Drilling Different Size Holes with a MultiSpindle Head
Close spaced holes tend to be uniform in size but there are situations where a drilling hole pattern contains two different hole sizes. Two different size holes presents many problems. Some of these problems include tooling, operating speeds and numerous manual tool changes. Our Recommended Tool Speed Chart can help determine the best tooling speeds for high-speed tooling in many materials.
When the recommended difference in tool speeds is large the normal compromise of reducing the spindle speed to that for the largest tool will seriously affect the pattern drilling time. The chance for tool breakage with the smaller sizes will also be increased. 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. A custom multi-spindle head can also be geared to allow the smaller tool to run at a faster speed. Running each tool closer to its' optimum speed increases the tool life. When drilling different size holes simultaneously with a Multiple Spindle Drilling Head the total of the spindle and tool lengths should be the same or as close as practical. This will keep the side loads on the drilling head and the tooling to a minimum. It will also reduce tool breakage of the smaller tooling, drill straighter holes and drill a more precise pattern. Drills are available in three lengths know as screw machine length, jobber length and taper length in increasing order. Small drill breakage can be reduced or eliminated by use of a short tool length. To keep the total spindle and tool lengths similar special spindle lengths can be provided. Our on-line charts listing the dimensions for the standard drill lengths are: 