Shop Operations: Chamfering and edge dressing

The expression “There’s more than one way to skin a cat” certainly applies to machining. A young programmer in our shop is constantly being run in circles by the whims of those in authority. Newcomers are in a difficult position; they not only lack experience, they generally want to please everybody.

For example, there are numerous ways to apply edge dressings to a part, and some work better than others. Presented here are methods that may make it easier to apply these common features.

Shown is an inconsistent chamfer on an inside radius. This was because the Z height of the chamfering tool wasn’t set correctly. All images courtesy J. Harvey.

Chamfering is not as easy as it looks on a computer. The point of a sharp chamfering tool does not cut well and will generate a burr if programmed to cut on center around the profile of a part. This is because not much chip clearance is available at the end of a pointed chamfering tool and the cutting speed at the tip of a pointed tool is, theoretically, zero. Also, the tool tip may not be precisely sharp.

For a chamfering tool to cut cleanly, the tool tip must be offset from the profile. In a new version of the CAM software I use, a chamfering tool can now be offset to cut a clean profile.

If you offset a chamfering tool to cut cleanly, the depth of the tool must be correct. If the depth is not correct, the tool can produce inconsistent chamfers on the inside radii. This can be overcome with thoughtful planning. However, when it boils down to trivial features, I don’t like to think too much. I prefer to let the computer do the thinking.