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Checking the diameter and roundness of a golf ball with the GBMD (Golf Ball Measurement Device)

Ensure a temperature of about 70° F during your measurements! 




1. Calibrating and Diameter Quickcheck

- turn adjust nut counterclockwise until the lower end
- put the calibration device into the GBMD
- turn adjust nut until the lower end of calibration device (Bild 3)
- put golf ball into device and try turning the ball (Bild 4)
- ball may not be turnable = okay




2. Determination of the diameter

- Put golf ball into housing (Bild 5)
- turn adjust nut clockwise by a quarter turn each time
- check if ball is turnable after each shift
- count and remember the amount of shifts
- if ball is turnable into one direction = value of T1
- put value T1 into diagramm and determine diameter 

the example in right sheet shows 1 1/4 turns (= 6 Shifts) 42,74 mm
= medium quality = grade B


3.Determination of the roundness

- turn adjust nut further 1/4 turn (=1 shift)  
- check if ball is turnable after each shift
- count and remember amoutn of shifts
- if ball turnabel into all directions = value T2
- roundness is determined by difference T1 to T2

1 shift = good quality of roundness
2 shifts = medium quality of roundness
more than 2 shifts = bad quality roundness

the example on right sheet ball no 1  shows roundness = 2 shifts
more than T1 = medium quality roundness 



4. Comparation of golf balls

- keep position of adjust nut as in measurement before
- put each ball one after the other into device
- check if all ball ar tunable easily
- if turnable in only one direction = diameter is bigger 
- if not turnable at all = diameter is bigger and/or roundness is worse



5. Set marker line

- turn adjust nut clockwise fully into the frame
- put ball into device
- hold ball from top and set marker line as shonw in picture