Official Luthiers Forum!

Just wondering how many different ways are out there for putting the radius on head and tail blocks where they glue to the curved rims?

I know some use:
- large disk sander
- a plane
- belt sander
- sine table with a sander

What is your detailed approach for accuracy and ease on this step?

Thank you!

A cool way that I learned back in the day was to make a positive of the radius I want and then slather on Bondo to a block of wood, cover with waxed paper and press it onto the radiused form and leave until the bondo dries. I still have my blocks I made this way and they have yet to rust.

Hesh, that sounds like making a radius block for sanding a fretboard radius - ?
Think OP is asking about fitting neck and tail blocks to sides.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Because my moulds are over full height at neck and tail (detachable add-ons) I just use a block plane to rough them in, then sand them to final shape with self adhesive abrasives stuck n the mould.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I draw the radius on the top and bottom ends of the blocks using a radius template made off the body plan and then sand to the lines free hand on the belt sander. My belt sander is set up vertically and I set the table perpendicular to the belt. I rest the block on the table for the sanding and flip the block end for end a couple times during sanding to make sure I don't go past the lines. It's very fast and accurate and doesn't require a jig.

Example of a head block. (I rout out the head block mortise before sanding the radius.)

_________________
Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I use a hand plane followed by my fretboard radius blocks. In some cases it's perfect in others it's close enough to finish on a sanding bard.

You can make radius blocks for anything this way, with Bondo. I would do what J describes and rough in with a plane but then I went to my blocks to refine the shape.

Mine had double duty as clamping cauls and radiused sanding blocks.

I use my mold.
I cut plane the edges of the block close... then I stick tape to the inside of the mold and use that to finish the shape


Sent from my iPhone using Tapatalk

I do pretty much exactly what Jay does. I have cnc cut acrylic templates for all of my guitar models so it’s easy to accurately mark the radius on the block and head to the 6”x 48” sander and sand to the line. I do the same for the plywood tail block.

My thinking is that I’m gonna be within .002-.005” of perfect doing it by eye. Any slight adjustment will be handled during final fairing of the sides before cutting the binding ledges.

Best, M

I also use my acrylic templates to mark the blocks then just sand on a 12" disc sander. Quick and easy.

_________________
Steve Smith
"Music is what feelings sound like"