Extra hole
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Definition
Extra holes are used to fine tune reaction of a bowling ball.
- Extra holes are optional when considering a layout.
- A maximum of 1 extra hole is allowed per ball
- Maximum diameter is 1 3/8" including bevel
- No limit to extra hole depth
- Small extra holes drilled deep have more of an effect on ball reaction than large shallow extra holes. This is due to the small deep hole taking out some of the core of the ball, this causing a change in differential and radius of gyration.
Extra holes can fine tune a reaction based on the distance from positive axis point, midline and vertical axis line (VAL). Extra holes are usually placed on a line through the bowier's positive axis point, horizontally that reference line is the midline, vertically that reference line is the vertial axis line. The effect of the extra hole is enhanced when placed on these reference lines. See figure 1 for details regarding the location of PAP, VAL and Midline.
Flare Increasing Extra Hole
A flare increasing extra hole is located past the positive axis point on a line parallel to the midline (Figure 2 numbered location 1).
This location of the extra hole offers and increase in mid-lane, backend reaction and flare.
The further away the extra hole gets from the positive axis point at a limit of 3 3/8", the greater the influence on reaction.
Another location for a reaction enhancing extra hole is below the positive axis point (PAP) on the vertical axis line(Figure 2 numbered location 2). Reaction is enhanced on this line in the midlane, but backend is diminished compared to the hole past the PAP on a line parallel to the midline.
Flare Decreasing Extra Hole
A flare decreasing extra hole is located on a line parallel to the midline before the positive axis point.
Flare. midlane and backend reaction are diminished with this extra hole location (Figure 2 numbered location 3).
Another location for a reaction reducing extra hole is above the positive axis point on the VAL (Figure 2 numbered location 4). An extra hole placed on this plane offers the least track flare, midlane and backend reaction. The further away the extra hole gets from the positive axis point at a limit of 3 3/8", the greater the influence on reaction.
Megamav 23:22, 8 August 2007 (EDT)
