The tale of the accursed spoke
 

Last Friday some jerks, angry that no one would let them into the Round-the-Clock Gym without paying, smashed its Ring camera and bent the rear wheel of my bicycle.
LBS had 32-spoke rims only so I had to buy on-line.
I built the wheel with only 1 mistake (not lacing a spoke under the last it crossed.) I usually make a few and more serious.
I had it dished and nearly trued when I rounded the sides of a nipple. I took the bad nipple off with lineman pliers (Locking wrenches destroy the nipple before they get it off.), tried another, had the same outcome.
I had used a 302mm when I should have used a 301 - carelessness.
Then the same happened with a new spoke and nipple: the spoke wrench, a Spokey (what Sheldon Brown recommends 2nd), that I had used for 30 years had finally worn out. Fortunately I have a little-used Park to finish the job with. Never broke a spoke wrench before.

The very first thing I do BEFORE building ANY wheel is thread a spoke and nipple together to see how much allowance for overrun I have. While spoke thread length is fairly consistent brand to brand, nipple thread length, or more specifically the thread relief depth at the hub end, varies greatly brand to brand.

As I read your post, my first reaction was that you ran out of thread and jammed the threads. If so, let's hope that spokes are measured correctly and that you will have enough overrun room if needed.

BTW- for anyone reading this and having similar issues, I (only when I have to) use a 2.1mm reamer in a drill clamped in a vise, and finger feed nipples to add 2-3mm of thread relief. It takes a bit of touch, so you might want to improvise a depth gauge of some kind. If you have a drill press, fixture a spoke with about 1-2mm of thread showing as a support, and the job goes very fast, without needing strong fingers.

You know what you are doing. I re-used the spokes and nipples from the vandalized wheel, which I had built in 2014 with the spokes and nipples from its predecessor, re-used from its predecessor, with occasional replacements from my collection of salvaged spokes and nipples. How I got away with a 302 in the previous wheels - I don't know. Of course I should be using shorter spokes rather than ones that stick through and are nearly too long - but I don't have enough of those, would have to make a purchase gasp!. In other words you know what you are doing and do it correctly. Do what he does kids, not what I do. I posted this message as a warning.

That was my second reaction, after I broke the second spoke. My third reaction, after I posted this message, was that I put too much tension on the spokes. I use only a wrench and a hand-made dish tool, no truing stand or tensiometer. Usually I build a wheel with too loose spokes, tighten them up gradually over a few days; once I pulled a nipple through a rim (no eyelets, a cheap, thin Araya), an exciting moment (made a sharp, loud sound, ruined the rim). So far this one has ridden well, and silently.

I don't understand what you're describing - you ream the tops of nipples so spokes can insert further?

This is one of the very few issues that I find myself in disagreement with you. I obviously don’t have your long history in wheel building having come to the craft relatively late in life, but the volume of wheels I have built and repaired in the last decade is pretty huge.
Much of what I have learned has been from wheels that come to me for repair. Many of these wheels showed signs of previous repair most notably spoke replacements.
I would frequently find someone had used a spoke that was much too long with a ridiculous amount protruding from the nipple.Obviously this means the nipple thread had been overrun by a significant amount. More often than not that replacement spoke would not be the issue that brought the wheel to me.
These experiences led me to believe that going a few turns beyond where the nipple runs out of thread is not really a problem.
I still shoot for ideal spoke length but these days I tend to round up rather than down.
This guy supports my contention. https://wheelfanatyk.com/blogs/blog/nipple-threads

There's room for disagreement here. So two points:

1- free room for spokes to overrun nipple heads varies greatly. Some, especially lower cost, spokes often have more thread length, and some nipples have less than average, so overrun can easily be 1/4" or more.
2- While The brass is soft, and that amount of distortion involved isn't great, it can still cause rounded nipple flats on tight wheels. As it is, even under ideal conditions people already have problems rounding nipple flats as spokes reach tension limits, as in the case of right side dished wheels. The added torque from crushing threads can easily make the difference between a potential issue and an actual one. Also, for those who, like me, use thinner or butted spokes the added torque increases spoke twist, adding one more thing to deal with.

But nobody has to choose between opinions here. I invite those who care to take any nipple and run it down on any spoke past the limit and feel for themselves how much torque is involved. Then thay can factor that into their spoke length planning.

BTW- like you I work my spoke length tolerances erring high rather than low on hollow rims, but I reverse that thinking with single wall rims, to avoid having to file any protrusion.

"Tops" is problematic here. So to clarify, I ream the nipple opposite the head to shorten thread engagement and allow more free overrun. FWIW the only thread engagement that matters is close to and within the head. The longer thread engagement is a convenience to builders since it makes lacing easier.