Fitting “thumb out”

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TonyPR
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Fitting “thumb out”

Post by TonyPR »

Hello and Merry Christmas to all. I have a question regarding fitting:

What are the causes and what can be done to fix/eliminate a slight space between the thumb web and the ball? Is it necessary that there is absolutely no space in that area?

I am talking about a bit of separation between the web and the ball, maybe 1/4”, I can see it if I take video and pause it, a bit of light can be seen between the ball and the hand in that area.

Spans are correct (up to line midpoint between creases) at medium stretch (not slack nor tight as a banjo string).

She needs a lot of forward thumb to hold on to the ball, very flexible all over the hand, I call her Gumby.

Current grip is:
Full spans
RF 4 1/16
MF 4
Thumb 1/2 Forward, 0 Lateral
Fingers 1/4 forward
Finger laterals MF 1/4, RF 1/2

Releases well at good speed without grabbing, thinking if it ain’t broke don’t fix it but can’t get rid of the doubt if it could be better.
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TomaHawk
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Re: Fitting “thumb out”

Post by TomaHawk »

My only thought would be, if the knuckle (MCP joint) is sitting on top of the ball there would be a slight gap between the web and the ball.

A little more bevel might eliminate the gap issue. Another method to enlarge the thumb hole at the top would be to use a larger drill bit to accommodate the knuckle and drill the top of the hole 1/8" + or - deep with that drill bit, chamfer the hole as necessary.
TonyPR
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Re: Fitting “thumb out”

Post by TonyPR »

Thank you TomaHawk, makes perfect sense, MCP joint can definitely be in, will chamfer the back of the hole.
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EricHartwell
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Re: Fitting “thumb out”

Post by EricHartwell »

I'm not a fitter but in hindsight TomaHawk's recommendation is exactly what I use to make my fit feel secure.
I use Lots of bevel all the way around the thumb hole so I can bury my thumb completely and feel secure in the ball without squeezing it.
I never thought about the gap between the thumb web and the ball.
My method is to use my bevel knife to carve it to shape and size.
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Re: Fitting “thumb out”

Post by JimH »

There is a danger of creating too much bevel and having the hole larger than 1 1/4 inch. I saw a ball inspector at a tournament challenge a ball with a large amount of bevel. The ball passed the inspection but the bowler was very upset. Be careful.
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Re: Fitting “thumb out”

Post by EricHartwell »

But it is not a balance hole.

My switchrip hole is 1-3/8"

I bevel all the way to the outside edge of my insert.
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Re: Fitting “thumb out”

Post by JimH »

If a tournament inspector decides the hole is in excess of 1 1/4 inch then the ball might be declared illegal. Of course you can challenge the inspector, and sometimes that will work. The best thing to do is make sure a tournament inspector does not find anything to declare the ball illegal.
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Re: Fitting “thumb out”

Post by EricHartwell »

I would hate to go to Nationals and get all my equipment denied.

Cut and pasted from...
http://usbcongress.http.internapcdn.net ... lebook.pdf

"7. Drilling Requirements. All balls used in USBC certified competition must meet the following requirements:
1) Holes.
a) Holes or indentations for gripping purposes
i) Shall not exceed five and shall be limited to one for each finger and one for the thumb, all for the same hand.
ii) Shall not exceed 1-9/16” diameter and 4-1/2” deep, including holes required to install removeable devices.
iii)Must be used on every delivery."

This actually allows the Turbo Switchgrip where you need an 1-1/2" hole to install.
I could actually bevel all the way to the outside of the outer sleeve.
Which I actually do to make sure it is below the outside radius of the ball.
My driller's plug cutter isn't the sharpest.
He actually starts that beveling process by taking his sander to smooth that edge.

I think I am ok.
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Re: Fitting “thumb out”

Post by JimH »

Thanks for correcting my error of using the old rule of 1 1/4 inch for the maximum hole size. The point is that an inspector might disqualify any ball that excedes the maximum hole size due to beveling.
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Re: Fitting “thumb out”

Post by TomaHawk »

JimH wrote: January 2nd, 2022, 2:40 pm Thanks for correcting my error of using the old rule of 1 1/4 inch for the maximum hole size. The point is that an inspector might disqualify any ball that excedes the maximum hole size due to beveling.
It's anybody's guess what an USBC official might declare illegal.

Two of my customers actually have thumb sizes that are larger than 1 1/4, not small guys by any stretch of the imagination. I think it would be hilarious if an official was to try and tell either one of them, their ball is illegal.
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Re: Fitting “thumb out”

Post by JimH »

Several years ago at the European Championships a legal ball was disqualified. The tournament rules said each ball must be USBC approved and be listed on the USBC website. One ball was made for conditions commonly found in Europe and sold only in Europe. The ball was USBC approved but not marketed in the USA and consequently not listed on the USBC website The ball was disqualified, a team manager contacted the USBC to confirm the ball was USBC approved. The USBC wrote back that it was approved. The tournament ball inspector still rejected the ball.
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