Rules of Thumb in Pool

Bob Jewett

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....
Throw When Balls Are Close – Bob Jewett
If the balls are a quarter-inch apart, there is no throw or cut, no matter how you hit them.
...
Here's an update on this rule of thumb since Dr. Dave actually did the analysis....

The actual distance is exactly 3/8 of an inch (and not 2/8 or 1/4).

Surprisingly the rule does not depend on how dirty the balls are at least for fairly full hits into the back ball because the balls will be gearing before the end of the shot.

Here is the related page on Dr. Dave's site: https://billiards.colostate.edu/FAQ/combination/small-gap/

Patrick Johnson

Fish of the Day
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Here's an update on this rule of thumb since Dr. Dave actually did the analysis....

The actual distance is exactly 3/8 of an inch (and not 2/8 or 1/4).

Surprisingly the rule does not depend on how dirty the balls are at least for fairly full hits into the back ball because the balls will be gearing before the end of the shot.

Here is the related page on Dr. Dave's site: https://billiards.colostate.edu/FAQ/combination/small-gap/
Thanks for the update, Bob - hope it results in some more ROTs added to this great thread.

pj
chgo

Patrick Johnson

Fish of the Day
Silver Member
Here's one that will go down in obscurity:

To avoid hitting on a tip's edge, it should be shaped to a curvature radius less than its width.

For example:
- a 13mm tip needs a curvature with a radius less than 13mm - a quarter
- a 12mm tip needs a curvature with a radius less than 12mm - a nickel
- a 10mm tip like mine (similar to a snooker tip) needs a dime radius

pj
chgo

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jay helfert

Shoot Pool, not people
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While reading through some older Bob Jewett BD columns, I noticed that Bob uses a number of "rules of thumb". I find them very helpful and decided to gather as many of these together as I could. Below are fifteen rules of thumb that I gathered from various places. The names that I have credited for these represent the first place I saw them - not necessarily an original source. I don't really know the original sources for these.

If not stated clearly, please correct them as you see fit or ask for clarification, if necessary. I hope you find them helpful too. Would you like to add any to the pool of knowledge?

90 Degree Rule – Dave Alciatore
The first and most well-known reference line is the tangent line predicted by the 90 degree rule. For a stun shot (aka a “stop shot at an angle”), where the cue ball is sliding with no top or bottom spin at object-ball impact, the cue ball will head exactly in the tangent line direction, which is perpendicular to the object-ball direction.

Avoiding Double Kisses – Freddie The Beard
When the balls line up on a straight line to the middle of the FACING of the corner pocket (the facing on the long rail), the bank is a dead kiss. It is extremely difficult to beat the kiss when the balls are on a line to the middle of the FACING.
When the balls line up on a straight line to the MIDDLE of the back of the POCKET, there is no kiss.
When the cue ball and an imaginary ball at the contact point for the bank are on a line to the center of the pocket, there is a dead kiss if you use follow with no English.
These kisses are usually easy to evade by using English or draw to send the cue ball on a non-kiss path.
The aim on the object ball must be adjusted to allow for the ball action needed for a non–kiss bank.

Throw When Balls Are Close – Bob Jewett
If the balls are a quarter-inch apart, there is no throw or cut, no matter how you hit them.

6:1 Rolling Cue Ball Ratio – Bob Jewett
The ratio of about 6:1 is a useful rule of thumb when playing soft position. Suppose the object ball is six diamonds from a pocket, and you want the cue ball to follow straightforward not more than about one diamond after the collision. If you just get the object ball to the pocket — six diamonds of travel — the (rolling) cue ball will roll forward about one diamond. Another way to state this is that on a full, soft follow shot, the cue ball will go forward one ball for each diamond the object ball travels. At a later time, Bob gives the ratio as 7:1.

Ball in Hand – Bob Jewett
With ball in hand, you should never place the cue ball for a draw shot.

Two Rail Banking – Bob Jewett
If a ball is sent along roughly a 45-degree angle between the short rail (first) and the long rail (second) it will go close to two rails into the corner.

45 Degree Rule – Dave Alciatore
If the CB rolls into the short rail at roughly a 45-degree angle, it will head fairly close to the center of the table after contacting the long rail.

Importance of Rolling Cue Ball Through the Center of the Table – Danny Basavich
A cue ball rolling through the center of the table for position cannot scratch unless coming directly from the direction of a pocket (or first hitting at least one more rail). Stated differently, unless the cue ball is rolling straight from a pocket, it cannot scratch directly in a pocket after passing through the center of the table.

Banking Frozen Object Balls – Bob Jewett
If the cue ball is straight out from the frozen object ball, the ball has to be at least one diamond up the rail from the target pocket for the bank to be possible using all techniques.

Half Ball Carom (30 Degree Rule) – Dave Alciatore
If the object ball cut angle is anywhere from 15 degrees to 45 degrees, a rolling cue ball is deflected by very near 30 degrees from its original path.

