Tooling question...

[Andrew]

Okay, so I'm thinking my next build may be another like the one in my avatar (I'll attach a larger pic). And I would like to have my local tool shop make me a cutter that will carve out the bowl shapes surrounding the control knobs . Carving them by hand is miserable work. It would probably be a good idea to have the design basics figured out before I have the thing made - problem is, I dont know squat about making cutters for power tools, so if anyone here feels inclined to point me in the right direction, that'd be cool beans.

Some thoughts off the top of my head:

- I think a tool I can use in my drill press would be ideal
- the tool should perhaps have a brad point, to keep it centred in the cut and make locating it simple
- the cutters would be shaped more or less like a cove bit for a router
- should there be two cutters, like a standard router bit? 3? 4? More?
- should the faces of the cutters meet the wood at 90 degrees like a router, or be angled back somewhat, more like a forstner bit?
- what would be the ideal relief angle, given the angle of the cutters
- HSS would probably be ideal I think. Something I wont have to sharpen very often, but will still be relatively easy to sharpen (and a great deal cheaper than carbide).

Anything I'm missing here? Should I just buy a few good gouges?

[Russell Vance]

Hi Andrew,

Why not just use a circular template and the attached round-over bit to machine your  recessing.  You need a router to do this but it'll be cheaper to buy a router and the round-over (or cove/bowl-makers bit) bit than to have a tool made by your local machine shop.  Large diameter cutter do not work very well in drill presses because of the chatter and grabbing problems.  Using a drill press and cutter in figured wood will exacerbate the problem.   Forsteners work because their center point guide is subjugated by the bore wings which act as major guides as the tools cut.  

Alternatively, if you feel that you must go the drill press route just grind/machine a profile onto a hole-boring spade bit and practice a bit (or a lot).

Rusty.

[Andrew]

Ill definitely give these a shot, especially seeing as I already have the routers and bits. I guess I was visualizing a tool that would work somewhat like a countersink - but yes, they can definitely chatter. I was hoping for something a little more 'chuck up and go' than a bit involving templates, but I can see how that would be potentially unsound.

[Robbie Collins]

Also remember that, if the guitar top has topography like a Les Paul, then a drill press will not drill a hole perpendicular to the top because the slope is different at each pot location. You could use wooden wedges to tweak the angle of the dangle but a plunge router would tend to be tangent to the slope at any point with some eye-balling.

[Andrew]

Yes, thats definitely another concern and a bit of a complication. If the bowl bottom is perpendicular to the arch of the top, then the control knob may not sit correctly on the pot post, so the bowl must be perpendicular to the back of the guitar, more or less. I say thats a complication because that guitar was carved by hand on the fly, tweaking things here and there as it suited me until everything lined up nicely - which was a trick in itself because of the way the bowls intersect the outer 'bevel', on top of having grain running in every conceivable direction. Ill have to do some more planning if I'm going to use a router I suppose... Of course, if the router does the bulk of the waste removal well enough then fine tuning by hand would be a breeze compared to the way I cut them the first time.