COBALT DRILL BITS SEARS FULL
Therefore I strongly suggest you purchase your M42 drills from a quality supplier, not from knock-off sources - and then only the sizes you need if the purchase of a full set is not clearly indicated. It's the metallurgy that makes the difference in drill performance and while budget Asian import tooling is improving with time their metallurgy can be dubious. For the unscrupulous importer “cobalt” drills are just one more gimmick to extract money from the naive home shop purchaser.
It's only when we get them to the shop and attempt to sharpen one can we tell by the sparks (sparse red-orange streamers) and abrasion resistance (high) if we bought the genuine article. Whether they actually perform as well as an honestly presented cobalt bearing HSS alloy (M42 or equivalent) we have no way of determining by appearance alone. Thus we see "cobalt" HSS drill sets at low-price importers. Marketers are quick to pick up popular misconceptions and exploit them ruthlessly. In the end the new cobalt drills perform no better than your beater set. The thrill fades after some use and a few hasty free-hand sharpenings. Of course new drills work great because they are fresh and sharp from the factory and there is the "placebo effect" associated with every new purchase. What kind of performance improvement can you expect? So you buy a set of cobalt drills for about triple the price of an equivalent quality HSS set. The old set at home might be dull or it might be a cheap set purchased on impulse from an import seller. One may be attracted to the cobalt drills sold in sets at the big box stores some with colorful coatings. There are some myths about cobalt drills.
Cobalt HSS offers no advantage in drilling wood, mild steel, and softer non-ferrous metals. Unless you're drilling stainless, very hard bronzes, heat-treated alloy steels, or titanium alloys, so-called "cobalt" drills are overkill. Consequently, chip clearance will be more of a problem when using cobalt drills especially when drilling deeper holes. Cobalt HSS drills are intended for severe duty meaning they are made with thick webs and smaller gullets. They feature “red hardness” and hold their edges when drilling the toughest materials. Here's words shamelessly exerpted from my next HSM article:Ĭobalt HSS drills are intended for stainless and hardened alloy steels where heat and abrasion are factors in the cutting environment.
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