Drill America #5 .141 Continuous Pilot Capscrew Counterbore, Dew Series | High Precision Counterbore Tool for Metalworking & Woodworking | Ideal for Professional Machinists & DIY Projects

I bought several sizes of these but will just leave one review for this size option. They are the typical import tooling, nothing fantastic but serviceable - these do work fairly well. Best if you can slow down the RPM of course so if you're using in a drill press the slowest speed on most presses will be too fast - use cutting oil and mind your feed and technique in that case. I ran this one for 13 holes in 6061 and it was no worse for wear other than clinging metal (normal). With a lucky fit, I later used it as a full bore reamer for some short stainless (304 I think) shaft collars and it did surprisingly well there other than surface finish but did take a toll on the cutting edges, which I was able to touch up well enough. I used one of the other sizes in nylon and it was only ok there...not quite sharp enough for a high quality cut in that material (may do better in delrin, not sure how it would like polycarbonate...probably frustrating in soft plastics).So...good value, worth the purchase for hobby or occasional use in common and/or softer materials. Have to use these correctly, don't treat them like they're drill bits.