In fact, I found HSS much more forgiving even on my precision watchmaking machinery. Carbides are composite materials made by sintering together hard particles of mostly tungsten carbide (WC) with a metal in powder form, mainly cobalt. Lesser quality steel will become blunt quickly. I believe there are also green bands, but I haven't a clue as to their usage, never had one. The plastic bands around the shaft are red = coarse, blue = middle, yellow = fine. You might have to twist their arm to sell you some, but most will happily agree. Often, a dental depot will sell burs and bits less expensive than a hobby shop. PS: I forgot to add, a wonderful source for every imaginable bit form/shape is from the dental industry. ![]() I've been acquainted with metal/carbide burs for 47 years. Whereas a bit used only for drilling holes will last 5 times longer. For instance, drilling small holes with a round bur does work, just the bur, even a carbide bur will dull soon. Also, using the correct bit for the deed is good advice. Their individual usage is for the most part a matter of speed used and/or material that needs cutting/grinding.įor drilling holes, for instance in brass strips, a drill press or at least some kind of device that keeps the rotating instrument steady is a must in most cases. The colored bands are only a reference to the coarseness of the individual bit. Lesser quality steel will become blunt quickly, they'll become more expensive than carbide soon.ĭave, the selection Toni showed is a wonderful collection. So a problem may not be a bad drill, but bad material.Ĭarbide is the only way to go. We modellers often seem to come across too soft qualities that catch drills. Some are easy to drill and others are a pain. HSS or SS (not recommended) drills in sizes below 1 mm can be quite pricey, particularly for sizes below 0.5 mm and those with thickened shafts (which are much better and easier to handle).Īnd: there are many different qualities of aluminium, brass and steel. Having said that, these carbide drills can be an economic option in sizes below 1 mm diameter due to their relatively low price and if you don't mind to bin a part from which you cannot extract a broken drill. In drill depths that exceed 3xdiameter, I would use them only with a screw-feed, not with a lever feed. They are unforgiving to wobbling in guiding the movement and to changes in feed. However, the traders rarely know the intended application of these drills, so you might get some from an aircraft factory intended for use with high-strenght aluminium alloys, or some from a printed circuit board plant, intended for use on glass-fibre reinforced epoxy resin.Īs noted above by vaddoc, carbide is brittle and normally requires rigid machines and a rigid set-up for their use. Also these are good enough for us modellers. The second stream are used ones that have been taken out of manufacturing processes in a scheduled way before they become dull and could spoil a work piece. One is that from 'seconds', meaning these are drills that did not pass the high quality standards of industrial sppliers, but that are still good enough for occasional use by people like us. There seem to be two major supply streams for carbide drills into the secondary market theses days. This applies particularly to model supply houses and the hundreds of 'ebay shops' that are around today. ![]() ![]() However, unless you buy from an established manufacturer, you may not be able to get this information. ![]() This concerns the cutting angles, secondary cutting angles, relief angles, the angle of the spiral, etc. In industry drills are shaped for the materials they are supposed to drill. There is actually no 'best' drill, only approriate ones, appropriate for the material and the conditions of application.
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