Equal Distance – Bob Jewett
After a half ball hit with a rolling cue ball, the cue ball and object ball will travel a similar distance.

Shortening Banks By Hitting Firm and Full – Bob Jewett
Banks that are dead using a mirror system (for example from diamond 3 to diamond 1.5), can be shortened by hitting full and firmly (for example, diamond 3 to diamond 1). The idea is if you can get the shot to match the mirror system by subtracting 1 from the cue ball's location, the bank is "on" for the system. So, if you subtract 1 from cue ball's 3, you get 2-to-1, which is a standard mirror bank. Therefore it is “on” for a full, firm bank.

Cue Ball Deflection On Nearly Full Shots – Bob Jewett
If you cut the object ball just a little to one side (3/4 ball or fuller), a rolling cue ball will be deflected about three times the angle to the other side. For example, a five degree cut to the left will result in the cue ball being deflected to the right about 15 degrees.

Path of Rolling Cue Ball After Hit – Shawn Putnam
This is a system to predict the direction the cue ball will go on a rather full hit (about ¾ ball or fuller) after rolling into the object ball with follow. To send the cue ball in a particular direction, visualize the spot on the far side of the object ball that points to where you want the cue ball to go and then aim the cue ball to that point on the far side of the object ball.

Sidespin/Squirt Ratio – Bob Jewett
Two tips of English will produce twice the squirt angle of one tip.

One correction I see so far - You absolutely can bank a frozen object ball less than a diamond away from the pocket (up the rail) with the cue ball straight on. It's not a hard shot on a Diamond table.

One other thing to keep in mind when playing position for the next shot. It's always better to play position with the cue ball rolling along the position line as it approaches the ideal spot as opposed to rolling across the position line.

One other thing I just noticed. It is definitely easier to play position rolling forward with the cue ball but in some BIH situations a draw shot is the only way to get there.

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jay helfert

Shoot Pool, not people
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Here's one that will go down in obscurity:

To avoid hitting on a tip's edge, it should be shaped to a curvature radius less than its width.

For example:
- a 13mm tip needs a curvature with a radius less than 13mm - a quarter
- a 12mm tip needs a curvature with a radius less than 12mm - a nickel
- a 10mm tip like mine (similar to a snooker tip) needs a dime radius

pj
chgo

This is good Patrick. Did you know that it can make for a better hit to have a very small flat spot in the middle of the tip? Only a few players are aware of this. It will give you a better hit when using center ball. No, I don't know why, but it does work. I'm sure someone will show me the physics why I'm wrong but so what.

Patrick Johnson

Fish of the Day
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... it can make for a better hit to have a very small flat spot in the middle of the tip... No, I don't know why
Probably because your stroke can be off a tiny bit and still hit center ball...?

pj
chgo

BC21

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When cutting a ball that is close or frozen to the rail, and using outside spin, hit the ball thicker/fuller than you think you should hit it.

Patrick Johnson

Fish of the Day
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When cutting a ball that is close or frozen to the rail, and using outside spin, hit the ball thicker/fuller than you think you should hit it.
Of course this is true no matter how close or far from the rail the OB is. The same rule holds for using inside spin (hit thinner).

My rule of thumb for rail-frozen OBs is "hit them like any other shot" (i.e., fuller with outside / thinner with inside). The "thinner with inside" hit works because the rail compresses enough to give a little room for the overcut.

pj
chgo

dr_dave

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Here's one that will go down in obscurity:

To avoid hitting on a tip's edge, it should be shaped to a curvature radius less than its width.

For example:
- a 13mm tip needs a curvature with a radius less than 13mm - a quarter
- a 12mm tip needs a curvature with a radius less than 12mm - a nickel
- a 10mm tip like mine (similar to a snooker tip) needs a dime radius

pj
chgo
Obscure, but interesting ... and useful to know. FYI, I've added a quote along with your previous excellent contributions on the cue tip size and shape resource page.

Good job,
Dave

dr_dave

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Did you know that it can make for a better hit to have a very small flat spot in the middle of the tip? Only a few players are aware of this. It will give you a better hit when using center ball. No, I don't know why, but it does work. I'm sure someone will show me the physics why I'm wrong but so what.
The advantage of a flat center on the tip is you will get a center-ball hit even if your tip is unintentionally off center a touch. The disadvantage is if you intentionally want to apply just a touch of spin, you will not get any.

There was a guy in a pool league I was in years ago that had a tip that was almost perfectly flat. He never got much spin on the ball, but he pretty much always got a center-ball hit, even when he wasn't aligned well or had stroking errors.

Regards,
Dave

jay helfert

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The advantage of a flat center on the tip is you will get a center-ball hit even if your tip is unintentionally off center a touch. The disadvantage is if you intentionally want to apply just a touch of spin, you will not get any.

There was a guy in a pool league I was in years ago that had a tip that was almost perfectly flat. He never got much spin on the ball, but he pretty much always got a center-ball hit, even when he wasn't aligned well or had stroking errors.

