How would you bevel the string hole of tuner post?

[Taylor Ham]

While doing a setup on a friend's old beater I had the strings tuned and detuned a couple times, breaking the e string at the sharp corner on the hole, and should probably get around to fixing it rather than putting so many wraps to get below the hole.

[nikpearson]

You can pick up diamond coated needle files cheaply and they are likely to give a smoother finish than standard files. One with a circular cross section will probably be the most useful. You could also try using a fine abrasive paper - 400 grit or more - wrapped around the same file or similar object.

Depending on where the sharp edge is you may be able to resolve the issue by sanding across the tuner post. You can get 3 or 4-way nail buffers which have very fine abrasive surfaces similar to micro-mesh. Start with the finest to avoid marking the post unnecessarily.

[Howard Emerson]

Originally Posted by Taylor Ham

While doing a setup on a friend's old beater I had the strings tuned and detuned a couple times, breaking the e string at the sharp corner on the hole, and should probably get around to fixing it rather than putting so many wraps to get below the hole.

Here's the perfect Dremel attachment, and you don't need to buy a Dremel tool to use it in a drill:

https://www.amazon.com/Dremel-463-Ru...8549784&sr=8-1

Regards,
Howard Emerson

[Alan Carruth]

Get a countersink. Most of the ones I've seen come with an odd number of cutting edges, so they'll make a clean cut, unlike a drill bit. Tuner posts are usually soft enough that you can just do the job by hand.

Alternatively you can file across the hole with a small round file. It's not as good as the countersink, though.

[Rudy4]

When I've had the occasional set of machines that had sharp edges at the string post holes I used a small fine cut round file across the hole followed by light sanding using a sandpaper wrapped 1/4" wood dowel.

Countersinks remove most of the material at the upper and lower edges of the hole which the string doesn't contact. It's a bit like using a chain saw for fine furniture construction. The only edge that matters is the small portion where the string contacts the hole edge, not the top or bottom edge of the hole.

A small conical stone, as shown earlier, can also be used judiciously to smooth that area without chewing up the top and bottom edges of the string post holes.

[Taylor Ham]

Originally Posted by Rudy4

When I've had the occasional set of machines that had sharp edges at the string post holes I used a small fine cut round file across the hole followed by light sanding using a sandpaper wrapped 1/4" wood dowel.



Countersinks remove most of the material at the upper and lower edges of the hole which the string doesn't contact. It's a bit like using a chain saw for fine furniture construction. The only edge that matters is the small portion where the string contacts the hole edge, not the top or bottom edge of the hole.



A small conical stone, as shown earlier, can also be used judiciously to smooth that area without chewing up the top and bottom edges of the string post holes.

makes sense that the sides of the hole matter more than the top and bottom. I've got some needle files that should do the job.

[canyongargon]

If you need to take off a light burr my first attempt would be with some abrasive cord flossed through the hole so as to hit the offending edges.

[GHalliday]

Mounted abrasives or staggered flute chatter free burr. Het a conical shape.

[Monsoon1]

I spent 20 years as a machinist, and the zero flute weldon countersinks made the smoothest edges.
For a tuning key post, you wouldn't even need a drill.
Just press it into the hole and twist with your fingers.

There are cheaper ones on amazon. Make sure the small size is small enough.

[Monsoon1]

They're known as zero flute countersinks.

https://www.amazon.com/Taytools-4672...206637&sr=8-12

[Alan Carruth]

In effect that's a single flute cutter. I've made single flute taper reamers by turning a taper on the drill press using a file or stone, and then filing away nearly half of the diameter to get a 'D' section. It works on a scraping cut, and will make a round hole in side grain wood for things like friction pegs or bridge pins. For wood you can get usable service out of an aluminum taper for a while, and since most tuner posts I've seen are brass you could probably get away with using mild steel to make a deburring cutter for those.

On wood pegs I usually do simply cross file the hole ends with a small round file, and they're fine. The strings can compress the material enough to avoid a too-sharp edge. With metal the slightly sharper than ninety degree angle can still be hard enough to cause the string to break there due to the sharp edge, so even with cross filing it's still a good idea to break the edge back. That can be done with a marking knife that has a short bevel, but I prefer a countersink.

[bnjp]

I use a round tapered needle file.