This is what happens when I try to make my own jigs

[Ben-Had]

This happened when routing the binding and purfling channels. I made my own doughnut on the bottom of the router plate to ride the slope on the top and back to keep the router perpendicular. Got the test cut depth/width right for the purfling/binding channel (.120 purfling and .060 binding = .180 wide & .065 deep) Cut purfling channel. Looks great. Measure for binding channel (.060 wide and .200 high). Cut binding channel. Oops!!! The doughnut rode in the purling channel instead of rising up to the guitar top and cut the binding channel too deep and too narrow. Now I can recover from this with a higher binding (.250 whew). But I don't want to do this again. I am using the Stewmac router bit and bearing set with a tower binding jig. Should I have cut the binding channel before the purfling channel instead of the other way around or maybe my doughnut did not have enough length of material out on front of the bit, if that is the case can someone recommend a doughnut size that's right.

Any suggestions appreciated.

[tippie53]

I do the wide cuts first maybe you missed the flat area on the taper????

[Kevin Sjostrand]

Yeah, you have to have a flat area up to the bit of around 1/4" to 3/8"...something to ride on the top edge.
If you have enough, it won't matter in what order you cut your channels.

Kevin

[Ben-Had]

Yeah, you have to have a flat area up to the bit of around 1/4" to 3/8"...something to ride on the top edge.
If you have enough, it won't matter in what order you cut your channels.

Kevin

I think that's it Kevin. My taper went to the edge - NO FLAT AREA -AHHHGGGGG.

[tippie53]

I have to say yes it does matter . I have a set of bearings that is I do the binding first I loose contact on the side. You have to be careful . If your bearings ride lower on the side it won't matter.

[rienk]

Of course, I'm a do-it-yourselfer with a full tool shop, so I'm building all my own stuff.

[tippie53]

Call me I think I can help
You need 2 things to make the unit be most efficient
1 The donut , that has to be high enough to clear the plate and angled enough to only contact as few points as possible.
Here is part of the equation , if your donut allows the cutter to cut part of the track , your next pass will be riding on the wrong points, so the angle needs to ride as close to the cut area without getting onto that area.
2 The base needs to be adjustable so you can make the sides as perpendicular to the table as you can. Also if you are using a non pilot cutter that uses and adjustment arm or pilot to set the width of cut , you have to be very aware that you cutter stays tangent to the pilot. Any variance off the line can change the width of cut.

I also like to use .0625 think binding and set the cutter so I am just into the side and sand the side to the binding not the binding to the sides

[sylvan]

One improvement I would suggest you make to your binding machine is to make a new donut which, by its' design, cannot destroy your work if you make a mistake. That donut is constructed with a 1/4" ledge which is flat and then the rest of the donut tapers away from the edge. The taper amount is not critical it just provides a downward ramp if you make a mistake. If you let go or somehow lose control the shape of the donut moves the spinning bit away from your work. It works so well that I have my students cut their binding channels blindfolded!
I have enclosed a photo of the modified donut so you can easily make one (with a lathe or a table saw).
I also agree with John that you want to cut the channel slightly wider than you need so that when the binding/purfling is glued in place you actually sand the side to the binding and not vice versa. I always add .010" to whatever the thicknesses of the pieces are for purposes of cutting the channel.

[Darryl Young]

Seems if you use bearings on the bit, then you need to cut purfling channel before binding so you don't loose contact with sides. On my setup, I have full side support (don't use bearings) so contact between the doughnut and the top/back is more important so I cut binding channels first.

This reminds me of other areas where you have to pay attention on what is done first while building. On my first guitar, I cut the binding/purfling channels and installed my binding before fitting the neck.......so I didn't trim the sides away from the neck mortise till after binding was done and I had no problems. Since I've seen others rough fitting the neck on a dreadnaught prior to binding without issue. Well, on the 00 I'm working on now, I thought it would be neat to bolt the neck on and see how it fit my daughter (ok, I wanted to see it and get a feel for it as well as I've never held/played a 00) so I removed the excess side material above the neck mortise and had fun bolting the neck on and my daughter got a kick out of holding her guitar and seeing how it would fit.

Good times.......until I routed the binding channel on the back <smile>. What was I thinking??? Ha! The height of the sides on a 00 is shallow at the neck........so much so that the mortise extends up into the binding. So the side guide on my binding jig fell into the mortise while cutting the binding channel cutting through the side and into the neck block. Idiot! <smile>

Oh well, that repair was fun but I finally worked through it.

[tippie53]

There is another benefit of purfling first .
Look at this , when you are cutting through the top with a bit you have a higher risk of tear out . So the wider cut isn't going through the top and it is self supporting so you have a lower risk of tear out. Then when you do the binding , you have now a weak zone so that if tear out occurs it most often happens in the line of the purfling cut and not the visible top.