Regards,
Dave

That makes sense.

BC21

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Of course this is true no matter how close or far from the rail the OB is. The same rule holds for using inside spin (hit thinner).

My rule of thumb for rail-frozen OBs is "hit them like any other shot" (i.e., fuller with outside / thinner with inside). The "thinner with inside" hit works because the rail compresses enough to give a little room for the overcut.

pj
chgo

Yes, it also applies to shots farther away from the rail.
But I never consciously aim to hit thicker unless the ob is close or frozen to the rail. Maybe because the pocket is so much smaller from the rail and my auto/subconscious adjustment for spin isn't enough. I have noticed over the years that many players struggle with rail shots and outside english. Make yourself aim thicker and you'll quit missing those shots.

Referring to the bold....I do not aim thinner for inside english cuts. I guess it's my cue, or stroke, but I always aim thicker when using inside spin. I play with a Mezz, LD shaft.

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dr_dave

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Referring to the bold....I do not aim thinner for inside english cuts. I guess it's my cue, or stroke, but I always aim thicker when using inside spin. I play with a Mezz, LD shaft.
There is a difference between where you aim to have the CB hit the OB and how you align your cue to send the CB to that position. When somebody says to aim a rail cut shot thin, they are referring to where the CB should hit the OB (or the cushion before the OB).

Regards,
Dave

dr_dave

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There is a difference between where you aim to have the CB hit the OB and how you align your cue to send the CB to that position. When somebody says to aim a rail cut shot thin, they are referring to where the CB should hit the OB (or the cushion before the OB).
For those interested in learning how to align the cue to have the CB go where you want when using sidespin, lots of useful advice can be found here:

how to compensate your aim when using sidespin

Regards,
Dave

skogstokig

AzB Silver Member
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alex lely made a good coaching point about shooting spot nine-balls, or below spot nine-balls, from an uptable angle. some people prefer hitting them soft with follow, and some (most pro's i would think) prefer hitting them medium-hard, two rails out with whitey. his point was: pick one and stay with it.

the same goes for many similar situations. myself i like shooting a last ball that is straight or near straight with a touch of draw. it doesn't affect accuracy, but since it's a repeated routine it removes insecurity in a pressure situation.

BC21

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There is a difference between where you aim to have the CB hit the OB and how you align your cue to send the CB to that position. When somebody says to aim a rail cut shot thin, they are referring to where the CB should hit the OB (or the cushion before the OB).

Regards,
Dave

Ok. I'm talking about the aiming of the actual stroke, the alignment of the cue stick as it strikes the cb.

If someone tells me to "aim" thinner, that tells me my aim line (where my stroke is aligned to) should be farther away from the ob. If they mean the cb should hit the ob thinner, then they should say the shot needs a thinner hit, which may or may not require aiming your stroke thinner. It's ambiguous for sure.

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Patrick Johnson

Fish of the Day
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I do not aim thinner for inside english cuts.
Inside spin increases throw for fuller hits, but too much can actually reduce throw for thinner ones (any inside spin reduces throw for half ball or thinner cuts) - so it might be correct to not aim thinner for many inside-spin shots.

For maximum throw (with a sliding CB):
- no cut: half of maximum inside spin
- from no cut to half ball: less and less inside spin as cut gets thinner, until...
- half ball cut: no spin
- thinner than half ball cut: some outside spin (less than "gearing")

pj
chgo

Luxury

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In 8 ball with ball in hand and no problem balls, start with the balls in the center of the table as they are furthest away from a pocket and may be difficult to make late in the run.

Sent from my iPhone using Tapatalk

BC21

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Inside spin increases throw for fuller hits, but too much can actually reduce throw for thinner ones (any inside spin reduces throw for half ball or thinner cuts) - so it might be correct to not aim thinner for many inside-spin shots.

For maximum throw (with a sliding CB):
- no cut: half of maximum inside spin
- from no cut to half ball: less and less inside spin as cut gets thinner, until...
- half ball cut: no spin
- thinner than half ball cut: some outside spin (less than "gearing")

pj
chgo

Too much thinking. I don't think about throw. It takes care of itself with speed and spin. I just put the cb where it needs to be in order to pocket the ob. I do this by aiming my stroke accordingly, depending on whether or not I'm using english. In other words, I don't aim with the cb, I aim with my stroke/cue alignment. I thought everyone did.

On a dead 1/2 ball shot....If I stroke through the center of the cb I am aiming my stroke through the vertical center of the cb to the ob edge. If I use max inside english my stroke is more aligned toward the middle of the ob, due to squirt. I'm aiming thicker in order to put the cb where it needs to be.

I wouldn't muddy it up by saying I am "aiming thinner" to account for throw because I'm using inside spin. Throw was already accounted for when I looked at the shot and determined where the cb needed to be in order to pocket the ball with the intended cb spin applied.

I've told many players to aim thicker on close to the rail shots when using outside spin, and they get it with no confusion.