Nut decisions...

I wouldn't change it if it's working fine. I'd just tape around it to protect the wood and clean it up.

If the bone was cracked, it would be coming apart. I think those are what are known in the machining bidniz as "apprentice marks," usually caused by careless or ham-fisted use of hand tools.

 

I would replace it, it will be good experience making a new one. The only material I use is cow bone, unbleached for vintage instruments or for a vintage look, bleached if it looks correct on a particular guitar. I have heard that bleached is more prone to having soft spots, its never been a problem. I usually buy blanks that are the correct thickness for a give guitar - usually 3/16 for gibson but possibly 1/4 but it is possible to cut bone with a band saw. I do the rough shaping on my belt sander.

I've posted a few examples of nut making on various build and setup threads - the big difference between Fenders and other guitars is the way you roll the top of the nut on the tuner side and angle the slots towards the posts. And, as you say, you can always put the old one back in.

 

If you are worried about the nut splitting along the cracks you could wick some thin CA into them. And I guess if the nut is functional there is no reason to replace it, I just know it would bother me and it only takes an hour or so to make a new one. It is also a great opportunity to change anything you don't like about the old one - offset from the edge, spacing, action.

 

Sanding bone on a belt sander smells like burning hair - it drives my wife crazy. And for what it is worth, my little bench top sander is one of the handiest tools I have - I'm just constantly taking parts to it for a little clean up.

 

"Apprentice marks" Nice. I like that.

 

+1 on wicking some CA glue into those cracks before you try major surgery!

 

Watch you fingers if you get a belt sander

 

Probably work just fine. Mine is a little Ryobi that I bought at Home Depot - it does have a disc sander which I don't use much. You can kind of see it on the desk next to the drill press.



I just find myself cutting something on the band saw and turning to the sander to give it a little final shape.

 

One of my common go-to tools in my shop is a hand vise. This tool is a teeny-tiny version of a blacksmith's post vise, but with a handle designed to...hold in the hand.

This tool came from patternmaking, when cast iron sand molds were made from hand-carved wooden bucks. The hand vise is also popular in jewelry and model making.

I have a few that are antiques and they work as well as the day they were made. Not only are they perfect for holding a nut blank when shaping it on a belt, they are supremely useful for holding any small part when polishing, shaping, clamping, etc. I use one at least once a week for for any job that requires holding a small part. If you're clamping a nut blank in one, fold a small piece of cardboard around the blank to pad it and protect it from the knurling on the tool's jaws.

If you need to clamp a tiny part in a bench vise, clamp the part in the hand vise and then secure the hand vise in the bench vise.

You can find old ones for a few dollars at any junk shop in the rusty tools crate. These older ones are made much better than modern ones. Here's one of mine, branded General:



There are different designs; pay attention to the max opening for the one you're considering, as well as how they're made, because some modern versions contain alignment bars that get in the way. That's why I prefer the older design. You can get hand vises from many tool suppliers, as well as Amazon:

https://www.amazon.com/dp/B084V6N8HF/?tag=tdpri-20

and

https://www.amazon.com/dp/B0874V45T5/?tag=tdpri-20

and

https://www.amazon.com/dp/B07KTLTPHL/?tag=tdpri-20

 

Hmmm I'm no osteopath, but translucency in bone leads me to believe there's more air in there. Do you have a small scale that measures grains or grams? If they both ring when dropped on a hard surface, choose the heaviest one.

 

Which bench top sander do you use? I am getting tired of building nuts completely by hand with files and sandpaper..

 

I've done sort of a hybrid of some of the above: vise grips (sometimes padded) and a bench grinder.
You'll get the same burnt hair smells as Freeman mentions above, but luckily, I've had no problem with burn marks or the like. Smells bad, but works fine. I be sure to mark it up good and work under good light so I know EXACTLY when to stop grinding on it. After that, I give it the fine sandpaper followed by a good polish.

Edit: Gloves and eye protection are definitely recommended!