DIYer here, new to flooring, looking for advice on my hardwood flooring situation.
Current subfloor: 3/4 inch OSB, structurwood edge gold (4x8 foot sheets, T&G)Joist spacing: 16 inches on centerPlan: 3/4 inch red oak T&G, run perpendicular to joists. Will use 1/8 inch insulayment material for sound dampening, as this will be on the 2nd floor of home (above grade).
My research has shown that hardwood directly on top of this OSB is acceptable. I realize not the best. But acceptable. Especially since the OSB is sound condition (intact), no deflection, no movement. And making sure my hardwood is perpendicular to the joists. So moving beyond that area of debate..
My question is regards to type and length of fastener. I've read for installing oak on OSB, staples are preferred over cleats, as they have better holding power in OSB. Is this accurate?My next question is: should I be very concerned with blowout in OSB when choosing length of fastener (staple OR cleat)? Does blowout automatically mean loss of holding power leading to loose/squeeky boards in months/years? Measuring the depths of drive of fastener (from on top of tongue to bottom of OSB, at 45 degree angle) my measurements are:2 inch staple would extend 1/4 inch beyond bottom of OSB (= blowout)1-3/4 inch staple would EXACT depth of bottom of OSB (possible blowout??)1-1/2 inch staple would fall 1/4 inch short of bottom of OSB (likely no blowout, BUT is this enough holding power??)
I'm running in circles trying to figure this out, and delaying my project each time in doubt. I think the insulayment layer (adding 1/8 thickness) is leading me not to choose 1-1/2 inch staples, whereas without that thicker layer I would have! If anyone has any knowledge or opinion, I would appreciate your words of advice! (Aside from the debate of OSB vs plywood.) Thanks!

I use a 2 inch staple for all of my 3/4 flooring. If you are worried about holding power then add more staples than the recommended nailing schedule. Staples hold well enough in OSB. If you keep track of the floor joists you could aim for them and get extra hold in the joist. A staple every 8 inches will give you extra hold. A staple within 2 inches of each butt-joint on each board is good. Depending on the width of your flooring, you can also fasten the tongue end of each board.

Thanks for your feedback, Pete. Sounds like you speak from experience installing hardwood on OSB. I feel like I read enough places to avoid OSB blowout like the plague, due to using fasteners too long for the total material thickness. Blowout would lead to weak holding power throughout the floor. I see the argument for staples into OSB: stronger than cleats, into a more inferior subfloor compared to plywood. And I have read the strategy of marking joists and trying to hit those when possible. (Of course, if you choose a staple length that does not punch through, you won't have the opportunity to tag the joists for extra holding power anyways.) When it comes to cleats vs. staples, I wonder if one creates more blowout than the other? I know I'm overthinking it. Thanks for your reply!

The staple will have 2 penetrations and the cleat only one. The tip of the cleat is tapered so it may pop more fibers loose.
The staples usually have more of a plastic coating to keep them together and this is supposed to melt when the staple penetrates to add more friction to resist being pulled.