Building a Double Bass: Shaping the Blocks

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Shaping the Double Bass Blocks

Lots of Wood to Move!

As you may recall from the previous post, the blocks on this upright bass were pretty huge, compared to what they needed to be, so there was really a lot of wood to remove.

Mold with blocks and ribs

Mold with blocks and ribs. Blocks are still way oversized, and the ribs are still straight. Gotta change all that.

 

“Kutzall” Tool

So! A drastic need makes for drastic measures. Ordinarily, on a smaller instrument, I would use the bandsaw and oscillating spindle sander to shape the blocks, but this  mold is reeaaalllly heavy (over-built, I think…oh, well, it will be removed and the bass will be normal), even though it is a soloist bass, so I can’t see trying to manhandle it around on my big bandsaw. The saw could handle it, but the table for the saw is not big enough to hold the mold steady, and I am not strong enough to just hold it up there by sheer strength…. So… what to do?

This tool (carbide abrasive disc) is something my wife bought for me a year ago (Christmas), but I had never used it much. It is called a “Kutzall”, and it tears away wood incredibly rapidly, without loading up, and without burning the wood. So I used it to remove the large rough sections, then used the plane to remove the torn surface, and finally, to shape the blocks:

Kutzall disc, with 5

Kutzall disc, with 5″ DeWalt angle grinder: Not for the faint of heart! Absolutely wickedly effective, but not as dangerous as the Lancelot tool.

 

Stanley #100-1/2 Squirrel-tail Plane

It was about 37 degrees, F, outside, but the sun was bright, so I worked outside.

Smoothing and shaping the corner block

Smoothing and shaping the corner blocks, using a Stanley “Squirrel-tail” #100-1/2 hand-plane.

 

The little plane is somewhat hard to control, because the curvature of the sole is so extreme, but, if it is sharp and if the blade is set for a very shallow cut, it works well.

sharp plane

It does have to be sharp! (Time to sharpen….)

 

Stanley # 100-1/2 curved-sole plane

Stanley # 100-1/2 curved-sole plane…for those of you who are unfamiliar with it.

 

stanley plane

I was able to shape the blocks pretty close to finished shape with the little plane, but there are some irregularities. I have another tool for that problem.

 

The bottom block was planed entirely with a low-angle plane (also Stanley– can’t recall what number.) but it worked very well, and the bottom block was easy…I didn’t use the grinder at all on this one. So here are all the blocks, pretty close to finished:

Bottom block planed with a small, flat-sole, low-angle plane.

Bottom block planed with a small, flat-sole, low-angle plane.

 

And, here you can see the finished blocks, ready for sanding:

All the blocks, ready for coarse-sanding.

All the blocks, ready for coarse-sanding. The small plane leaves ripples. The sanding tool should remove them all.

 

Homemade PVC Sanding Tool

As I mentioned earlier, the oscillating spindle sander I have would not be tall enough for these blocks even if I could manhandle the mold up onto the machine. So, I made this little sanding tool out of re-claimed PVC fittings from the “Habitat for Humanity Re-Store”, and spent more on the little can of PVC cement from the hardware store than I did on all the other materials…about $2.50 at the Habitat store. I used PVC cement to affix the abrasive cloth to the pipe, too, and bound it up with strips of plastic bag until the solvent outgassed and the cement was set.

PVC sanding block

Sanding block fabricated from four PVC fittings and a 2″ section of 2″ PVC pipe, with a little piece of wood for the handle grip. Comfortable, efficient, and cheap.

 

The homemade sanding tool worked extremely well for the small corner blocks, and did very smooth work. On the neck block I used it cross-grain, holding the tool parallel to the “trough” of the curvature, and sliding it up and down the curve. It worked well, there, too, just not as perfectly as on the corner blocks. All in all, it is a very satisfying tool.

Sanding corner blocks.

Sanding the corner blocks.

 

Sanding the neck block,

Sanding the neck block, I kept the block parallel to the “trough” of the curve, and pushed it up and down, across the grain to get a smooth surface.

 

Change of Plans

You may have noticed that, though I had planned to use Willow for blocks and linings, those blocks are not willow: the corner blocks and end block are all Douglas Fir, and the neck block is laid up of three layers of clear, vertical grain Sitka Spruce. It was a matter of availability. I do have willow for the linings, and, as that in my preferred wood when I have a choice, that is what I will use. It cuts easily, bends easily, and is very pleasant to work with for both linings and blocks.

I have really felt that I was “spinning my wheels” on this project. It is large enough that I feel the necessity to work outdoors whenever possible, but the weather has not cooperated very well…it rained nearly every day for the last month. In addition, I have been struggling with a cold or some such virus. Today I was cold in the house when the thermometer read 75 degrees, so that is not normal. I finally felt a little better, this evening, and went outside for the few minutes it took me to sand the blocks, but it has been cold out, so I didn’t stay long.

Ah, well, that’s life. I’m grateful to be back on the project again.

Thanks for looking.

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4 Responses to “Building a Double Bass: Shaping the Blocks”
  1. Chris S. Hadfield
    12.01.2015

    Wow, I thought you were building a large bass and it looks like you certainly are. Very impressive from anyone’s standpoint I would imagine. Your so talented. Chris H.

    • 12.02.2015

      It’s coming along slowly, but I think it will be a good bass. Have to wait and see. Thanks for looking.

  2. James Carroll
    12.02.2015

    Hey Chet….. You are more of a man than I am, working out side at 37 degrees ! Double base looking good, can’t wait to see it when it’s finished !

  3. 12.02.2015

    Well—as I said, the sun was bright and made it feel a little warmer. On the other hand, I have been struggling with a cold, and that probably did not help.


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