Official Luthiers Forum!

I just replaced a set of strings on my friend's Ukulele.
Upon tuning it the high A bridge pin popped up (twice).
The plastic pin (slotted) is snug in the hole but obviously not tight enough.
Anybody know a quick and easy way to slightly enlarge the bridge pin hole?
Thanks.

The ball or knot (whatever is at the end of the string) should pull on the top not on the pin. Make sure the knot or ball is tight against the top when you put the pin in the hole. Enlarging the hole should only make things worst.

Thanks Alain,
I'll check the knot location when I reinstall the pin.
By the way, you are right on not enlarging the bridge pin hole.
I misspoke...I meant to ask if I could add glue/sawdust or something else to make the bridge pin hole slightly smaller so the pin would fit slightly tighter.

Pins that won't stay down are more likely because of a worn bridge plate or, if not present on this uke (not all ukes have bridge plates... some imports have neglected to use a bridge plate...) the pin hole in the top is worn permitting the string balls or knots to travel up the pin holes pushing the pins up as well.

One solution is a bridge plate cap or, if there is no bridge plate, a proper bridge plate cap glued to the bottom of the top. It's an opportunity to redrill the pin holes (3/16th") ream with a reamer matching the taper of the intended pins (usually 5 degrees but at times 3 degrees or even something different).

This also begs a discussion on the virtues of unslotted pins but I won't subject anyone to this here...

A typical bridge plate cap is approx. .060" thick, often hard maple, around 1/4" longer on both ends than the pin spacing and around 1/2" wide. It's glued directly to the underside of the plate or the top if this one has no plate. You can use the two outer pin holes and some 3/16" dowels to aid in positioning and then a caul that won't stick to the glue and clamps. It's pretty easy to do and is also used to extend the life on vintage instruments that had stinkin slotted pins that resulted in damage to the plate.

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Ann Arbor Guitars

When I install strings I like to lightly pull the string up as I'm putting the pin in. You can sometimes feel the ball getting caught on the pin so a little wiggling will help it come to rest against the bridge plate or top.

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Another day, another dollar.

Thanks, Alain, Hesh and Michael for the great input.
The problem seems to be solved.
When I first strung up the Uke, I was pushing the knot all the way down into the hole with the bridge pin.
So when I tightened the string...Pop...it came right back out.
Once I changed technique, poked the knot down into the hole and pulled it tight against the bridge plate...and then pushed the bridge pin in fully - Amazing!
No more flying bridge pins.

It's humbling to think that after so many years of pursuing this hobby...I've still got some nubie mistakes left in reserve.
Or...hopefully...that was the LAST one!
Thanks!