Why is a 1/2-ball hit (30° cut angle) so useful?
Here’s an excellent videos Mike Page put together on half-ball hit “gems:”
and here’s a good summary article from Bob Jewett (BD, November, 2000). The “natural angle” effect associated with a half-ball hit is one of the most important principles in pool and billiards.
Gem #4 from the video is the basis of the 30° rule, which states that for a rolling CB, the carom angle is very close to 30° for all cut angles between 1/4-ball and 3/4-ball hits (not just a 1/2-ball hit). This gem is the single most important and useful principle in pool, especially when used in conjunction with the peace-sign technique:
Gem #4 is an interesting proposition demonstration with the carom shot from the foot rail. NV A.1 shows a similar “sure-thing” proposition. The following article also illustrates and discusses the shot in “The 30° rule: Part III – carom vs. cut” (BD, June, 2004).
Gem #2 is explained and illustrated in detail in “Draw Shot Primer – Part I: physics” (BD, January, 2006). The concept can also extended into the trisect draw-shot aiming system. This is also a very useful “gem.”
Many additional resources, with lots of illustrations, examples, and video links related to these principle, can be found here:
- 30° rule resource page (containing many additional resources and video demonstrations of how and when the rule is useful).
- collection of instructional articles on this topic:
- “The 90° rule: Part I – the basics” (BD, January, 2004).
- “The 90° rule: Part II – breakup and avoidance shots” (BD, February, 2004).
- “The 90° rule: Part III – carom and billiard shots” (BD, March, 2004).
- “90° and 30° rule review” (BD, July, 2004).
- “The 30° rule: Part I – the basics” (BD, April, 2004).
- “The 30° rule: Part II – examples” (BD, May, 2004).
- “The 30° rule: Part III – carom vs. cut” (BD, June, 2004).
- “90° and 30° Rule Follow-up – Part I” (BD, February, 2005).
- “90° and 30° Rule Follow-up – Part II: speed effects” (BD, March, 2005).
- “90° and 30° Rule Follow-up – Part III: inelasticity and friction effects” (BD, April, 2005).
- “90° and 30° Rule Follow-up – Part IV: sidespin effects” (BD, May, 2005).
- “90° and 30° Rule Follow-up – Part V: the final chapter” (BD, June, 2005).
- “Fundamentals – Part V: CB position control” (BD, January, 2009).
- “Fundamentals – Part VI: CB control examples” (BD, February, 2009).
- 30° rule and peace-sign technique one-page summary and the angle template.
The 1/2-ball hit is a common shot, especially in the game of 9-ball, where you need to move the CB around the table a lot. With a 1/2-ball hit, the CB easily be given enough speed to travel significant distance. The CB’s motion can also be killed fairly easily with a 1/2-ball hit. Also, sidespin is very effective off the cushions with a 1/2-ball hit. For thinner hits, the faster ball speed reduces the effect of the sidespin; and for fuller hits and the resulting slower speed of the CB, the spin doesn’t grab as well, especially on new cloth.
Dr. Dave keeps this site commercial free, with no ads. If you appreciate the free resources, please consider making a one-time or monthly donation to show your support: