What is lie angle and how does it affect my shots?
Lie is the angle of the head in relation to the shaft. A proper angle will ensure that the score lines are parallel to the ground when contact is made with the ball. If the angle is too upright the ball will go left of the target, if too flat, it will go to the right. Lie can be checked and adjusted by Professional Clubmakers.
Why should I worry about the loft of my clubs?
Most “off the rack” clubs do not increment properly. That is, there is not a consistent number of yards difference from club to club. For example, a 7 iron may hit farther than a 6 iron. By checking and adjusting loft, a Professional Clubmaker can correct this problem.
What is Swing weight?
The swing weight is a measurement of the distribution of the weight of a club. A club with more of its mass concentrated in the club head has a higher swing weight and requires more energy for the golfer to swing it at a specific speed. Golfers should use clubs with the correct swing weight to maximize their potential.
Club makers measure swing weight with a special balance that positions the club at the correct fulcrum point and determines the amount of weight required to counterbalance the overhanging portion of the club. The balance may read directly in swing weight, or it may require a chart to convert its readings to swing weight.
Swing weights use a letter-and-number combination that represents the range and the specific reading. There are six ranges, from A through F, and each has 10 values, numbered 0 through 9. A0 is the lightest, and F9 is the heaviest. Most men’s clubs fall in the range of C9 to D8, with D2 being the standard, and ladies’ clubs are usually between C4 and D0. One point on the scale is equivalent to a weight difference of .07 oz. at the club head, about the weight of a penny. Few players would even notice such a small change.
Stronger players should use higher swing weights, and weaker ones require clubs with lower values. The correct swing weight is one that is light enough for the player to achieve enough club head speed for proper distance and ball flight but heavy enough to transfer sufficient energy to the ball and keep the club on track in the downswing.
Then what is MOI?
MOI or Moment of Inertia is a measurement of resistance to movement around an axis of rotation. In golf heads it refers to resistance to twisting caused by off-centre hits.
It’s application to a whole golf club refers to the amount of energy required to swing the club and is used in place of swing weight to provide a more accurate measurement for matching clubs to each other for consistent feel.
For a more detailed definition check out Tom Wishon’s explanation at his website