Troubleshooting Views: 11

A non-round (elliptical) chamfer has these common causes and fixes: 1) Tool runout - mis-clamping or spindle runout makes the cutting path non-circular; fix: re-clamp, check collet and spindle, shorten overhang; 2) Workpiece not secure - movement or shift during machining; fix: clamp firmly, add support; 3) Feed too fast - fast entry deflects the tool; fix: reduce feed, cut in slowly; 4) Dull tool - high cutting force deflects the tool; fix: re-sharpen or replace; 5) Weak machine rigidity - deflection on old or small machines; fix: lower speed and feed or use a more rigid machine; 6) Sloped surfaces - a standard countersink contacts one side first on slopes; fix: use an angled-hole countersink (spot facer) or center-drill first; 7) Pilot hole not round - a worn drill or wandering drill leaves a non-round pilot hole; fix: check pilot quality, use a sharp drill; 8) Asymmetric edges - multi-flute tools with uneven edges cut non-round; fix: check tool quality, use certified tools, keep symmetry when re-sharpening. Work through these points and the problem is usually solved.