Can grip pressure affect the cue ball during tip contact?
The short answer is: No.
HSV A.34 shows the hand grip during a firm stroke, striking the cue ball at the bottom of the pendulum swing. It is not totally clear from the video, but the hand flexes well after the cue ball is gone, as the hand accelerates the cue after it is slowed by the ball. Some additional video, with recorded data showing the post-hit acceleration, can be found here: stroke acceleration. The cue tip is in contact with the cue ball for such a short period of time (see tip contact time), and the hand flesh is so flexible compared to the cue tip, the grip cannot have any significant influence during tip contact. After impact, the grip hand does not generate much force until the cue slows and the hand moves forward enough (due to its momentum) to create enough skin flex. Again, the CB is long gone by the time this happens.
Also, any force that the grip hand might be exerting on the cue during contact would be too small to have any meaningful effect anyway compared to the extremely large force between the cue tip and CB. And many (if not most people) are exerting very little force with the grip right before contact anyway since the cue has already reached the desired speed at contact with the ball. That is clear in the acceleration plots in the various resources on the stroke acceleration resource page.
NV B.96 – Grip and bridge technique and advice (at the 2:32 point in part 2) shows how the bridge hand can also have no significant effect. The bridge hand flesh doesn’t yield until a transverse elastic wave travels from the tip to the bridge after cue tip impact … or during, if the bridge is within about 6 inches of the tip (for more info, see shaft endmass and stiffness effects). But even if the bridge is close to the tip (which usually isn’t the case), it takes time for the fingers to flex and generate force, and it takes time for that force to be “felt” by the tip. The CB will be long gone by the time this happens.
Bottom line: The CB is long gone before any “flesh effects” can be “felt” by the tip.
See also: grip technique advice.
from Patrick Johnson:
Stroke and grip can’t increase tip/ball contact time; the tip “bounces off” the CB on impact and your fleshy hand can’t stop it no matter how tight your grip or how much your stroke is accelerating.
Even if you could increase tip/ball contact time this way, the effect on CB spin would be tiny.
Can you get more cue ball speed with a tighter grip?
A tighter grip (if it is really tight) can effectively add more mass to the cue. So if you can deliver the cue to the ball accurately and with power, a tight grip could result in faster cue ball speed. However, a tighter grip usually results in less cue speed (and less accuracy) for most people.
Tightening the grip during the stroke, as some people do on the break and other power shots, might also result in slightly more power by activating slight wrist flick and maybe slightly more elbow flex (due to extra biceps contraction), both of which can add a little power.
from Spiderman (concerning whether grip tension has any effect):
Not on the cue, it doesn’t. But it has a big difference on how you play.
I think it’s been both theorized and verified that the impulse force during the brief contact far overshadows anything you can do by accelerating/influencing the cue during contact. There was a long thread on this last week.
On the other hand, from a shooter’s perspective, a loose grip encourages you to let the cue travel naturally in line without swoop or wobble, and keeps you from shoving it off-line with a poor stroke. Almost everything will work better with the loose grip, but it isn’t because of anything that happens during contact. It’s because it makes everything before contact work in better harmony. It helps your “real” stroke follow the exact path of your warm-up strokes rather than being a somewhat-independent event.
If you could keep the cue flowing perfectly in line with a tight grip, it would work just fine, but most people can’t do that – they will unintentionally pull it off-line. A tight grip also seems to sometimes manifest itself in a really bad habit where you try to “take something off” your stroke just before contact, and the decelerating cue condition is very prone to missing your intended tip-contact point. People who “take something off” are much more likely to miscue when trying to play the edges of the cueball. Next time you miscue during a low soft draw, ask yourself whether you tried to pull your stroke just before contact. That is far less likely with a loose grip.
There are times when a tight grip is appropriate – for example, a nip draw to avoid a foul – but loose seems best for normal strokes.
For years I’ve had problems with tight grip and eye control (where I look during warm-up and delivery). I’m still working on both, and the more I work on it the better I shoot.