this one. Grrr . . . think again.

I use spokeshaves,followed by rasps, followed by sandpaper when I contour necks, and you know, when they're "in the white" they feel perfectly smooth. It isn't until I get some finish on them that I see, rather than feel, the slight imperfections. But then once I know where they are, I can feel them too.

So, what do you guys do for this? How do you achieve a perfectly smooth contour with your necks?

Best,

Michael

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Live to Play, Play to Live

I use scrapers, rasps, planes, spokeshaves for most of the shaping, then sanding blocks with sandpaper and smooth, unidirectional strokes to make sure everything's level (and check with my fingers, which do tell me more than my eyes, and with a straightedge against a backlit source). I also 'shoeshine' to smooth everything out using stiff cloth-backed paper (or better, the kind of paper that's used in sanding belts), being careful to move back and forth evenly, and not applying too much pressure.

None of the edges tools really do the best job of smoothing out slight undulations; a flat sanding block of some length is the only reliable way I've found to do that quickly.

I attached a long hobby shop, aluminum sanding plane to an orbital pad sander. With 60 grit paper it only takes a couple of minutes to flatten the neck shaft.

Okay, it appears that all you guys use some sort of sanding block somewhere in the process as a means of smoothing out the slight undulations. I have been trying to do the same thing using long rasps, but I'm willing to try something else. I can fabricate a longer sanding block easily enough. Just wondering if you consider the standard sized hard rubber sanding blocks to be too short?

Best,

Michael
Michael McBroom38631.4325810185

_________________
Live to Play, Play to Live

Michael, do the bumps run lengthwise? I use straightedges to check that the neck is flat. Hold the straightedge to the neck, hold it up to a strong light, and check that you can't see any light between the straightedge and neck. Rotate a few degrees and check again.

It the undulation is across the short dimension, then take a straightedge, hold it perpendicular to the neck, and shine a strong light source on it so it casts a shadow over the neck contour. This curve should look perfectly smooth. If it isn't, you have a bump in the neck. Slide the straightedge along the length of the neck, making sure the curves are fair the entire length.

You can also use this shadow technique to find imperfections in the heel and in the curved join of the headstock. It's often the only way I catch these errors before applying finish.

As for your question about sanding blocks, just cut a piece of plywood just slightly shorter than the length of the flat part of your neck. I use the 3M rolls of sandpaper sold by StewMac, so I cut the block the same width as those rolls. 120 on one side, 220 or 320 on the other. Takes just a minute to make the block, and another minute to replace paper as needed.

Another thing I use is a light source on an articulated arm - one of those desk lamps. That way I can easily move the light source around as I work, which makes it easy to change the shadowing. Try to get a good shadow cast on the part you are working on, and you can see any imperfections much better. This is much faster than unclamping the neck, holding it up to the light and rotating it around. Move the light, not the neck/guitar.

After removing the bulk of material with spokeshave, rasp, coarse file,
and smooth file, on the straight section from nut to 10th fret or so, I use
wooden sanding blocks that are about 5" long x 2" wide that clamp the
paper at each end. Using them ensures an even and straight neck shaft. I
also have several that are 1" wide for narrower uses. For the curved areas,
such as the heal and transition area from shaft to headstock (again, after
filing), I use a piece of fairly stiff felt about 5/16" thick with sandpaper
wrapped around it. The felt has enough give to it to conform to overall
curves, yet it is stiff enough to ride across the smaller valleys and
inconsistencies and knock down the "peaks" until there are no more
valleys and peaks, only sweeping, smooth curves.

Here's a drawing of the block. It uses 2" wide strips cut off a standard
sheet of sandpaper.