Using a lathe to sharpen drill bits8/8/2023 ![]() ![]() ![]() I got this trick from an old machinist,and have used it to bore 2" or larger holes with my 16" lathe. But he did not want to print my method of holding large drills as it can be dangerous if you mess up. I left a bunch of tips on Tony Griffiths Engineering site. I do not want to be held responsible if someone attempts to do what I do,and gets injured,or gets his chuck ruined. I'll advise you instead to buy an adapter that fits your tailstock,and has a larger taper on it to fit your drill's taper. This will have trued up the cutting end of the drill so it has the point on center,and both sides will throw equal chips.Īctually,I just decided to not share with you how I hold large taper shank drills when my tailstock is too small a taper to accept them. The last little bit of steel is honed away with an India stone. Grind away metal until you get VERY close to reaching the cutting edge. You may need to put a collar on S&D bits to get them to register properly. Even horribly mangled bits can be resurrected in just a few minutes. This must be done at the bench or belt grinder. It automatically gives the clearance behind the cutting lip. Of course they have to have relief ground into them. What I do is chuck large drills in my chuck,and grind the tips with a tool post grinder until the cutting edges have both been fully ground by the tool post grinder. Of course,you can always resort to using a protractor and grinding freehand. That's 1mm per 2 seconds roughly.įeed these bits REAAAAAALLLLLLLLLLLL SLLLLOOOOOOOOOOOOOOOOOTo sharpen these large drills,it takes some equipment,though. Let's take half that feed in our home shops to get a little more life. Now your maximum feedrate is 2 inches per minute. Dremel or Proxxon spindle on your mill, which would be handy for this!), and try it at 2000 rpm. However, let's return to reality here (unless you have an aux. For carbide, a green wheel is okay for roughing or resharpening a masonry. All drills, whether carbon steel, HSS, or carbide, have to be ground to sharpen. You can feed a right smart 56 IPM to get that chipload at 56K rpm. No, its not possible to sharpen any kind of drill on a lathe, since a lathe is not capable of the motion necessary to put the required relief behind the cutting edge. That same #80 bit wants a chipload of 0.0005". When you break a tool, it's too much chipload. You can absolutely drill holes with a lot less speed than that, just trying to point out what the feeds and speeds look like. I dont have a Vol or issue number or a copy of the article. This kind of became the standard for small bit sharpening jigs. Brown wrote up his design for a tool for 4-facet sharpening of very small drill bits. V for Mild Steel 30, Cast Iron 15, Aluminium/Brass 40. Dumore and others made small "sensitive" drill presses that ran at 20-30K rpm for the purpose. D Diameter of drill/Cutter or work in the Lathe in MM. Applications that drill a lot of tiny holes all use very high speeds to do it. They want a surface speed of up to 200 SFM, which is far from burn up territory.Ī #80 (0.0135") bit needs to be spun at 56,000 rpm to hit 200 SFM if you run the numbers through G-Wizard. You almost can run those little drills too fast to burn them up, even HSS. Try boring a 1mm hole in a cylinder and you will see what I mean (1/2 size Tiny). I have been teaching this in Fitting and Machining in NSW TAFE for the last 25 years, plus been in the trade since '65.Īs for sharpening TINY drills, I use a magnifier and an OILSTONE where I can, Mind you I usually just get a new bugger (I buy 0.5 mm drills and smaller 10 at a time and for small drilling use a Dremel in a work stand).ĭont worry about this too much, take it easy with little tools/jobs. ![]() Light touch is needed as others have said. Most drill presses only go to about 3000 revs, so be carefull out there. What can be seen from all this, is that a small drill needs buckets of rpm. You can either sharpen the drill bit, or, if the given their relatively low cost, simply buy another one Twist drills are used for most of the work we do. Machine tools do not give exact revs anyway. Dont worry about converting 10 mm to inches, call it 3/8ths. The Value for V in this calculation is in M/Min. V for Mild Steel = 30, Cast Iron = 15, Aluminium/Brass = 40.Įxample 10 mm drill in Mild Steel - 300 * 30 / 10 = 900 RPMġ0 mm drill in Cast Iron - 300 * 15 / 10 = 450 RPMġ mm drill in Mild steel - 300 * 30 / 1 = 9000 RPMġ mm drill in Aluminium - 300 * 40 / 1 = 12000 RPMĠ.5mm drill in Brass - 300 *40 / 0.5 = 24000RPMĥ0 mm (2 inch) dia in Mild Steel - 300 * 30 / 50 = 180 RPMįor use with CARBIDE TOOLING, multiply V by 3-4 D= Diameter of drill/Cutter or work in the Lathe in MM. To work out RPM for drilling/milling/lathe work.įormula RPM = 300V/D where V = cutting speed of MATERIAL being machined. ![]()
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