Soldered a zip pull back on, is that a done thing?

I did the same thing to a ski jacket pull about five winters ago, blobbed solder on the little metal loop and figured it woud last a season at most. Still there. The trick with a zipper pull is that it doesn't acutally flex much once it's attached, it just hangs there while the slider does all the moving, so a soft solder joint survives fine on that kind of thing. Where solder lets you down is on anything that gets bent back and forth, like a frame tab or a bracket, and a coat pull isn't that.

The chunky lump catching on the coil would bug me more than the strength question. I'd file it while you can still get at it, becuase every pass of the slider over a rough edge wears a little off both parts, and eventually you'll have a chewed-up slider. A few seconds with a needle file or even a fingernail emery board does the job, no need to redo the joint. I left mine slightly domed and smooth rather than flat, which gives the cord a shoulder to sit against without snagging. Brazing would be overkill and you'd risk cooking the nylon or the slider's plating doing it on a garment. If the joint ever does let go in the cold, a ten-second reflow with a pencil iron fixes it, so I wouldn't lose sleep over it. Let it ride, just dress the blob down.

Honestly I would have skipped the solder entirely and gone with wire. I had the same failure on a winter coat about three years back and instead of touching a torch to it I threaded a short length of thin stainless safety wire through where the tab used to sit, twisted the cord loop on, and snipped the ends. Never looked at it since. It flexes with the pull, it doesn't care about cold, and if it ever works loose I can re-twist it in ten seconds with pliers in my pocket. The other thing about a solder blob on a garment is the heat itself. That little stamped tab is usually zinc alloy or thin brass, and getting it hot enough to flow solder can soften the metal around the join even if the joint looks fine. I ruined a slider once doing exactly this on a tent zip, the pull ended up bending every time I tugged it because the tab had gone half mushy. On the filing question, a smooth blob will catch less on the coil but it also gives the cord nothing to bite into, so I'd say rough is actually fine as long as the lump isn't big enough to snag. If it does snag in daily use, a file and a bit of wet cloth as a heat shield while you touch it up won't hurt. For brazing on a parka, way overkill. You'd need way more heat than a garment tab can take.

Same conclusion here, solder holds up fine on a pull. Mine was on a work jacket, blobbed it on about four years back and it's never cracked, even thru a wash cycle somehow. One thing I'd add, after filing mine down I hit it with a tiny dab of clear nail polish over the joint. Keeps the exposed solder from going dull and scaly looking on the outside of the coat, and it stops any rough spots from catching the fabric either. Cord still grips fine through it.

I fixed a broken pull on my kid's snowsuit the same way last winter, except I squished the blob flat with the side of a screwdriver tip while it was still hot, then it barely needed any filing. Worked a treat. One thing I noticed though, my first attempt had a hollow spot in the middle because I rushed it and the iron wasn't hot enough, and it snapped within a week. Second go I let the joint heat up properly and fed in enough solder so it soaked right through. If yours is solid all the way through you're laughing, but give it a firm twist with your fingers before you trust it.

Update: went back in with the iron and pressed the blob flat using a screwdriver shaft while it was still molten, like the snowsuit fix above. Way less snag on the coil now, and a dab of clear polish over the top. Question though, someone said the pull barely flexes once it's on, but mine twists when I yank the zip at odd angles. Does that change anything?