Triple-Fluted Drill Bits?

admin

I noticed again today that when I use a handheld-drill to make holes in thin sheet, the holes always end up not-quite-round, "three-lobed" due to the drill bit walking around while drilling. I use a gouge to make a starting hole, but that doesn't seem to make any difference. So what I want to know is, does anyone sell drill bits for a regular hand-held drill (small, 1/2" drill) in typical sizes (for that size drill) that have three flutes instead of two? I know there are milling machine bits that have 3-4-5 and more flutes, but I can't ever recall seeing 3-flute drill bits anywhere. Does anybody make them? ~
Reply:You can always use a unibit which is a stepped drill bit that works great in sheet metal.  You can get them at just about any big box store.  They aren't cheap but they usually drill from 1/8 - 1 1/8" you can get a range of sizes.  Do a search on "unibit" on google.  Nice to have one or two in your tool box.Jeff
Reply:Second the unibit. They kick butt. Don't go for the cheapy- had them at work and the life was very short.Three flute bits are not going to help. If the material is thin enough to lobe out the hole, all a three flute type will do is give more lobes. They also need a fairly clean pilot about 75% the finish size.
Reply:I forget who made it but there was a company that made a three flute drill that had an arraingment on the shank so that it could float laterally, but stayed paralell to chuck axis (NO I don't recall exactly how that worked)....But it did not drill round holes....it drilled nearly square holes for carrage bolts.When a bit chatters, you always get a lobed hole with one more corner than the number of flutes on the bit.
Reply:Originally Posted by kevboI forget who made it but there was a company that made a three flute drill that had an arraingment on the shank so that it could float laterally, but stayed paralell to chuck axis (NO I don't recall exactly how that worked)....But it did not drill round holes....it drilled nearly square holes for carrage bolts..
Reply:You can get 3 flute drills from MSC mscdirect.com.  We use them on stainless steel for a job that needed the extra strength in the drill.  I would use a unibit though for what your doing.Don
Reply:My favorite teacher in High School was Mr. Zinck, (wood shop) he had a lot of neat tricks.  For round holes in thin sheet with a regular drill bit, he took a small piece of cloth folded a couple of times, put that between the drill bit and a pilot hole. Experimenting with the size and type of cloth on a scrap test piece will be best. Keep the cloth small, or you will have a problem with "whipping" Honor the people that taught you, by teaching others.Just my  opinion, not from a book, just from the road.Howes Welding Inc.www.howesweldinginc.com