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Sep 10, 2020 - 7:38:38 AM
2625 posts since 10/13/2011

Hiya: I have a bone 5th string pip. It was installed a year ago (original pip cracked). Just figured out there is a "burr" in the slot, the string is catching. I'd like to try fixing this myself.

I am bewildered by the number of files available on the StewMac site. Is there a particular nut file size I should use to try to smooth this out? When the file(s) arrive, do I file the slot so it is straight at the bottom, or does it need to be angled slightly and if so in what direction?

Thanks for your assistance!

Sep 10, 2020 - 7:50:29 AM
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448 posts since 2/6/2011

Those nut files are expensive. This could probably be fixed with a folded piece of sandpaper. Alternatively, a cheap DIY nut file can be made from a set of feeler gauges. You can use a small triangular file to cut "teeth" in the edge of the desired width gauge (~ 0.010 inches -depending on which 5th string you're using). I usually angle downward toward the tuning peg so that the leading edge of the groove toward the bridge is highest.

Sep 10, 2020 - 7:57:50 AM

2625 posts since 10/13/2011

That is a brilliant (and budget-friendly) idea, thanks, Pat!

Sep 10, 2020 - 7:58:41 AM



3173 posts since 2/20/2016

Any of the nut files from about .012" to .018" should work. Check other vendors such as Warmouth, Stew-mac is getting rather pricey.

I still use a jeweler's "round edge joint file," made by Grobet and available at a jeweler's supply house. That's what we used before the luthier's suppliers started selling nut files. 0.6 mm will work. The slot should be angled so that it is slightly higher on the bridge side of the pip than the peg head side of the pip.

Someone will suggest torch cleaners from the hardware store. They don't work very well.

Sep 10, 2020 - 8:20:08 AM

13353 posts since 10/30/2008

If you want to go REAL cheap get a used hacksaw blade and use a fine flat file to thin the toothed area down with a taper on each side like a knife blade. All by eye. I got by with one of these for YEARS, cut off short (about 4" or so) and kept in my banjo case string box. I have no idea what thickness it ended up, but it worked. One of the things you pay for with real nut files is the precision.

For a real nut file I'd use a width slightly larger than your string diameter, to prevent pinching.

Good luck. I was lucky, and was bequested a set of Stew-Mac files by my late banjo buddy.

Sep 10, 2020 - 8:42:28 AM

2625 posts since 10/13/2011

Thanks, Bob & Dick!

Sep 10, 2020 - 9:38:08 AM

Alex Z


3950 posts since 12/7/2006

"I am bewildered by the number of files available on the StewMac site. Is there a particular nut file size I should use to try to smooth this out? When the file(s) arrive, do I file the slot so it is straight at the bottom, or does it need to be angled slightly and if so in what direction?"

The right tool for the job is the .010 nut slotting file:

Since the burr is in the bottom, you only have to reach the bottom.  The next size up, .013, could be too wide (although it would be suitable for a new slot) and then it gets pinched on the way down before it hits the bottom of the slot.

Another way, for a small burr, is sandpaper.  600 grit, available at any hardware store.  Rip off a piece about 1 inch square, and fold it in half, and squash down the folded edge as much as possible so that it can fit in the slot.  (Folded, it may not fit in the slot, and then you go to the nut file). 

A few gentle swipes with either file or sandpaper should do the job.  Don't need downward pressure.  The slot should be slightly angled toward the 5th string peg, so try that first.  However, to get rid of the burr without deepening the slot, might have to go straight through a couple of times.

If the sandpaper doesn't fit or doesn't work, then it's the nut file.  Again, a few gentle swipes, and nothing will be hurt except the burr.

Hope this helps.

Edited by - Alex Z on 09/10/2020 09:39:04

Sep 10, 2020 - 10:39:19 AM
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3173 posts since 2/20/2016

Make the slot at least .012" to avoid binding.
An important rule of mechanical engineering: a 1/2" rod won't fit into a 1/2" hole.

Sep 10, 2020 - 11:29:02 AM

Alex Z


3950 posts since 12/7/2006

Agree .012 would be good for a new slot.  Not making a new slot or deepening the existing slot.  The string fits fine already, and there is no complaint about string height.  Only a little rough spot at the bottom.  We don't know how wide wide the slot is now.  Just need something to smooth out the bottom.

So the question is, if you buy one file, is it the .010 or the .013?  If buying two files, then there are options.  If the .013 fits in the existing slot, then of course that's the one to use.  If it doesn't fit, then the .010 is at the ready.

Also, if smoothing out the bottom of a slot that is a little wider than the file, can rock the file from side to side.

Now, if the nut is to be deepened, then certainly would want to use a little wider than the string, and that's where the .013 comes in.

I'd go with the 600 grit or higher sandpaper first.  Could be a 90 second job.  smiley

Sep 10, 2020 - 2:18:23 PM

448 posts since 2/6/2011

What's the gauge on your 5th string? If you're using an 8 or a 9, I don't think you want to widen up to .013 or even .012 inches.

Sep 10, 2020 - 2:23:23 PM

2625 posts since 10/13/2011

Hi there -- I use 10 gauge strings for 1st & 5th. Will go to hardware store tomorrow for a piece of sandpaper, and see if that will do the trick. Thanks everyone!

Sep 10, 2020 - 3:01:24 PM

4521 posts since 11/20/2004

Not exactly abrasive, but sometimes pulling dental floss through the slot several times will help eliminate string binding. I would try it first due to the simplicity and ease.

Oct 24, 2020 - 6:46:49 PM
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2625 posts since 10/13/2011

Hiya -- I finally got around to getting the right sandpaper, and it did the trick. Thanks so much for that advice, nice to have that 5th string come back to life!

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