Cobalt vs Hss Drill Bits: Which One Should You Buy?

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Below: what separates cobalt from plain high speed steel, when each material earns its place, and four cobalt sets compared by size range, piece count and storage.

Cobalt vs hss drill bits: what actually differs

High speed steel, shortened to HSS, is the base material for both kinds of bit in this comparison. A cobalt bit is still high speed steel, but with cobalt added to the alloy: the listings here describe M35 high speed steel with 5% cobalt. That addition raises heat resistance and hardness, which is why cobalt bits keep cutting in stainless steel and hardened metal where plain HSS dulls and loses its edge. The Sinyeenglon listing puts hardness at up to 67 and claims a life up to 12 times that of the average HSS titanium coated bit, a claim made in the context of that hardened-metal set.

Point geometry matters alongside material. The CaRoller and SEDIANAS listings describe a 135-degree split point with a round straight shank, a self-centering design that prevents walking when the bit starts. Fully ground twist design, named by both listings, clears particles faster and decreases friction and heat for cooler drilling. Those features appear on some cobalt sets in this guide, and material also affects how long the edge survives in hard stock.

When cobalt earns its place

Cobalt earns its place on hard, high tensile strength material. The SEDIANAS listing names stainless steel, cast iron, high temperature alloy, titanium alloy and hard plastics as the ground where M35 cobalt succeeds, and the Sinyeenglon listing adds zinc alloy, hardened metal, mild steel tube, flat bar and aluminum to the same list. The LingGan listing covers stainless steel, iron, copper and aluminum, plus cast iron, and describes outstanding wear resistance in high-intensity work. If the job list includes stainless brackets, hardened bolts or cast iron parts, cobalt is the material to reach for.

Heat is the other reason. The LingGan listing describes advanced heat resistance for high-temperature environments, and the SEDIANAS listing credits M35 with superior heat resistance and greater hardness compared with ordinary drill bits, extending service life when drilling hard materials. A bit that stays hard when hot keeps its edge through a long hole in stainless, while a bit that softens starts to rub and dull.

When plain HSS is enough

Plain HSS is enough for softer materials and lighter drilling. Wood, plastic sheet and mild steel do not punish an edge the way stainless and cast iron do, so the extra hardness of cobalt buys little there. The CaRoller listing itself names wood and plastic sheet among the materials its cobalt set drills, which shows cobalt can do soft work, but the value case for cobalt rests on hard metals. For a garage that mostly drills wood, plastic and thin mild steel, the hard-metal advantage of cobalt matters less.

Piece count and size range often matter more than material for soft work. A set that covers the sizes drilled most often, with spares in the small sizes that snap, beats a harder set with gaps in the range. The sets below show how cobalt sets handle that problem, from a compact metric set to a 99-piece case with duplicates in the small sizes.

The gear: four cobalt sets compared

LingGan Metric Cobalt Drill Bits Set: a 13-piece M35 set in metric sizes from 1.5mm to 6.5mm, with 5% cobalt for wear resistance in high-intensity work. It suits stainless steel, cast iron, copper and aluminum, and its straight shank fits a mechanical or hand drill. The compact range covers small hole sizes.

CaRoller Cobalt Drill Bit Set: a 29-piece M35 set from 1/16 inch to 1/2 inch, with an amber coating, a 135-degree split point and a round straight shank. It comes in a cup-type holder with a built-in clip that attaches to a tool belt, keeping bits within reach on a job. Materials named include stainless steel, cast iron, high temperature alloy, titanium alloy, hard plastics and wood.

Sinyeenglon Cobalt Drill Bits Set: a 99-piece M35 set from 1/16 inch to 3/8 inch, in a plastic index storage case with sizes printed on the bottom of the lid. Small sizes carry duplicates, with 16 pieces at 1/16 inch and 16 pieces at 5/64 inch, so a snapped small bit does not end the job. Hardness is listed at up to 67, with a life claim up to 12 times that of the average HSS titanium coated bit.

SEDIANAS Cobalt Drill Bit Set: a 15-piece M35 set from 1/16 inch to 3/8 inch, with a 135 degree point tip, round straight shank and an index storage case. Its size list includes 2 pieces each at 1/16 inch, 5/64 inch and 3/32 inch, with single pieces through the larger sizes. It names hardened metal, stainless steel, cast iron, wood and plastic among its uses. The spec table lists a size range up to 1/2 inch, while the title and size list end at 3/8 inch.

Drilling hard metal: speed, fluid and angle

Technique also affects how long any bit lasts, cobalt included. The Sinyeenglon listing gives the clearest guidance: hold the bit vertical to the workpiece, control speed at a low range from 200 to 1000 rpm, and use cutting fluid to stay cool so the bit lasts longer. Low speed matters because high speed in hard metal builds heat faster than the edge can shed it, and heat is what dulls a bit.

Start on center and let the point do the work. A 135-degree split point centers itself and resists walking, but it still needs a steady hand and a vertical angle to the work. Cutting fluid keeps the cut cool, and a fully ground twist design helps clear particles faster. Pressing harder when the bit slows down adds heat; back off, add fluid and let the edge cut.

FAQ: garage tools

Can HSS bits drill stainless steel?

Plain HSS can start a hole in stainless, but it dulls faster there than cobalt, and the listings here position cobalt as the material for that job. M35 cobalt with 5% cobalt holds its edge and its heat resistance in stainless steel, cast iron and titanium alloy, which is why the sets in this guide are cobalt rather than plain HSS.

Do cobalt bits need cutting fluid?

Cutting fluid is recommended for hard metals. The Sinyeenglon listing states that using cutting fluid will stay cool and make the bit last longer, and the fully ground twist design named by the CaRoller and SEDIANAS listings helps clear particles faster and decreases friction and heat for cooler drilling. For wood and plastic, fluid is not part of the guidance given.

What speed should cobalt bits run at?

Low speed, controlled by the operator. The Sinyeenglon listing gives a range from 200 to 1000 rpm for its set, with the bit held vertical to the workpiece. That range is given for the Sinyeenglon set only, and the other listings in this guide give no speed range, so do not carry it across to every cobalt set as a fixed rule.

Are cobalt bits worth it for wood and plastic?

For wood and plastic alone, cobalt is more than the job needs, though the sets here do cover those materials. The CaRoller listing names wood and hard plastics among its uses, and the SEDIANAS listing names wood and plastic too. Buy cobalt for the hard metals in the drawer, and the soft materials are covered too.

How many pieces should a cobalt set have?

Enough to cover the sizes drilled most often, with spares in the small sizes. The sets here run from 13 pieces in metric sizes from 1.5mm to 6.5mm to 99 pieces from 1/16 inch to 3/8 inch, with the 99-piece set carrying 16 pieces at 1/16 inch and 16 pieces at 5/64 inch. A 15-piece or 29-piece set suits a garage that drills a narrower range.

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