Router Jig for Radiused Fretboards

The original jig is very elegant. When I thought about it, I realized that one does not need to make full convex sides for the jig to slide upon. Two points are sufficient to make the top concave arc slide in a circle. With this in mind I made a modified jig out of 3/4" PVC pipe for 'rails' (very uniform, and slippery), and the arc plates I cut out of acrylic on a laser cutter. I put a threaded insert in the top and drilled a hole in the acrylic baseplate I use with my trim router so that I can simply attach the trim router with no need to change baseplates or anything. Works great. Here are some pictures, and a measured drawing I did first to get the dimensions reasonable.
 

Attachments

  • IMG_20171019_095050.jpg
    IMG_20171019_095050.jpg
    96 KB · Views: 81
  • IMG_20171019_095145.jpg
    IMG_20171019_095145.jpg
    94 KB · Views: 66
  • measurements.JPG
    measurements.JPG
    22 KB · Views: 57
That'll work! I've seen other versions of this jig that use pipe in the same way, so presumably, others are getting along just fine with your approach.
 
Firstly, with this type of jig I've read that routing across the grain can be problematic with tear out, so do you rout lengthwise up and down the board, turning the radius a touch each sweep?
And what size and type of router bit is used for the best results? Thanks Mike
 
I've never seen any tear out using a Freund 1/2" diameter straight bit with two carbide flutes. Some woods may be more prone to this but it hasn't happened with West African ebony, Macassar ebony, EIR, maple or the junk fir that I used to test the unit when it was first completed. I move up and down the board lengthwise using quite a few passes, probably a dozen or more, and always radius before cutting the fret slots to avoid the possibility of chipping the slot edges. I don't know how much of a risk this is but my process of cutting the slots doesn't care if the board is flat or radiused so I do the slots last so there's no risk at all.
 
I use a large 1/2 inch Triton Router and this bit from Wealdon, a surface trim bit and I use the 50mm one.

https://www.wealdentool.com/cgi-bin...atalogue_Surface_Trim__3_Wing_250.html#aT2410

I take a run lengthwise up the middle of the board then take alternate runs up and down either side. I never rout across the grain. The bit I use is good because the curved outer edge doe not dig in so you don't get tram lines like you can sometimes with a straight cutter. I also radius before cutting fret slots or tapering the board blank. Bob
 
Top Bottom