Re: New grip causing alot of blisters, reasonsWell, as been said grip pressure is probably the prime culprit here. I don't completely like thinking about a 5 on a scale of 1 to 10; if only because what one person thinks of 10 is different from another. I like Sam Snead's old quote about gripping it like you would a bird. Tight enough that the bird isn't going to get away but loose enough that you don't crush and kill the bird. But, that really is just a starting point, you need to find what works for you, though I wouldn't go too much tighter or looser from Snead's basis point.
Also, not just your starting grip pressure, but your grip pressure throughout the swing can affect this too. A lot of people grip down tighter on the transition from the backswing to the forward swing. It really should be the same all the way through. A nice drill is to swing back and forth, a little more than half way each way, and concentrating on keeping the exact same pressure you had when you started the entire way through. That is, if you started with a 5 (or a 4 or a 2.5), then when you swing back make sure you are still at 5 (or 4 or 2.5) and then on your way down make sure you are still at 5 (or ...) and then at the end once again make sure you are still at 5 (or ...). If the club is moving at the transition, and that's making you re tighten you grip at the top, that can definitely cause blisters.
Lastly, I want to explain a little why too tight is very bad for a golf swing. The muscles in your forearms and wrists tighten up when you grip something, and hence there is a loss of flexibility. You don't want to lose flexibility in your wrist cock, for example, because that is the source of generating lag in your swing which turns into power. In a book written by Cochran and Stobbs called Search for the Perfect Swing they measured how large the range of motion in the cocking-uncocking direction correlates with grip tightness. A maximum tight grip has a zero degree range, as you might expect. Three-quarters maximum has a 26 degree range, half maximum tightness has a 57 degree range, one-quarter maximum tightness has a 70 degree range, and no tightness at all had a 77 degree range. You can see how too tight can really disrupt the cocking of your wrists and rob you of power.
Ultimately, you'll probably learn how everything seems to work better in the golf swing if there is a looseness or a flow to the swing. It is a hard habit to overcome, but there is also some truth in the saying "give up control to gain control" That includes holding on to the grip really tight.