Lots of teachers will tell you to hit our irons with a descending blow. But what is a descending blow? To hit it with a descending blow, you need to hit the ball before the clubhead reaches its lowest point of the swing arc. You hit the ball first and then take a shallow divot. You don't want to hit down on the ball with a steep angle of approach into the ball. You want to take a shallow divot with a slight descending blow with all irons except for long irons. With long irons and hybrid club, you want to sweep the ball off the turf unless the ball is sitting down on the grass.
Why do you want to hit it with a descending blow?
There are feew reasons why you want to hit it on a descending blow.
1. Hitting the ball with a descending blow will create backspin on the ball
When you strike a ball with a descending blow, you will push the ball against the turf just before the clubhead takes the divot. This creates backspin on the ball. Shots with more backspin will go straighter and stops quickly on the ground.
2. It allows solid contact with the ball
Even if yur ball is on the fairway, it's not the same as the teed up ball. The ball may be sitting down a bit on the grass. When you try to sweep the ball which is sitting down a bit, you will catch the grass between the clubface and the ball. This will make it harder to hit it solid. To catch the ball clean, you need to avoid the grass behind the ball. That's why you want to hit it with a descending blow to make sure you catch the ball first.
Ball Position
to hit your middle irons and short irons, you want to pay attention to your ball position. Most amateurs put the ball too far forward in the stance.With short iorns, place the ball in the middle of the stance.With middle irons, put it little left of center. This will make it easier to hit it on the downswing blow.
Hands Position
At impact, your hands should beat the clubhead. In other words, you want your shaft to be leaning a bit toward the target.
Here is the drill to help you do just that.
1. Put the pen 4 inches behind the ball
2. Start hitting the ball. Make sure you avoid the pencil.
If you hit the open, you may be sweeping the ball or hitting well behind the ball. So make sure your hands are ahead of the ball at impact. Another good drill is to hit balls with a golf ball under your back foot. With this drill, don't swing hard at all. Swing with 50% of your swing speed. Make sure you hit the ball first and then the turf.
Check the Divot
After hitting the iron shot, check the divot because the divot will tell you lots of things about your swing. If it's pointing right of the target, you are swinging inside out. If it's pointing left of the target, you are coming over the top or cutting across the ball. Also, if the divot is deep, you are hitting down too much on the ball. When you hit down with a steep angle of approach, you lose consistency and also hit lots of slice and pull shots. To take a shallow divot, you need to swing from inside the target line. If you see deep divot after the shot, that's the sign that you are cutting across the ball. If you do this, you will hit it far with short irons but lose distance with middle irons or long irons.
Limit Your Follow Through
Here is the good drill taht will teach you how to hit it with a descending blow.
1. Using a 7-iron, swing back to the top and start down.
2. Hit the ball but try to limit your follow through
Try not to swing beyond your waist after impact. This is especially a good drill for players who are scooping the ball off the turf. If you try to scoop the ball, you probably won't be able to stop at your waist height. Another good drill is to stop at impact. You don't have to hit balls with this drill. Just swing back to the top, start down and stop at impact.
It's very hard to stop your clubhead at impact. You nedd a lot of power to do this. But it will help you hit your irons with a descending blow and gain more distance.
Reference: http://www.golfsamurai.net/fault-fix/hit-it-with-descending-blow.htm