One of the more scary tasks completed; the angled route for the knob potentiometers to fit the arched top.
Funny enough my curiosity about how this was done is actually what sparked my whole interest in actually tackling this project, even though it’s a portion of the instrument you shouldn’t often see and makes no difference in playability or tone, its multi step process creates an interesting to look at cavity, and just like with cars I care how things look under the hood!
This is how it’s done
A wedged jig clamped at an angle that roughly corresponds with the arch of the top, eg it’s not actually different usage of the router to flush cut it on a template, but this time with wedges.
The scary part is this is the router bit it I used
Note that I’m hardly reinventing the wheel with this project, I’m simply using plans I got off the internet using the well beaten path of processes many luthiers came up with up to 40 years ago building burst replicas. What they don’t usually use doing it though is a cheapish router with no speed adjustment and a 1/4” shank to do tasks such as this. This bit is pure Chinesium and not by choice or frugality(well, putting aside the option of buying a higher end router anyway), but because no other reputable tool maker makes 2” long router bits meant for a router shank this small! Lots of room for fail spinning this thing 24,000rpm on an uneven diagonal side load. But I did it, slow and steady.
And that blue masking tape? The quality of this bit is such that the cutting blade sticks out about a thousandth past the bearing on one side, so I had to tape it to prevent overcut. That unevenness put the bit out of balance too so the whole router was a bit more shakey!
Now that the recess is made to get the holes for the potentiometer shafts to equal depth, I need to clearance the sides for the them. I toyed around with a few methods tonight but this was the simplest
I simply drilled a few snug holes into the same template to hold a 1”forstner bit and aligned it with the pilot holes. Nobody quite knows how Gibson did this on the originals but it was definitely a separate step from the larger route since these leave distinct tooling marks on the walls. Actually that chew mark left in the one I took a pic of drilling is one of the ways appraisers authenticate the real ones, older replicas and modern reissues either don’t leave them or leave too clean of marks. Forstner type bits uniquely chew the edges, so I went for that extra authenticity