Bone Grafts for Problem Nut Slots

Last of the nut stuff for now. I thought I’d follow up the last few weeks worth of information on shimming nuts and filling slots with something a little more involved and — truth be told — a little less common.

Grafting fresh bone into a worn or ruined nut slot.

Recapping on things, we generally choose to shim under a nut or fill a problem slot when we have some reason not to replace the nut (which is generally the more ideal solution). Sometimes, this is a monetary concern or sometimes we just want a quick fix. And, sometimes, we’re faced with a guitar with some vintage mojo or value and we just don’t want to install a new nut.

This last circumstance is probably when you’ll employ a bone graft.

We can even fix a slot that’s THIS screwed up.

Nut repair with a bone graft

Filling slots and shimming nuts is all well and good. But if the slot is really messed up, these methods might not do the trick. For badly cut slots that are really deep or — more likely —  are cut really wide so that the string can slide about from side to side, we might restort to a bone graft.


It’s possible to glue in a new piece of bone to fill the problem area.

Check it out…

First widen the problem nut slot to accept the bone graft.

First off, we need to clean up the slot and make it into a regular shape. Doing so means it’s easier to shape our new bone graft so it fits. So, use a file to widen and even out the problem slot. A needle file will probably work for this — even a square one would give nice even slot walls — but I’ve used a larger (bass-nut size) nut file here.

Use some scrap/donor bone and shape to fit your widened slot.

It’s easier to fit your ‘graft’ to the slot than the other way around so, when you have a nice even slot, begin shaping a bone off-cut to shape. Use some 220 grit sandpaper on a flat surface and get the with right so the graft fits snugly in the slot. Not too snugly, by the way — it’s easy to split the nut if you have to force things.

When the width is good, work on getting the bottom shaped for a good fit. As I mentioned, I like using a rounded bottom here which means a bit more work in fitting the graft but I prefer the end result.

Trim the excess, leaving your graft piece a little larger than the edges of the nut.

When the graft is fitting well, use a pencil to roughly mark the area to be inserted and cut off some of the excess. At this point, don’t worry about getting these cuts so they’re flush with the nut. Well tidy that up later. For now, just hack off most of the unwanted bone and leave enough to easily handle.

I use the medium viscosity superglue for this job (that is, the ‘regular’ stuff you’ll buy pretty much anywhere). Splodge out a little blob onto a piece of plastic and use a toothpick or bent-over guitar string to ‘paint’ the inside of your slot walls. I’m pretty liberal with the glue at this point (but be very careful if you’ve been brave enough to do this with the nut still on the guitar).

Quickly pop your graft into the slot and, if necessary, hold it in place. A little superglue accelerator is fine on this job.

Glue the graft piece into the nut.


Once dry, you can use files, sandpapers, and polishing compound to clean up your grafted-in bone so it matches the original as much as possible.

Then you just need to cut a new slot and you’re in business.

Bring the grafted piece flush all around and you’re ready to cut a new slot.

As I said, this is a bit more involved and likely not something that many readers will have to do. The requirement for ‘scrap’ bone pieces probably pushes this towards the more professional end of the DIY spectrum but, if you have the parts and tools, it’s a relatively straightforward job and well within the realm of most. You may never have to use it but maybe it’ll be one of those things that gets filed away at the back of your brain where it’ll surface in forty years to save the day. 😉

One last consideration. Obviously, this solution is aimed at bone nuts. Many plastic and synthetic nuts don’t respond so well to superglue and you may not get a good bond that will hold over time. If we’re talking about retaining vintage vibe, we’re probably not talking about plastic nuts, though, so it’s likely fine. There won’t usually be the same pressures to avoid replacing a synthetic nut.

This article written by Gerry Hayes and first published at