Milling machines are much heavier duty and sturdier than drill presses, due to support column size and thickness. They also have larger quills that allow the user to mill oval thumb holes in bowling balls with no taper. Milling machines also allow the user to "drive" thumb slugs and inserts into the ball without removing the ball from the jig. Milling machines will normally accomodate a keyless chuck, which is nice for speedy operation.
Furthermore, milling machines with multi-axis jigs allow the user to drill all 3 holes without unlocking the bowling ball. This allows for the most precise alignment possible, and is the most accurate setup in repeating drilling specs time after time.
Milling machines are approximately 4 feet by 4 feet and weigh just over 1000 pounds.
Drill presses simply will not allow the user to drill an oval hole consistently through different densities and materials. The quill and column are not large enough to withstand the vibration and movement created by the milling process. When you are using a drill bit to shave a small amount of material out of a thumb slug that is already drilled, the point of the bit is not being supported by anything. This means that you must have a large and sturdy machine to withstand the movement and drift created by this. Drill presses do not allow for this.
Drill presses are much smaller units, and typically weigh around 300-400 pounds.
The machine that Strapper is talking about is most likely a "Hinetani" machine. They are monstrous machines that are very hard to find at this point. The drill bits are extremely expensive and rare. Make sure not to lose them!
If anybody else has any questions about drill presses and milling machines, please feel free to e-mail me or call me.
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Jeff Ussery
Powerhouse Training Clinics
www.proshoptraining.comPro Shop Help Desk Hotline - 785-843-2658