Manufacturer List -> Brunswick -> Low Differential Symmetric Core
Use X-holes to increase or decrease track flare learn more here
Note: Finger, Thumb and X-holes must have at least a moderate bevel and the riser Pin must be at least one in from any drilled hole to comply with the brunswick warrenty.
Early Rolling Reacting Layouts
Maximum hook potential for heavy oil
High-RPM players may not need the X-hole for maximum reaction. Add X-Hole if extra reaction is desired.
This layout may hit the finger holes for High-Track players, use layout 1L instead.
Medium hook potential
More length, softer backend and less hook than Layout 1E
This layout may hit the finger holes for High-Track players, instead use layout 2L instead.
Pin between axis and leverage for medium hook potential and early roll.
Helps moderate over reactions.
This layout may lack hitting power for Medium-Low RPM players.
Smooth reaction for moderating wet/dry lane conditions
Lower hook potential than layout 3E.
This layout may hit the finger holes for High-Track players, use layout 4L instead.
Later Rolling Reacting Layouts
Maximum hook potential with less mid-lane and more backend than layout 1E.
High-RPM players may not need the X-hole for maximum reaction. Add X-Hole if extra reaction is desired.
Medium hook potential
More length, softer backend and less hook than layout 1L.
High RG pin position with pin above the fingers for length. X-hole positioned for increased flare.
Moderate hook potential with skid/snap arc to fight the early hook in the heads.
Lower hook potential than layout 2L.
Minimum hook potential for dry lanes and moderating over reactions.
High RG pn position with the pin above the fingers for length.
Brunswick's ball drilling instructions include eight layouts; one group of four earlier rolling reactions (1E-4E), and one group of four later rolling reactions (1L-4L). Both groups contain layouts that adjust performance from high flare and hook potential to low flare and hook potential. Not levery layout is appropriate for all types of releases. Brunswick separates bowler's release characteristics.
- High-RPM players and Medium-Low RPM players. High RPM players rev the ball at rates greater than 300 RPM. On the men's tour, rev rates range from approximately 250-450 RPM. Most of the men's tour players you see on TV would be considered High RPM players. High RPM players can be sensitive to "over-flaring" which can make the ball hook early andbe inconsistent at the breakpoint. Brunswick recommends low to medium flare layouts for High-RPM players.
- High-Track players and Medium-Low Track players. High Track plyers have tracks within 1" of the thumb and finger holes and will usually have a horizontal axis measurement near 6" from grip center. Medium-Low track players have tracks that are greater than 1" from the thumb and finger holes and typically have horizontal axis measurements that are from 3 1/2" - 5".
After Determining your bowler type and ball reation needs see the table below for recommended layouts. The Symmetric Core layout sheet is dinto two columns for "Earlier Rolling" and "Later Rolling reactions.
| Track |
RPM Rate |
Earlier Rolling Layouts |
Later Rolling Layouts |
| High |
High |
3E |
All the Later Rolling Layouts can be used by all types of players |
| High |
Medium-Low |
No early Rolling Reactions |
| Medium-Low |
High |
2E,3E,4E |
| Medium-Low |
Medium-Low |
Brunswick recommends positioning the Heavy-Spot / CG to end up with 3/4 -1oz of positive side wieght and a small amount of finger/thumb weight (less than 1/4 oz.) after drilling. this leaves the driller plenty of room to modify the ball reaction with an X-hole, yet doesn't require than an X-hole be used to make the ball ABC legal.
