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Thread: Drop Ball Sizes

  1. #1
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    Question Drop Ball Sizes

    Hello!

    This should be very simple, but I seem to be having trouble figuring it out...

    What is the standard size drop ball for industrial lenses (basic impact) in the USA?

    I am trying to get a new 1" drop ball tube from a company I won't name, and they keep sending me a 7/8" tube labelled, "Industrial 7/8". The drop-ball I am replacing is 1".

    1" is correct, right? Or am I losing my mind?? What is a 7/8" drop-ball for, anyway?

    In summary, what is the correct drop-ball for the following lenses:

    Dress Glass
    Industrial Non-poly (Glass, Plastic, etc)


    Thanks!!

    ~Sleepy Lab Rat

    ---
    "Facts are meaningless. You can use facts to prove anything that's even remotely true!" --Homer Simpson

  2. #2
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    Go to (at home or on the web) a ball bearing supplier (or even a truck repair place they will have ball bearings any almost any size and weight and when these are replaced they are happy to give them away as they are not reused. In otherwords most ball bearings are in a race with lots of balls, when one goes bad they throw the whole part away but trucks (or large machinery) is more likely to have the large diameters you require.

    Chip:cheers:

  3. #3
    RETIRED JRS's Avatar
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    If you follow Chip's advice, then you need to make sure the 5/8" (dress wear) STEEL ball weighs no less than 16 grams. FDA guidelines state both numbers. I think the industrial size is 7/8" or 1".

    I don't have my copy of the report handy or I'd be more definite on the industrial number. Sorry.
    J. R. Smith


  4. #4
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    Thanks, that's a great tip, what what I really need to know is whether I need a 1" or 7/8" ball!

    Thanks!

  5. #5
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    Lenses are divided into two categories:

    Basic Impact
    •25.4mm (1 in)steel ball
    •Dropped from a height of 127cm (50 in)
    • The lens shall not facture
    •Minimum thickness 3.0mm except for those
    lenses having a plus power of +3.00 D or greater
    shall have a minimum thickness no less than
    2.5mm
    •Plastic lenses only -Penetration Test
    •44.2gm (1.56oz)weighted projectile
    •Dropped from a height of 127cm (50 in)
    •Lens shall not fracture or be pierced

    High Impact
    •Impacted with 6.35mm (0.25in)steel ball
    •Velocity of steel ball 45.7 m/s (150 ft/s)
    •Lens shall not fracture and no piece shall be
    detached from the inner surface
    *Special Note:Optical Laboratories must be certi .ed to
    process High Impact Lenses
    •Plastic lenses only -Penetration Test
    •44.2gm (1.56oz)weighted projectile
    •Dropped from a height of 127cm (50 in)
    •Lens shall not fracture or be pierced
    Joseph Felker
    AllentownOptical.com

  6. #6
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    Thanks, Joseph! That's exactly what I thought - do you know what a 7/8" ball would be for??

  7. #7
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    Thanks, Joseph! That's exactly what I thought - do you know what a 7/8" ball would be for??
    No.
    Joseph Felker
    AllentownOptical.com

  8. #8
    Bad address email on file bbla's Avatar
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    The 7/8" or 1" ball is for testing Industrial safty thickness lenses
    Bill

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