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Author Topic: Acceptable tolerances  (Read 4933 times)

Litespeed

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Acceptable tolerances
« on: January 30, 2007, 10:16:33 AM »
If you have multiple balls drilled by the same shop, how close would you expect the balls to match?  I'm currently looking at two balls that were drilled at the same place to the same sheet but the gap between the fingers on one is .400" on one and .287" on the other.  The span as best I can measure is off by about 1/8" as well.  I'm a fairly new bowler but have worked on cars, motorcycles and other mechanical things for a long time and know that with proper tooling the specs should be easily repeatable.  Just want to know if my expectations are to much or if I should start shopping elsewhere.  Thanks for any info.
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strikemor

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Re: Acceptable tolerances
« Reply #1 on: January 30, 2007, 06:29:41 PM »
If the ball is a conventional grip the normal distance between the fingers, or bridge, is 3/8".  For fingertip, it is 1/4".  The maximum variation I would allow in my shop is about 1/32".  As far as the span is concerned, I would expect the difference from ball to ball to be 1/32" or less.  If your pro shop is varying as much as you say, it is time to try someone else.
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raiderh20boy

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Re: Acceptable tolerances
« Reply #2 on: January 30, 2007, 06:45:42 PM »
Did you pay for it?? Sounds like that shop owes you a new ball and drill if they have a spec sheet for you. There are NO EXCUSES for that bad of a 'MATCH".
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solid9

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Re: Acceptable tolerances
« Reply #3 on: January 30, 2007, 06:58:50 PM »
Is there a chance that you are looking at different bevels, not actual drill distance ?
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Litespeed

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Re: Acceptable tolerances
« Reply #4 on: January 30, 2007, 07:07:50 PM »
Both balls are drilled fingertip.  I don't have a proper tool for measuring the spans so I used a sheet of paper with the edge firmly against the ball in a line that intersects the center of the thumbhole and the finger hole I was measuring.  I looked straight down from the top to ensure the I was measuring the inner edge of the hole and not measuring somewhere on the bevel.  I can't assure 100% accuracy doing it this way but I've come up with right around an 1/8" difference on many tries starting from scratch.  The distance between the fingers was pretty easy to check using a set of digital calipers.  I'm going to check in the garage and see if I can make a tool that will measure span better (don't need an absolute number, just a delta between the two) but it really doesn't matter since it's obvious the finger gaps are very different.  Thanks for the info since I now know what I should expect and won't be at the mercy of what they tell me.
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No Open Tenths

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Re: Acceptable tolerances
« Reply #5 on: January 30, 2007, 07:18:39 PM »
Just a thought... What balls are we talking about?
 The reason I ask is I can see a driller making the bridge a little wider on a ball that has had a reputation for cracking in an attempt to keep this from happening. I could be way off on this...
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rickc

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Re: Acceptable tolerances
« Reply #6 on: January 30, 2007, 08:29:28 PM »
You should expect all dimensions within 1/64".  If the dimensions are off as far as you say, I wonder how far off the pitch in each hole might be.  Good ball drillers scribe the ball when they layour the span and bridge to insure the greatest accuracy.  Crayon marks are too wide.
Drilling a ball isn't rocket science, however laying it our correctly for a particular bowler is a different story.
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Rick
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hskrntx

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Re: Acceptable tolerances
« Reply #7 on: January 31, 2007, 08:25:19 AM »
OK, truth to be told, instead of fiction, it all depends on how good the equipment is that the driller is using!  1/16 to 1/32 tolerence is not unusual!  Anything over that means the driller wasn't paying much attention to detail when he/she was drilling, or laying out, the ball(s)!  Free plug-and-redrill should be in order at the very least!
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Wilbert

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Re: Acceptable tolerances
« Reply #8 on: January 31, 2007, 09:18:20 AM »
I think 1/32 is ok.  When it gets to 1/16 it is borderline. Much more than that it is not too good.
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JohnP

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Re: Acceptable tolerances
« Reply #9 on: January 31, 2007, 09:41:23 AM »
Do the balls you'e comparing have finger grips?  If so, the grips in the old ball can easily be worn enough to make 1/8" difference in span and/or total bridge width.  If this is the case, compare the distances using the edge of the drilled holes.  --  JohnP
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Litespeed

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Re: Acceptable tolerances
« Reply #10 on: January 31, 2007, 01:49:47 PM »
The two balls are a hammer pain and a hammer tough.  Both are fairly new and have finger grips.  The measurements I took for width were using a digital caliper while gently pushing the inside edges of the inserts out of the way.
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Litespeed

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Re: Acceptable tolerances
« Reply #11 on: January 31, 2007, 01:55:20 PM »
Oops, that's a Hammer Tuff.  I will be taking them in tommorrow after work to be checked.  I'm pretty sure the PAIN (with a finger to finger span of .287" edge to edge) is properly drilled and the Tuff is the problem.  Not sure what to expect from the shop but I've had the Pain a little over a month and the Tuff is a couple weeks old, both bought brand new from them.  Luckily the cheaper of the balls is the one that will likely need to be corrected but I don't think I like the idea of having to plug and redrill a brand new ball because they messed up.  As a side note, the Toxic I ordered is supposed to be in Friday so at least I will have a bit of leverage with that.  I do unfrotunately think it will be my last purchase there though.
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Nollster

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Re: Acceptable tolerances
« Reply #12 on: February 02, 2007, 08:43:24 AM »
I've run into this issue quite a few times recently.  In fact, I had Ron C. check some of my equipment at the gathering last summer and found them to be off by over 1/4" on the spans!!  They tell me you can't tell the difference when it's 1/8" off, but I beg to differ...
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Edited on 2/2/2007 9:41 AM
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