How to slim down a neck

[bud]

I'm working on converting an old archtop SS Stewart to a mandocello. I'm stuck trying to figure out how to slim down the neck. At the nut the current measurement is 1 13/16 inches. I'd like to get it close to my bouzouki measurement of 1 7/16 inches. It is a bound fingerboard so I have already removed the binding. I also removed the frets and leveled the fingerboard. What's the best way to cut down the width by 1/8-3/16 per side down the length of the fingerboard? Thanks in advance.

[sunburst]

The first step is a center line. Draw one, or lightly scribe one down the center of the fingerboard. That's assuming the neck was centered to start with. If not, here's your chance to correct any missalignment with a new center line.
Then figure out your final width and draw or scribe those two lines the full length of the neck.
Now cut away everything outside of the lines and reshape the back of the neck to the profile of your choice.

If you are pretty well tooled-up and brave enough, you could start with a band saw or belt sander, I think my tool of choice for most of the wood removal would be the Stanley surform. Use a straight edge on the sides of the neck to be sure they stay straight as you get down to your lines.

Where the neck joins the body, you're pretty much on your own. The choice of tools and procedures is probably as varied as the people who might try the job. Files, chisels, knives, whatever.

[Eugene]

One thought is to not thin a 6-string neck to carry four courses of paired strings, but leave it at thickness to carry five courses of paired strings. There is precedent in a mandokin popular in Europe in the late 1800s-early 1900s called the liuto cantabile. It was a mando-cello, but carried an extra course at high e' to accommodate solo literature. You might want to consider such a 10-string cello, courses tuned, low to high C-G-d-a-e'.

[bud]

Eugene, I'm definitely sticking to an 8 string for this instrument.

Sunburst, you are suggesting eyeballing this to get it straight along the line. I thought it might be possible to do this with a jig and a router. Any thoughts appreciated. I will have to come back after cutting down the sides with a router to cut my ledge for the binding.

[sunburst]

You could probably set up a router jig. I bet I could have the job done by hand before I could even figure out how to build the router jig tho. When you consider that you're not going to do this very many times, a router is not something I would consider. Besides, I hate the sound of a router and I don't really consider working to a line "eyeballing".

As for binding, I would cut the sides of the neck to my lines and roughly square to the fingerboard,(I say roughly because I assume there is a radius on the board), cut the binding slots, glue the binding and let it dry, and then finish shaping the neck. I might use a router for the slots, but there would be parts of it that might be hard to get too, so I might use my perfling cutter.

I thought of a router method:
Make a "dummy" fingerboard the size and shape you want, fasten it securely to the surface of the existing fingerboard in exactly the right place,(double stick tape? hot melt?) then use a flush cut bit with a guide bearing running against the edge of your dummy fingerboard to cut the sides of the neck.

[Dolamon]

One thought regarding nut width Bud ... are you going to string this with a "normal" Mando Cello set? These have some really hefty strings on the C and G courses, before you trim the neck you may want to rethink the width of the strings at the nut. It may need to be a 1/16th to an 1/8th wider.

[douglas2cats]

Unless you're very careful and sneak up on the cuts with the router you'd probably be a lot better off at least bandsawing to within 1/16th (or less) inch of your cutline first before switching to the router to clean up the cut. Otherwise you might risk some pretty severe tearout given the amount of material you're trying to remove. I'd also cut some wood shims the thickness of the fretsaw kerfs and jamb them in the slots before I tried passing a router bit past them. Otherwise you'd probably get tearout along the FB edge at each kerf.