nut slot burnishing

[Dick Hutchings]

I use the Stew Mac nut files and the slots don't seem to be as rounded or smooth as I would like. I'm considering making a set of burnishers from feeler gauges. Has anyone else found issues with these files and if so, how do you finish the slot?

[Lefty Luthier]

I agree that the Stew Mac files do not give a smooth surface. I use a set of torch tip cleaners to add smoothness. Low cost and works fine.

[Dick Hutchings]

I'll see if I can find some. Thanks.

[sunburst]

I string 'em up, and by the time they're in tune, the strings have burnished the slots.

[strings777]

I use 1000 grit sandpaper to polish the slots after cutting them with the Stew Mac nut files.

[Paul Hostetter]

I string 'em up, and by the time they're in tune, the strings have burnished the slots.

Bingo. There's a whole thread going on now about this that and the other thing about lubricating and so on. I find it all (after 40-some years in the biz and many thousands of nuts) to be utterly unnecessary. Cut and dress the slot right, the strings themselves take care of it in no time.

I did hear someone once say they'd installed lengths of strings in a selection of jeweler's saw frames, and used them to burnish the slots. Seemed a little over the top to me.

I use a mouse-tail file from Shar (made by Grobet) for final dressing for wound strings, and a three-square #1 cut jeweler's file for the unwound ones. I never found much use for the commercial nut files.

I also can't see how 1000-grit paper can be used in a slot either. A string itself is so much better suited.

[Rob Grant]

I'm the joker that uses the jeweler's saw, but not to polish or burnish. My selection of files is somewhat limited, so I cut as close as I can with what's available. I then "size" the slot with a short bit of the string that will be used in the slot installed into a jeweler's saw frame. This technique is really only useful with the wound strings. In one case, I actually smeared a bit of valve grinding compound (ex-diesel fitter<g>) on a wound string to open up a nut slot on a mandola... works a treat!

[Dick Hutchings]

I have the "special nut files" and I haven't made a smooth working slot yet. The worst is the A slots where I use a .016" file for a .015" string. The next size up would be a .024". Yesterday I chased the slots with a 3 corner jewelers file and that solved the problem. Why did I buy the files?

[mandotim1955]

Another vote for the welding torch tip cleaner files. They come as a set in different diameters, get them from a good tool store. Cheap and effective.
Tim

[sunburst]

Dick, I've checked the actual cut of some of my nut files and re-labeled them because they do not cut slots the size they said. I have one that came labeled .017" and the slot turned out to be .015". Maybe your .016" file is not cutting a .016" slot.

[Dick Hutchings]

I'm pretty sure it isn't. I measured them when I got them quite a few years ago, just so I could put an arrow pointing to the correct edge of the double file. I should measure it again with this in mind. Either way, I need to replace it with a larger file or chase it with a triangle as I did again this morning to another problem nut. The strings slip almost perfect now. I can still detect a slight increase with a tuner, maybe .5 cents at most change when I stretch the string after I tune. I think there will always be some tiny amount of resistance that will have to be overcome. Can you really get it perfect?

Dick, I've checked the actual cut of some of my nut files and re-labeled them because they do not cut slots the size they said. I have one that came labeled .017" and the slot turned out to be .015". Maybe your .016" file is not cutting a .016" slot.

[pops1]

I have had my stu mac files for over 20 years and they are not as sharp as they used to be so the cut a smoother slot these days. Using less pressure takes longer, but will help smooth out. Especially at the last use very light strokes.

[Cathal Whelehan]

I'm not sure if this addresses the OP's issue of rough nut slots, but a tip I once was given to ensure string moves smoothly through the slot while tuning etc. was to simply sharpen a softish grade pencil really sharp and score it back and forth in the slot to 'lubricate' it (re-sharpening for each slot). Admittedly, I don't know if this alone is enough to even out tiny bumps and cavities.

[Dick Hutchings]

I probably just used the wrong terminology. What I really want is a rounded bottom which I don't think I'm getting with these files. I think I'll take a nut that I've slotted to work with me and put it under the microscope and take some pictures. That should answer that part. I may also be leaving too much material above the string though I strive for half the diameter of the string. I probably don't get it perfect on the smaller strings. Seems like that shouldn't matter because the top half of the string is rounded away from the sides of the slot anyway.

I've figured out how to make the slots work better using a triangle file but it seems like I should be done after the SM files.

[Paul Hostetter]

I find a good 3-square (triangle) jeweler's file, skillfully wielded, will do a plain string slot beautifully. I don't think pencil lead does anything except make a bit of a smudge. I think even a plain string will burnish and finish a fresh slot well, and in no time. Get a good loupe and have a good close look at some nut slots you know work well.

We've probably all experienced strings that sizzle on the first fret. These are almost always ones that were set in an initial setup to a perfect clearance, and later worked their way down that last 10th of a millimeter through actual use.

[Mike Bromley]

I string 'em up, and by the time they're in tune, the strings have burnished the slots.

I've successfully burnished them by reciprocating a string back and forth through the slot.