Inside Spin

Why do some people like to use inside spin or english, even on shots where it is not required for position?

First of all, the type of spin is usually dictated by cue ball position requirements for the next shot, so inside spin will not always be the right choice. Otherwise, here are some possible reasons to favor inside spin or english (IE) when other sidespin is not required (or when no sidespin is required):

  • Some people tend to undercut shots by aiming fuller than the shot requires, and inside english will create squirt that increase the resulting cut angle slightly (although, spin-induced throw will tend to counteract this some).
  • A small amount of IE can counteract the effects of cut-induced spin on the cue ball, possibly resulting in a more natural and predictable rebound angle off a cushion.
  • IE can transfer “helping” or “get-in” spin to the OB, which can help rail cut shots enter the pocket more easily.
  • With very steep frozen rail-cut shots, IE makes the shot much easier; and with very steep non-frozen rail-cut shots, there is less chance of fouling by missing the ball.
  • Swerve resulting from IE (especially with more cue elevation) straightens the angle of a shot, which makes the cut easier and can be used to better hold the CB.
  • IE can narrow the follow angle of a cut shot (see below).
  • IE increases throw at small cut angles, but actually reduces the amount of throw at larger cut angles.
  • The amount of throw with IE can be much more consistent than with outside english (OE) if the amount of english varies a little. In other words, the amount of throw varies more with tip placement for OE vs. IE. This might explain why some people prefer using IE on cut shots … because they can better anticipate and adjust for the amount of throw.
  • The least amount of throw, and the most throw consistency, occurs with fast IE shots. See the 2nd plot on page 3 of TP A.28, which corresponds to 30° cut-angle stun shots at different speeds and varying amount of both outside english (positive in the plots) and inside english (negative in the plots). In the plot, notice how consistent and small the amount of throw is for fast-speed inside-english shots over a wide range of sidespin amounts (see the left side of the green curve, which is very low and level).
  • With IE, especially at higher cue elevations, swerve reduces the effective cut angle of the shot, and margin for error is larger with a smaller cut angle (see cut shot margin for error).
  • IE generally reduces OB angle error (i.e., there is more room for CB angle error) and makes it more consistent, as compared to outside spin (see TP B.30).

For more information, see TP B.30 – Is Outside Spin More Accurate Than No Spin or Inside Spin?, “Throw – Part VII: CIT/SIT combo” (BD, February, 2007), the throw resource page, and the squirt, swerve, and throw effects summary page.

However, when one uses english, in addition to adjusting for throw, one must also adjust for CB deflection resulting from squirt and swerve (see squirt and swerve effects). These effects vary with shot shot speed and distance, type and amount of spin, cue elevation, and conditions, so using inside english when it is not required for CB control is probably not a good approach for most people.

Is using a “touch of inside” a good idea in general?

Per the info above, inside spin does offer slight advantages for certain types of shots, however, using a very small amount doesn’t really take advantage of these slight advantages. If the CB will hit a cushion, sidespin is used to change the rebound angle. If you don’t want any change in rebound angle (because you like the direction the CB will head into and away from the rail), you do need to use a touch of inside spin to prevent cut-induced spin on the CB from changing the rebound angle. Otherwise, the direction and amount of sidespin is chosen to make the CB go where you want it to go. For an example, see:

Why does IE increase throw at small cut angles and decrease throw at larger cut angles?

Let’s start with a very small cut angle to the right, but almost straight. With no sidespin, the amount of throw will be very small and to the left slightly. With inside (right) sidespin, the OB will throw to the left a lot more; and with outside (left) sidespin, the CB will throw to the right. So in this case (a small cut angle), inside english obviously increases throw.

With larger cut angles, outside english can create throw either right or left based on whether the amount of english is greater than or less than the “gearing” amount. The following video demonstrates this effect:

HSV B.33 – Outside english gearing, and cut and spin-induced throw

Inside english always throws the OB in the same direction because the spin is in the CIT direction. However, CIT and SIT don’t add like some people might think. The following article provides explanations, illustrations, and examples:

“Throw – Part VII: CIT/SIT combo” (BD, February, 2007)

At small cut angles and small amounts of sidespin, the CB and OB sort of stick together during contact. However, at larger cut angles and/or with lots of inside english, the CB is sliding against the OB during contact. Friction (and therefore throw) is less when the sliding speed is greater. That’s why throw is actually less when you add inside with a larger cut angle, because spin increases the sliding speed during contact. For more info, see: throw speed effects and the following example:

The following video demonstrates most of the important throw effects, showing how throw (CIT or SIT) varies with angle, speed, and the amount and direction of spin:

NV B.86 – Cut-induced throw (CIT) and spin-induced throw (SIT), from VEPS IV

For detailed explanations, illustrations, and examples of all throw-related effects, see the article and video links in items 15-36 under the videos here:

squirt, swerve, and throw effects

Is inside english a better choice than outside english to limit CB sideways drift on some shots?

The following video demonstrates several examples of this principle:

The reasons why inside follow narrows the carom angle are:

  • the CB swerves into the OB causing the CB angle to straighten slightly (and more with more cue elevation).
  • the added surface contact speed at impact reduces friction between the balls (see throw speed effects), which:
    • creates less throw, allowing for a slightly fuller hit.
    • results in less topspin loss, allowing the CB to follow more.

Here are two more pertinent videos:

Also see the outside-english CB hold resource page.

from Colin Colenso:

Inside english is often useful in taking the CB 2 or 3 rails. Often in these situations it heads for open space into the middle of the table. With a little practice this is quite predictable and leaves a player better next shot options.

For the draw with inside they may be doing this to check (hold) the CB angle off the rail. It may allow them to hit the shot a bit firmer without risking losing the CB, and by hitting it a bit harder, they avoid the risk of leaving whitey too close to the rail.

Also, inside can be very useful in getting the CB down table from say a 3/4 ball shot down the long rail.

Inside has similar throw to rolling follow so long as you don’t play it too soft or from too straight on. Advanced players often utilize it. Intermediate players seem to love their OE, whereas advanced players are often weary of it, other than using a touch to gear away the throw, particularly on soft stun shots.

Why are inside-english shots more difficult for some people?

from Patrick Johnson:

It’s a combination of things:

1. You use it less often (partly because you’re not as good with it).
2. You use it for different (often more difficult) shots.
3. You use different spin with it (usually high vs. usually center or low).
4. You hit it at a different speed (usually harder).
5. It’s less self-correcting.

Pay attention to these things while practicing inside and outside shots and you’ll get better at inside pretty quickly.

A specific suggestion: pay attention to exactly where your stick is pointing on each shot compared with the CB/OB contact points – as you make and miss shots it will help you see the exact differences in how to aim them (it also helps generally to build accurate “shot memory”).

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