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USBC equipment specifications manual

http://usbcongress.http.internapcdn.net/usbcongress/bowl/equipandspecs/pdfs/ESManual.pdf

So can he just plug a thumb hole and call it a day?

Ahhh so confusinggg stresses!!!

Unless the ball had a lot of thumb weight I doubt it will be legal just by plugging the thumb hole.  If finger weight turns out to be illegal you may e able to drill the finger holes deeper to meet the specs.

Remember, if he ever uses the thumb hole, say when he shoots a spare, the ball must meet static weight limits based on both a grip center between the finger holes and the standard grip center.  --  JohnP

100% this is the rule= your only allowed 1 hole that is not being used so if he throws 2 fingers and there is a thumb hole and no weight hole its ok or if there is no thumb hole there has to be a weight hole you cant have a thumb hole and a weight hole and not be using either of them. rule only allowed 1 hole thats not being used

squirrelywrath1
Bowling tape is the only thing allowable in balance holes!
BOWL.com | 10
Last updated on 12/14
Plugs and Designs
1.
Ball plug or slugs may be used for the purpose of re-drilling a ball. When a slug is used, there
must be a hole drilled completely through the slug leaving no void at the base.
2.
In all cases, there shall be no interior voids.
3.
Plugs and designs must be made of material similar to, although not exactly the same as,
the original material out of which the ball was made. Plugs and designs must comply with
other specifications of a bowling ball.
4.
No foreign material may be placed on the outer surface of the ball or in the balance hole, in
-
cluding but not limited to paint, marker or whiteout. Bowling tape is acceptable in a balance
hole.

Ken De, for the most part if you have a ball drilled with 2 finger holes a thumb hole and a weight hole most likely just by plugging the weight hole the ball will not be legal im sure do to to much side in the ball and you dont want to drill your ring finger any deeper if possible because that only weakens the ball reaction on the ball.    the density of the weight block weights more then what the plug you fill the hole with so  make the hole deeper and then fill the hole back up with epoxy so that way you can fine tune it by drilling the ring finger to make it back to no more than 1oz of side.   I have been drilling for no thumb bowlers for over 20 years and I have yet to see what there advantage was over a person that used there thumb other then USBC didnt like the fact that a no thumber had an extra hole in there ball. I look at it now by there new rule the person that puts there thumb in the ball has more options on how there able to drill a ball over a person that does not put there thumb in the ball.  like I told USBC back in July 2014  If I drill a ball to fit my hand with a thumb hole and a weight hole and I dont use my thumb its illegal but  what makes the difference to a person that throws the same ball with there thumb and the balls legal USBC said there is no difference in how that balls gunna perform be the way either person throws it with or with out there thumb in the ball  other than 1 person that throws the ball with and 1 does not  but the ball weights totally different going from middle of fingers as to going from middle of the span  whats the diff?    If you need any help just send me an IM  there are still ways around what USBC allows you to do with a ball that still stays with in all there rules thats on paper.. as you can see  the PBA bowlers are the 1s that went to USBC president Andrew and wanted this rule changed, look whats happened since  Belmo is still winning PBA tournements  so I guess that backfired on them after all...  LOL  like I said  there are still ways your able to drill up equipment these days to still make it an avantage over a person that puts there thumb in a ball..  I think out side the box every day for new and better ways around what they say you can and cant do.. its a part of life   ask the guys in Nascar,  they do the same thing every day..