Drum Dials are terrific tools to use to make sure that your timpani head has even tension all the way around at each tuning lug. Having equal tension makes it easier to clear the head and to make the drum sound in tune with itself.
Using a Drum Dial can be confusing at times because when you tighten on lug it has an effect on the other lugs around the drum.
Here is a good way I’ve found to make the use of the drum dial less confusing.
Take a reading of what the Drum Dial says at each tuning lug by placing the Drum Dial two inches from the rim directly in front of the lug making note of which lug has the highest reading.
Place the Drum Dial at the opposite lug from where you found the highest point. If the opposite lug spot is lower turn the tuning lug a ½ turn; lift the Drum Dial from the head and then set it back down where it was. You will see a new reading. If it is still low give the lug another ½ turn and check it again by lifting and replacing the Drum Dial to the same spot on the head.
Don’t turn the lug any more than one turn even if it is still lower than your high point lug because you will find that by bringing up the tension on the other low lugs on the drum this lug will change.
Now move to another lug and repeat the process of comparing the head tension with the highest reading never turning a lug more than one revolution. Once you have looked at the tension readings of all the lugs and have made adjustments go around again and tighten the low lugs you find. You should be able to turn the low lugs up to the high mark on your Drum Dial pretty easily now