Post
by Arnt » Mon Nov 05, 2007 6:17 pm
Hey, that looks familiar! Good job, your jig should work well.
Martin has some good suggestions, here are a couple of additional thoughts:
In your jig, the movable 'shoe' (the vertical plywood part that the bearings are attached to) has a pretty small contact area with the horizontal plywood base plate. I would be concerned that this joint might not be rigid enough, and that the two parts could flex a bit and not remain square in relation to each other, possibly leading to an non square binding rabbet.
I prefer to use a down cut spiral bit, I think it cuts cleaner than a straight bit. I use 1/4" carbide down cut bits from LMI, but you may find them less expensively locally.
I have had better luck by placing the jig horizontally in a vise and feeding the guitar to the tool than using it hand held, which feels a bit unstable to me. This may sound scary to some, but this principle is used in many of the big guitar production factories (Martin, Taylor), and I feel it gives better control over the process.
To avoid blowouts, I cut from the widest parts of the bouts towards the waist, then towards the blocks, and finally a single pass around the entire instrument.
Consider recessing those screw heads in your base plate; they could easily ding a soft spruce top should they come in contact with it...
Good luck!
Arnt Rian,
Norway