I was wondering what the difference is between the error in face angle for say hitting a driver with a 100 mile swing speed (therefore assuming say a 280 yard shot and assuming square club path)within a 30 yard fairway and hitting a 5 or 10 foot putt in the hole? Is it comprable (i.e. 2 degree face angle on the driver would hit the fairway and a 2 degree face angle on the putter from 10 foot would make the putt)?

Dear David,

Driver face error and putter face error don't really compare in a straight-forward manner, because driver face error imparts side spin on a ball that travels thru the air, and this side spin in the air exacerbates error, whereas on the ground, putter face error does not result in side spin on a ball in the air -- the ball's rolling on the ground washes out the potential sideways error effect from side spin pretty quickly and completely.

Even so, the extent of putter face error for the distance of a putt has been discussed in detail in an earlier post on the Flatstick Forum. he bottom line is that for ever 1 degree of face error at impact, the line of the ball's roll deviates 0.21 inches off the intended line for each foot of rool. A 10-foot putt, then, misses off line by 2.1 inches. The hole is 4.25 inches wide, so any deviation greater than half this (2.125 inches) is too much. That is, a 1 degree face error will still find the hole at 8 feet, but not at 10 feet.

The same geometry applies to the driver if you ignore side spin on the ball traveling thru the air. (You also have to ignore any face "bulge" in the driver in which the face bows out with convexity from heel to toe, as this feature generates "gear effect" that reduces the effect of side spin. Some putter designs also have a similar convexity heel to toe.) But, for a 230 yard drive, which is 690 feet, the error offline in inches is 690 x 0.21 inches. That's 144.9 inches offline, or a bit over 12 feet offline (4 yards). This is the same as 0.63 inches offline for every yard of intended line (also 0.0175 yards offline for every 1 yard of intended center line.). Finally, for every 57 yards of intended center line, the ball flies offline 1 yard. Over 230 yards, that's a little over 4 yards offline.

Cheers!

Geoff Mangum
Putting Theorist and Instructor
Geoff Mangum's PuttingZone
http://puttingzone.com
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