View Full Version : what kind drill bits to use
02-18-2006, 11:29 AM
I am gonna start drilling out the rear rivets and will be using .120" bits. Just wondering what kind of bits everyone uses. I cant seem to locate any carbide bits. I wonder if titanium bits will work when using my drill press.
02-18-2006, 12:12 PM
you can really use any drill bits as long as you step drill and use oil. just go slow, keep your bits cool, and don't be forcefull, there is nothing worse than breaking off a drillbit
ozzy the nuke
02-18-2006, 12:15 PM
I have several sets of bits in different grades and I prefer standard high quality high speed steel bits for drilling out trunnion rivets. Low grade bits are either too soft, in which case they dull too quickly. Or they are too hard and break too easily. The titanium is just a coating. If the underlying metal is not good, the bit will still be no good, even if it is titanium coated. This is the case with most cheap titanium bits. The toughest and hardest bits are cobalt. The problem with these is that they are so good that if I get off track while drilling out the rivet, the bit will drill right into the trunnion without warning. A high quality HSS bit is optimum. They are hard enough for drilling rivets and if of good quality, will also be tough. The nice thing is that they will make a chirping noise and dull if they start hitting the trunnion. If I press on, the bit will dull, but the trunnion wont be ruined. If I press too far, the bit will break. So....I use good quality high speed steel bits and go gently or stop if I hear chirping. Most often, cutting fluid will let them follow the trunnion wall. I end up with a rivet that is drilled off center, but the trunnion hole wont be enlarged at all. As for what brand of HSS, I like Hansen (now under the Irwin name).
02-18-2006, 12:37 PM
I have a set of sears cobalt bits. I like these for drilling out rear trunnion holes. Just have to make sure you're centered. I drill a smaller hole into the rivet about halfway in, and flip it over to do the other side. This seems to relieve pressure. I then just punch them out. Once I have some rivet poking out the other side i get some vise grips and twist & pull to get them all the way out. No real risk of drilling into the trunion that way.
02-18-2006, 02:06 PM
The problem with these is that they are so good that if I get off track while drilling out the rivet, the bit will drill right into the trunnion without warning. .
Been there. Trashed a trunnion that way.
02-18-2006, 02:46 PM
Thankyou for the replies. I will be buying some HSS bits. The last thing I want to do is to damage a trunion.