Long-Winded...
The taper and profile have a great deal to do with how well a shaft transfers power too. If you like your twelve and a half mm playing cue you might consider the same size tip on your break cue, a little faster taper in the "pro section" and a parabolic arc near the joint to give it a little more spine.
Decreasing the tip's radius effects the size of the sweet spot. If you rarely use much spin on break shots you might consider a quarter radius instead of a nickel or dime. I strongly recommend a nickel radius or larger, bigger sweet spot and a better transfer of force than a dime radius tip.
Hu
Great advice, and I was going to mention this exact thing.
You mentioned you liked the breaking characteristics of the house cue with a small tip. The key there is that it does not have a pro taper on it! Snooker cues run ~10mm and are very stiff, because they almost exclusively run with a straight taper (or variation of).
i once used a house cue and it was a 12 and i was shattering the balls
Based on your experience, I would run the break tip 1/4-1/2mm above your playing cue. You won't notice it, and it allows room for grooming later, since the tip will be getting very mushroomed over time I'm sure.
...as for people saying about getting a super heavy break cue, that is a myth, because a break needs speed, and with too heavy a cue, the speed would be reduced. A thicker shaft also doesn't warp as easy. Chino
I agree totally with the weight issue. Get it as light as possible. The energy transfer formulas favor speed over mass. A slight increase in speed has a marked increase in energy, whereas a large increase in mass at the same speed has a small increase in energy transfer. (see Burne's [sp] second book- he explains it well) Plus, you normally cannot stroke the heavier cue with the same
control as the lighter one, so accuracy suffers. We all know a solid (accurate) hit on the pack at low speed is far more effective that a fast-as-hell speed that glances off the head ball (and often into the corner...)
If you think you have better control with a smaller size, then that's what you should use.
Excellent advice. One of the main reasons we use our own cue at all is in great part psychological. If you KNOW it is better, it will be better. Get it?
As far as strength, unless you go extremely small it doesn't matter. The builder should know when the ferrule thickness is to thin to use as a break cue.
And why it is important to work with a builder who will work with you. I think you have that, now just find out if he will do a straight taper for you!
As far as action on the c/b. You don't want any, unless you do. That is controlled buy where you hit the c/b, not shaft size. As I led to earlier, if you like a smaller shaft, then you will be more accurate with that size. Use what you like, not what others think.
Rod
Yes! If you have a 'whippy' shaft, a slight mis-hit can make the unintended english too great. If the shaft is stiffer, this is lessened; HOWEVER, if you don't hit with ACCURACY it doesn't matter! The best cue in the world played poorly, will give poor results. This points back to weight as well- if you can stroke that heavier cue fast and accurately, great. But, you are not getting any REAL advantage from this; any advantage from a 'heavy' cue is psychological, which again, is not a bad thing.
In conclusion, I suggest 1/4-1/2mm over your playing cue diameter, with a straight taper on the shaft. Ferrule material up to the task and a very hard tip (compressed Triangle for example) and use a nickel radius as minimum; with a quarter radius an excellent idea (unless your accuracy is excellent).
That takes care of the equipment, now work on you! Get a good solid base, solid bridge, and PRACTICE BREAKING! It is not fun racking for an entire day, but you will be amazed how much good a full day of breaking will do for your game overall. You should be completely clam at the time of breaking. When I watch the players with really good strokes, that will stroke in what looks like a slow, soft manner and completely annihilate the rack. I strive for that myself- I used to "get my body" into the break, but that just made a mess (but more power transfer does happen). You loose the control.
BOTTOM LINE: regardless of anything else, you must hit the head ball accurately. Any advantage that works for you to get to that end is the right thing to do!