3. The differences process – shaping by reading off of templates.

When hitting a golf ball with a golf club, the golfer contacts the ground with the club head in such a way that a contact zone of varying width arises on the sole of the club head. The centre of this contact zone in the direction of the hit is referred to as the contact line. Ideally, the contact line runs exactly through the centre of the sole and therefore precisely central to the groves on the impact surface. In this case, the club could be accepted as individual fitting for the golfer in question. This would certainly be both lucky and coincidental. (Fig.13+16)

In general, however, the contact line is not on the centre of the sole. If the club is too short for the golfer (Fig. 14) or the lie angle too small, then the contact zone will be on the front part of the sole, towards the point. If the club is too long (Fig. 15) or the lie angle to great, then the contact zone will be located between the ideal centre of the sole and the hosel. In these two latter cases, the club then does not fit the golfer being tested.

Fig. 13 Fig. 14 Fig. 15

Nonetheless, adapting the golf clubs to the golfer’s body size simply by altering the lie angle would be extremely dubious. Ultimately, it would mean that some kids might play with clubs for which the shaft lengths would actually fit their fathers! The use of lie angle adjustments for fitting clubs should therefore only be used to a very limited extent. The head manufacturer’s specifications on possible useful bending tolerance must also be observed. In any case, the aim should be to use golf club lengths that are directly proportional to the WIM values of the respective golfer.

Using a dynamic lie test, we can determine the exact difference between the contact line of the golfer being tested and the ideal central contact line on the sole of the test club. This difference will bring us to the correct individual golf club lengths – providing the test club corresponds exactly to the golf clubs in the set to be produced: same shaft, same head, same lie. According to the dynamic lie test laid on the sole, the correct club size can be read off from the test club template.

Contact line as per dynamic lie test ...           and with template laid on.

The template is produced according to the measured values generated with a measuring club. The respective measuring club consists of the club head (of which the lie and loft angles are meticulously checked and adjusted) and a very stiff steel shaft (on which the length of the test club is marked in felt pen (Fig. 17)). The test club can also be used as a measuring club, provided the shaft does not bend during the measuring process and cause the result to be read incorrectly.

So, the measuring club is fixed in the measuring device, with the contact line lying directly in the centre of the sole (Fig. 16) and a plumb beaming on the impact surface contact area, perpendicular to a level on which the shaft centre line is aligned. Measurement is then effected with one 135 my strength red slide, which is pushed to the right and left perpendicular to the contact zone. A millimetre slide fixed to the impact surface facilitates accurate reading of the values (Fig. 16).

Fig. 16 Fig. 17

The two measured values of the ideal central contact zone must be equal, if the measuring club is fixed correctly.

Fig.18: how TWGT 550c Iron 3 sole differences arise.

Table: Measuring - Result - TWGT 550c Iron 3

The measuring procedure is repeated each time the position of the fixed shaft is changed by the height of the length marks by 0.5 inches vertically, either upwards or downwards (Fig. 17). The measurements are then entered in the “Measuring - Result TWGT 550c Iron 3” table, giving the exact differences on the sole of the golf club head (Fig. 18).

Transfer of the measured values onto a template, which must be an exact two-dimensional representation of the sole, gives an illustration of the possible contact lines which, in turn, fit the club sizes indicated (Fig. 19).   

Fig. 19: Template TWGT 550c Iron 3 (Fig. 100%)

This template can then be used for all test clubs with the same club head and the same lie and loft angles. Shaft, shaft flex, tip trim and grip strength must then be adjusted to the golfer being tested.

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