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I decided that the plain mahogany back for my parlor project needed some help, so I routed a channel for a dark stripe of African black wood I had. Used a down spiral cb bit set at half thickness and it tore up the edges of channel. Went ahead and glued the BW strip and then tried filling gaps with mahogany dust and TB 3. Doesn't seem to be working out. Suggestions??? Picture to follow.

I would think the best thing to do would be either rout it out and install a new strip or carefully rout out along the edge of the Blackwood a strip wide enough to cover the tear out and install some purfling strips. Of course the later will complicate the side and back binding and purfling schemes, but may end up looking the best.

My last guitar I think I had to put in three different back strips for various reasons so I do, unfortunately, speak from experience.
Kent

Ed : Not much help in your situation but I install back strips in the glue up. Saves the work and hassle.
Tom

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A person who has never made a mistake has never made anything!!!

I prefer to laminate them between the back plates to prevent such tragedies. I suppose it could cause structural issues, depending on the inlay strip composition, but the back graft helps mitigate that.

Possible fix - square up the tear out against the inlay and chamfer/bevel it down from the outside towards the inlay with a chisel.

Then cut and glue a thin wedge of mahogany in its place.

Once it dries, plane and sand to contour.

Thanks for the feedback. I knew I was taking a chance. I have some purfling I may add if I decide to route out the damage. Live and learn.
Ed

Add something like Sam Guidry's back inlay? http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=45740

If the back is still wide enough, you can redo it. Heat it up, pull it, or cut it out and re-glue and inlay or squeeze it in. Are you using a wide bit in 1 pass or a smaller one with many passes? You must be going against the grain on that one side and making it chip. Mahogany chips out a lot easier than say walnuts or rosewoods. And harder to hide any gaps.

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Jason Moe
LaCrosse WI 54601

I missed the TB part. That won't work. You could try epoxy or CA with the dust, but you may not like the look.

I like the chisel idea. I have some green purfling that I bought cause green is my grandson's fave color. I'll try to add some to each side of stripe. Thanks.

One way to prevent getting tearout is to make a zero clearance guide for the router. Tack a fence onto a piece of plywood that is 4-5" longer on each end than the guitar back, and rout through the ply with the router against the fence. Line up the opening of the ply to the location to be routed, attach with a couple of tabs of double side tape, and rout with the router tight to the fence. As long as the ply is tight to the back, there won't be any tearout.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

Like Alex I'd be focused on the cause of the tearout and not having it happen again. Sharp bit
in a runout free spindle should yield only crisp edge inlay channels.
For your present situation, asuming enough width, I would rip the back both sides of the strip, sand
the strip back to desired thickness, rejoint and glue up the panels, then inlay the strip again.
The method Alex suggests is as "simple but effective" as it gets. Also, I would recommend running a few passes on something other than your precious back panel to nail your proceedure. Good luck with it.
Ken