Hi everybody.
I am in need of help. I am planning to nail 3/4 unfinished solid Brazilian cherry and walnut 5 inch wide to 3/4 plywood on concrete grade level. I've tried different brands of 1 and ½ inch "L" cleats using Powernail 45R (manual ratcheting). All cleats were essentially the same (except for powercleats had rounded tip instead of the flat square, but that did not seem to make any difference) and all split the tongue with cracks running few inches to both sides of the nails. I‘ve tried driving the cleats only partially with the nailer and finishing it carefully by hand- same result, but noticed that driving long head of the cleat into the wood made crack significantly bigger. There is no complete separation of the tongue, but cracks are from 1 to 3 inches long and as wide as cleats are thick and there is some down displacement of the tongue. There was no over penetration of the cleat, misalignment or malfunction of any kind with the nailer. I've only tried it on few scrap boards, but have not started actual nailing of the floor. Please help me out:
-How common is it from your experience? How often do you see cracks in common woods and in hard brittle Brazilian?
-Will pneumatic do any better?
-Will staples do better?
-should I predrill and hand nail? With what type of nail?
-Any other method to install?
-What worked for you?
-Please share your experience with Brazilian wood, also tricks and tips.
Thank you,
Yuri

Typically, the harder the wood, the more chance of cracking and tongue split. Because I own a Bostitch M111FS, that is all I've used and it has worked fine. Occasionally, a staple will break or a tongue will crack. Some prefer to predrill and hand nail. Others feel the cleats break tongues less but you don't seem to be having much luck with them. I will say with 5" flooring, you may wish to consider gluing the floors down in addition to nailing.

Yes, That could be your whole problem.

Thank you guys,
Yuri

Glue is stronger than nails, if the glue we have today existed in the 1800's then T&G would never have been invented.

We have in some instances used bradnails, which frankly I like. Cheap, fast, easy. They hold the board until the glue sets.