E strings keep breaking

[HogTime]

A month ago I restrung my homebrew F5 for the first time. Two E strings broke. Got some extras and they went on OK. Tonight an E string broke when I pressed down slightly on the part between the nut and post. Thought it was was binding at the nut. Put on another one and it broke just as I was approaching proper pitch.

They are breaking at the post. Both of them tonight had a perfectly straight section of wire at the end of the long remaining piece. I'm thinking maybe the edge of the post hole is sharp or has a burr. Strings are D'Addario steel 0.010. Both tonight were on same post. Not sure about the ones a month ago.

What are the expert opinions?

Would like to fix it so I don't need to buy E strings by the gross.

Thanks,

[Folkmusician.com]

If the strings consistently break at the post it could be binding at the nut, but suspect a sharp edge at the post. Give it a good filing, sanding.

[Frank Ford]

I vote for binding at the nut - soft nut material, too tight a groove, that kind of thing. Never ran into a tuning post that broke strings myself. . .

[Frank Ford]

I vote for binding at the nut - soft nut material, too tight a groove, that kind of thing - or stringing technique (kinking etc.).

Don't recall encountering a tuning post that broke strings myself. . .

[Frank Ford]

duplicate post.

[Tom Haywood]

I don't recall seeing this addressed very often. Do you bring your E strings up to pitch 1st or last? I see a lot of guitar players bring the lighter strings up first. Doesn't seem to matter much on the guitar, but it is asking a lot for those strings to hold all the pressure on a mandolin. Any little imperfections on the parts touching the strings or on the winding get magnified.

[buchrob]

Use a short length of scrap wound string as a flexible file and run it thru the post hole. If it feels like it's binding, you may have a small burr or sharp spot. Doing this for a minute or so should be enough to smooth out any string contact areas without damaging the plating.

[HogTime]

Thanks for the tips. At first I couldn't understand how binding at the nut would cause a string to break at the post (haven't had my coffee yet). Now I see that turning the post w/o the string moving in the nut would cause more tension in that short section than the fretboard section.

Since this is a homebrew instrument, the nut is not slotted ideally. I'll take a look at those slots and also run a wound string through the post hole, too.

Thanks,
Ralph

[Mandobart]

If they break right at the post, that can often be eliminated by how you wind your strings. Most people now poke the string through the post hole and start twisting. That puts the full tension right on the sharp bend the string has to make in the post hole. Over 30 years back when I started stringed instruments everyone I knew did the wrap first and then through the post hole method; that's how I learned. Wrap wound strings 3 times around the post and then go through the hole. Five times for unwound/plain strings. That way the tension in along the gentler radius of the post vs the sharp kink where it goes through the hole.