Upright bass - challenging project

[germanguitars]

Making an upright bass - the neck has been a very challenging but rewarding exercise.

I cut out a few test runs using knotty cedar fence rails in order to identify the most likely tear-out locations. Along the bottom of the scroll it really wants to blow out the edge, so to preserve that I used the 1/4" bit to drill overlapping holes there instead. Worked like a charm. The shape is cut in two halves from 1.5" thick blanks, and plunge roughing using a 1/2" up spiral end mill is definitely the most efficient way to go.  

[dustypilot]

Very pretty. Look forward to seeing the finished product.

[craigo]

As a doghouse bass player, I'm thoroughly impressed you're even attempting this.

[germanguitars]

Archtop guitars have pretty similar construction to the violin family. The scroll and pegbox is the biggest difference so far. Side bending wider boards will be tricky (but easier than a tight cutaway horn on a guitar) along with a more complicated body mold. No real difference with the process of carving the top and back plates.

[germanguitars]

Took 1 hour to rough the interior using a plunge operation. 1/2" 2-flute spiral ball nosed bit at 60 in/min

The finishing pass took about 30 minutes at 120 in/min

(this bass is skinny - same length and depth of a typical 3/4 acoustic, but it will be very narrow. Intended to be plugged in, but this is the only way to get good acoustic tone)

[mikedoes]

Sept 6, 2021 17:43:11 GMT -5 germanguitars said:

Making an upright bass - the neck has been a very challenging but rewarding exercise.
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I cut out a few test runs using knotty cedar fence rails in order to identify the most likely tear-out locations. Along the bottom of the scroll it really wants to blow out the edge, so to preserve that I used the 1/4" bit to drill overlapping holes there instead. Worked like a charm. The shape is cut in two halves from 1.5" thick blanks, and plunge roughing using a 1/2" up spiral end mill is definitely the most efficient way to go.  

View Attachment

How did you create the part drawing?
I’d like to see a video of you creating it.

[germanguitars]

I model everything from scratch in Rhino. I was trained as a medical illustrator/3D animator in the early 90s and I've done a *lot* of 3D modeling. Feels like sculpting clay to me at this point.

Creating a model of an arched plate is tricky because many strategies create wrinkles where you don't want them.

[germanguitars]

Plunge milling really works well for 3D objects that require hogging off a lot of excess wood. It also saves a lot of wear and tear on the machine: Much less X & Y travel, and the cutting only occurs in the Z axis. No sideways force on the spindle bearings, either.

The other nice aspect about plunge milling is that it keeps the bit cooler (as long as you get your feed rate right) because of the 50/50 air time. If you drive it too hard, skipped steps would be on the Z axis and result in too little wood removed, as opposed to a skip in X or Y resulting in ruin. 

[germanguitars]

After carving the exterior of the top, an ugly sap well appeared. I excavated it like a dental cavity and inlaid a piece of neighboring spruce in the same orientation. Should be almost invisible under shellac. The knot near the f-hole is character that will have to stay.

[germanguitars]