The usga face roughness rule is based on a thing called “Roughness Average”. RA, in the best way possible, is a complex formula that takes into account the “texture” of a surface and the overall “waviness” of the surface, then averages that out. The USGA rule is 180 RA. This is equal to the raw surface created by a typical forging process or a very good casting process of metal. Pretty logical choice for our sport. The results are “decorative” areas on the face of irons that are now pretty smooth compared to years past when we had those grinder wedge faces, which made the rule change, btw.

As for grooves, well those equally spaced cuts on my ball with those shaggy bits of cover material hanging from them aren’t from nasty birds attacking my ball in their territory.

The real answer is a little bit of both. Golfballs only “see” mass and acceleration. You can make them go with a rock tied to a stick. As for putting some spin to it, well, certainly, there is frictional rotation applied but far less these days than before the USGA face roughness rule changed. Then there are those little slits in the ball cover after contact to account for. Oh, Golfsmith did some testing years ago and grass in your grooves makes a 5 to 15 yard loss of distance due to reduction in spin. That’s aerodynamic lift reducion due to loss of backspin from clogged grooves and that was with V grooved 8 irons!

Go figure which is the most important of the TWO aspects of spin.

However, it’s probably not really something to get too concerned about, unless you’re a professional or play competitive amateur events. The USGA isn’t going to adopt the groove rule in most of its championships until like 2014 and recreational players won’t have to think about it until 2024.

While I agree with your points on Pelz, I must say that as I’ve been digging through the references that Rookie provided, I’m intrigued by what I’m seeing. Specifically, I was led to The Search for the Perfect Swing, which I’m currently reading.

It’s a summary of a scientific research project (targeted at the layman) conducted in the late 1960′s. There’s a section in there that discusses spin. They do support the points Rookie made, and to me the most interesting fact they point out is that the club meets the ball with something like a couple thousand pounds of force (that’s a ball park figure as I can’t recall the exact number). Stated a different way, that’s like saying that from the point of view of the clubhead, the ball weighs like 2000 pounds.

The point they make is that with that much force between the club head and ball, that any gripping power that the grooves provide is almost irrelevant to the production of spin. It’s kind of like dumping a bucket of water in the ocean and taking credit for helping to flood some island somewhere.

They ran tests with irons with completely smooth faces versus irons with normally grooved faces and found that the production of spin was almost the same. I believe the grooved clubs put an ever so slightly greater amount of spin, but it was a small enough difference as to be virtually negligible.

FYI, Dave Pelz has a college degree in Physics and he worked for NASA
before he became a PGA Teaching Professional. I think a guy with that much education and experience along with being a lifetime golfer knows what puts backspin on a golfball.

Simply put, hard steel clubface with a sharp groove edge and/or milled face will dig into a soft cover ball more and provide more backspin than a smooth clubface and/or smooth groove edges, guaranteed. This assumes a decent swing speed, more speed equals more backspin, guaranteed. This is fundamental physics, guaranteed.

While you may not have liked Dave Pelz personality, he may have found your ignorance of basic scientific principles annoying.