When you need to drill holes close to each other, the holes are often the same size. But what do you do if one or more of the holes is a different size from the rest? Different size holes presents many problems. Some of these challenges are tool RPM speed, thrust and feed differences, the need to change out tooling more often on some processes and more. Our Recommended Tool Speed Chart can help determine the best tooling speeds for high-speed tooling in many materials and provides conservative numbers that should be safe for use even in manual drilling processes such as those on a drill press, etc.

When the suggested RPM for the different size tools is significantly different, the chance for tool breakage and other issues exists. Our multiple head designs can solve many of the problems of drilling two or more different size holes. Custom designed multiple spindle heads do not require any tool changes since two separate tools can remain in the spindles yet run at different RPM rates. Running each tool closer to its optimum speed also increases the tool life because it changes the amount of material taken out per rotation as well. When drilling different size holes simultaneously with a Multiple Spindle Drilling Head, the spindles can often be made to different lengths to compensate for tooling length differences. in many cases, this will keep the side loads on the drilling head and the tooling to a minimum. By controlling the side loads, smaller tooling is less likely to be broken off in the chuck. It also often allows for drilling straighter holes and drilling more precise patterns.

Typically, drill tooling is available in three lengths. These are known as screw machine length, jobber length and taper length. Small drill breakage can be reduced or even eliminated by using screw machine length tooling whenever possible. The shorter the tool, the more rigid it will be and the less likely it is that you will snap it off in most cases.

Here are some charts listing the dimensions for the standard drill lengths:

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