Shanking is the hardest fault to diagnose because it happens to good and bad golfers. It creeps into your game with the early signs hard to recognise. Basically the club is moving outside the arc on the downswing. Causes:
1. tenseness in the hands and fear of swinging the club. [top hand does not move smoothly to pronation].
2. club goes back too much on the inside and wrists do not"break".
3. weight coming forward during the downswing.
4. stance in relation to the ball, too close?
You need to check everything about your swing: grip, position at set-up, position at top of back-swing,and
particularly any movement during the down-swing that will cause the club head to move outside the correct arc putting the hosel into the ball instead of the centre of the blade.
If this is a general fault with all irons your swing could be the main problem. If it occurs mainly with short iron chip shots look at your stance and hand action through the ball.
Hope this helps 
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