What differences does tip hardness make, and does it affect how much spin can be applied, or the amount of squirt that results?
Here are some relevant factors and effects related to tip hardness:
- A hard tip lasts longer and holds its shape better over time, in general.
- Tip hardness (within the typical range) should not have a direct effect on the amount of spin that can be applied (see more below).
- The amount of spin is limited by the tip offset that creates a miscue (see miscue limit).
- A soft tip will give the cue a softer “feel” (less impact in grip hand) and have a different sound than a hard tip. Some people prefer some sounds and “feels” more than others. For more info, see cue “hit,” “feel,” and “playability.”
- Tip hardness (in a typical range) has no practical effect on CB deflection (squirt), per the info below.
- Soft tips can become harder with use.
- A softer tip will leave bigger chalk marks on the CB, which can cause more-frequent cling/skid/kick (bad hits).
- The shorter a tip is cut (or worn down with use and shaping), the harder it will play.
- If a tip is not scuffed (either with a tool or with frequent chalking with a traditional abrasive chalk), it will not hold chalk very well, and miscues will be more likely. A harder tip might require more attention in this regard.
There is no question that a harder tip “feels” different and provides different “feedback” (a softer tip typically dampens the impact a little and the force of the hit isn’t felt as strongly). It is also true that a harder tip can result in a more efficient hit, providing more speed to the CB for a given cue speed. And it is true that with slower CB speed, more backspin will wear off on the way to the OB with a draw shot and more sidespin will wear off on the way to the cushion with a sidespin shot (especially on slow and sticky cloth with slower shot speed). These effects might make it seem like a softer tip is applying less spin to the CB. Regardless, the quality of spin (i.e., the spin-speed ratio) delivered to the CB depends only on the tip contact-point offset from center. The physics on this is very clear. If anybody doubts this, they should do a careful and objective experiment to compare any tips they think would produce different results. For those who have math and physics backgrounds and are interested, the physics showing how the spin-to-speed ratio depends only on tip offset from center, even when accounting for tip efficiency, can be found in TP A.30 – The effects of cue tip offset, cue weight, and cue speed on cue ball speed and spin.
Some people think that because a soft tip stays in contact with the CB slightly longer (see contact time), a soft tip can apply more spin. However, see Bob Jewett’s comments below. Also, the contact time is still extremely small with both a soft and hard tip: close to a thousandth of a second (0.001 s). Assuming the CB speed is the same in all comparisons, even though the peak force will be different (more with the shorter contact time), the amount of momentum (linear and angular) transferred to the CB will still be the same (because the sum of force over contact time is the same in both cases). The CB doesn’t move much (translation or spin) during the extremely small contact time, so the only significant factor is the tip contact point at impact.
Now, it is possible that a hard tip, especially if it is not holding chalk very well, will have a miscue limit closer to the center than a soft tip that is holding chalk well. In this case, the soft tip will enable a player to apply more spin to the CB since the tip contact point can be farther from the CB’s center without resulting in a miscue. Also, if one thinks a hard tip can’t hit as far out on the ball (even if it can), one might tend to hit will less tip offset from center, which will result in less spin.
There are many factors related to tip hardness that could influence squirt, including: tip density/weight, tip efficiency, contact time, and effective endmass. “Return of the squirt robot” (BD, August, 2008) documents an experiment related to the effects of tip hardness on squirt. A softer tip did seem to create slightly more squirt, but the experiment was not very well controlled (see the article for more info). In general, if the contact time is longer (as is the case with a softer tip), the effective endmass and resulting squirt should be larger (see the rubber-super-ball-tip report as an example). Another set of more careful experiments documented in the Cue and Tip Testing for Cue Ball Deflection (Squirt) video and “Cue Tip Squirt Testing” (BD, June, 2014) seem to imply that tip type, hardness, and height have very little effect on shaft squirt. Among the wide range of tips tested in the video, the harder tips did result in slightly more squirt. This makes sense because the harder tips are denser and heavier, creating more “endmass.” The shorter contact time seems to be less of a factor than the added weight.
Another factor involved with a softer tip is that it might better absorb glue and adhere to the ferrule more strongly and making it less likely to come off with lots of use and/or abuse.
A comparison of the hardnesses of tips of various brands can be found on the cue tip hardness chart resource page.
from Mike Page (in AZB post):
I am well aware there is an entire lore surrounding this notion that a soft tip gets more action, gets higher spin-to-speed ratio — and that you can find the claim from amongst the best players in the room, the best players in AZ Billiards, pro players, experienced players …
I think this claim should enter the textbooks as a superb example of confirmation bias: http://skepdic.com/confirmbias.html
Aside from the subtle contact-time effect on the offset (a smaller effect than the claims), the claims are false.
The force that produces the speed and the force that produces the spin are the same force, and at a given offset any additional force increases the two in the same ratio. A soft tip acts slightly longer, but it’s basically less force acting over a longer period, and the added-up result is the same.
There are shots designed to test the maximum spin-to-speed ratio, where you can get an actual top player trying to get maximum action using different tips–basically a slightly-off-angle draw shot where you are trying to hit a rail as far back as possible. I and others have done these empirical experiments, and the results have been consistent and agree with the expectations from the physical description.
from Mike Page:
Even if soft and hard tips held chalk exactly the same, it’s possible the soft tip might reduce the chance of miscue. For instance, suppose a miscue occurs when less than 50% of the contact patch has chalk. If the bald regions are small, then this standard may be violated more frequently for a hard tip with its small contact patch.
from Bob Jewett:
One issue is which harness of tip will allow the farther-from-center hit. Some believe that a soft tip takes chalk better so it can hit the ball farther from center.
There is a counter theory, and that is because a softer tip will have a longer contact time than a hard tip. During contact, the tip rides around the side of the ball some, so the final eccentricity as the tip leaves the ball is larger than when the tip first hits the ball. A softer tip, with the longer contact time will be farther off center at the end than a harder tip with the same starting offset. If both tips can only hold to a certain point of offset, and you start your shot so the miscue point is barely reached at the end of contact, the average offset will be larger for the harder tip. This means that the harder tip can create more spin for a given ball speed.
Which dominates? Holding chalk better or starting farther off-center? I don’t know of any experiment that has tested this.