I can't be more official because it's the skill that everyone (should!) admire. True master of One-Arm Chin-Up possesses such biceps and lats (for their bodyweight, of course) that all conventional bodybuilders will silently stand in the corner, cry and burn from envy. He obtains arm strength to match that size.
Some people think that this feat of strength is out of reach. Especially overweight people. But it isn't so. I heard of at least two persons that are approx. 100 kg (220 lbs). I don't remember the name of the first one but the second is Metin a.k.a. LittleBeastM. You have probably heard of him. If not then here's link to his YouTube channel: LittleBeastM's YouTube Channel. You should definitely check this guy out. He's probably the heaviest guy to perform such feats of bodyweight strength.
Anyway, let's get back to tips.
Train with Singles
It may sound obvious but it took some time to understand this. Don't waste your time and energy on reps. Train with singles. It's the fastest way. In my experience training with single-rep sets is the fastest way to gain strength. It's even more true for One-Arm Chin-Up. You're traning for skill at first place, not for multiple reps in a skill. And it's difficult skill, believe me. You will spend much more time on easier progression steps if you will strive for 3-5 reps than if you will strive for a single rep. And what's the point? If your goal is to learn One-Arm Chin-Up you need to progress as fast as possible or you will spend whole eternity learning it.
One of the best ways to implement singles is Rest-Pause Training. Let me explain you. Pick progression step that is fairly hard but you can do at least one-two perfect reps. Perform single rep with right arm. Rest for 30 seconds. Then perform single rep with left arm. Rest for 30 seconds. And so on until you hit 5-6 singles per arm. Call it a day. Return 2-3 days later and repeat. It would take couple training sessions to hit 10 singles per arm. Then you have several options. You can either shave off 5 seconds of rest periods and work back up to 10 singles per arm or you can pick a bit harder variation and start over with 5-6 singles.
Pick Progression That Is The Most Effective for You
There are tons of progressions toward One-Arm Chin-Up. The most effective are considered rope or towel assisted, finger assisted and rock climbers'. Rope assisted is the best for me. I can always carry the rope in my bag. It feels the most natural. The main thing is that with rope assistance you can adjust intensity similarly to the barbell. Just count the fists on the rope and you're all set. It's very important for me. So you get it. Pick progression that suits you.
Don't Hit It Too Often
One-Arm Chin-Up is not that exercise that you want to overdo. Firstly, it doesn't progress that fast. Secondly, increased risk of injury. Once a week works awesome for me. You should experiment to find out how's best for you.
One-Arm Negatives and Static Hangs
In my experience One-Arm Chin-Up negatives are almost useless. They only teach you how to comedown from top hang. And that's all. They are good as introductory progression step but that's it. On the other hand, One-Arm Static Holds. In my opinion they are very useful. Bottom hang is useful for grip strength and endurance, 90 degree hang is useful for strength and moving past sticking point, and top hang is generally useful in One-Arm Chin-Up practice. Practice them but don't overdo.
That's it. I hope it will help you in your quest for the One-Arm Chin-Up. Thanks for reading and don't forget to subscribe and like (: