Standardize hole sizes to cut machining costs

One of the simplest ways to reduce part cost is to standardize hole sizes. Every unique hole size requires a separate drill, reamer, or tap, plus a tool change. These changes add cycle time and increase tooling inventory. The goal is to minimize the number of different hole diameters and thread types in your design.

Start by choosing common drill sizes like #10, 1/4 inch, or M6. Avoid unusual or custom sizes that force the machine shop to buy specialty tooling. When possible, design all clearance holes to use the same diameter. For tapped holes, stick to a few standard thread sizes. This reduces the number of tap changes and simplifies quality checks.

Consider a bracket with ten holes. If you use two different drill sizes, the CNC program can finish all holes in a single tool run. Using four different sizes would require multiple tool changes, increasing cycle time by minutes per part. Over a production run of thousands, those minutes add up to significant cost.

Additionally, use standard counterbore and countersink diameters that match common screw heads. Avoid deep holes when shallow ones work, as deep holes require longer cycle times and special tooling. By applying these principles, you reduce programming effort, tooling costs, and machining hours while making parts easier to manufacture.

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