Counterboring

I use counterboring for bolt head seats and spot facing for sealing surfaces after deep hole drilling. Both operations are done after the main bore is complete. Getting them wrong means the fastener does not seat or the seal leaks — either one scrapes the part. Counterboring Deep Holes Counterboring enlarges the entry of a hole to create a flat-bottomed recess for a bolt head or cap screw. The counterbore has a pilot that fits the existing hole to keep the counterbore concentric with the bore. I use a counterbore with replaceable pilots so the same cutter body works for different hole sizes. ...

I use step drilling when the bore needs multiple diameters along its length. Step drilling creates a bore with different diameters at different depths, like a counterbore for a bolt head or a stepped shaft bore for hydraulic applications. It can also help manage chip evacuation and tool deflection in deep holes. When to Use Step Drilling vs Single Diameter Step drilling is not always the right choice. I use it in specific situations where a single-diameter hole will not work. Here is how I decide. ...