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Metal fabrication asks more of a drill bit than occasional work in wood or plastic. Bits need to start accurately on steel, clear chips without overheating, and hold up across repeated holes. The right set depends on the metal thickness, hole sizes, and whether you drill by hand or on a drill press. For most shop work, a well-made set of high-speed steel (HSS) bits is a better buy than a large assortment of bargain bits with sizes you rarely use.
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Choose the right bit material
Standard HSS bits are an economical choice for mild steel, aluminum, and other common shop metals. They work well when kept sharp and used at sensible speeds. Cobalt HSS bits cost more but tolerate heat better, making them useful for stainless steel and repeated work in tougher alloys. Cobalt is not a magic cure for poor technique: a dull cobalt bit can still rub, overheat, and burn the work.
Black-oxide finishes can offer modest corrosion protection and help with chip flow, but they do not make a basic HSS bit equivalent to a cobalt bit. Titanium-nitride-coated bits can last longer if the coating remains intact; sharpening removes that surface coating at the cutting edge. For a small shop that sharpens bits, uncoated HSS or cobalt is often the more practical choice.
Compare drill-bit sets
| Set type | Best for | Trade-off |
|---|---|---|
| HSS jobber-length set | General holes in mild steel and aluminum | Lower cost; less heat-resistant than cobalt |
| Cobalt HSS set | Stainless steel and frequent metal drilling | Higher upfront cost; still needs careful speed and feed |
| Step-bit set | Clean, larger holes in thin sheet metal | Limited to its stepped diameter range; not for thick stock |
| Reduced-shank set | Larger holes with a drill chuck limited to 3/8-inch capacity | Less convenient for small holes; large bits demand more torque |
A general-purpose HSS metal drill-bit set is a sensible starting point for a bench that mostly handles mild steel and aluminum. Look for clearly marked sizes, a sturdy case, and a useful range rather than the highest bit count. A set covering fractional sizes from 1/16 to 1/2 inch is versatile, though many fabricators use a smaller core range most often.
Match the set to the work
For regular stainless work, consider a cobalt drill-bit set. It costs more, but improved heat tolerance can pay off when drilling multiple holes in material that quickly work-hardens. If you only make an occasional hole in thin stainless, a sharp HSS bit may be adequate; spend the difference on cutting fluid and a safe way to clamp the stock.
Sheet-metal work is different from drilling through plate. A step-bit set makes a round hole in thin sheet without the sudden grab that a large twist bit can cause. Choose one whose steps include the diameters you need. Step bits are not a replacement for conventional bits in thick plate: the cutting geometry and limited step depth make that a poor, slow match.
If your work regularly needs holes larger than 1/2 inch, check the drill’s chuck capacity before buying. Some larger bits have reduced shanks that fit a 3/8-inch chuck, but the drill still needs enough torque. A compact cordless drill may struggle or twist violently if a large bit catches. Use a drill press or a suitable high-torque drill, clamp the work, and avoid holding a large drill in a way that lets it wrench your wrist.
Drill without burning bits
Punch the hole location first so the bit does not wander. For holes above roughly 1/4 inch in steel, drilling a pilot hole can reduce the load, but the pilot should be substantially smaller than the finished hole; an oversized pilot leaves the larger bit with little material to cut cleanly. Clamp the work securely, use cutting fluid on steel, and keep the bit cutting rather than spinning against the surface.
Use slower speeds as bit diameter increases. As a starting point for mild steel, a 1/8-inch bit might run around 2,000–3,000 RPM, while a 1/2-inch bit may need roughly 500–700 RPM. These are starting ranges, not guarantees; alloy, bit geometry, drill rigidity, and cutting fluid all matter. Stainless generally calls for a slower speed and steady feed. If the bit squeals, the chips turn blue, or the hole stops advancing, stop and check the speed, sharpness, and lubrication. Letting stainless rub against a dull bit can harden the surface and make the next attempt harder.
For a cordless drill, select a low gear for larger bits and use the side handle when supplied. Do not assume an impact driver is a substitute: many drill-bit shanks and metal-drilling tasks are better served by a drill with a conventional chuck, controlled speed, and appropriate torque. Wear eye protection, remove loose chips with a brush, and deburr the hole after drilling.
What to check before buying
Check whether the set includes duplicate sizes, fractional steps, or only a sparse selection. Fabrication often benefits from common fractional sizes, but numbered bits can be valuable for tapping holes; match the set to your fasteners and tap-drill chart. A split-point tip helps the bit start with less walking, though a center punch remains useful. Also inspect whether replacement bits are easy to buy individually. Replacing one frequently used size is usually cheaper than replacing an entire set.
For occasional mild-steel brackets, an inexpensive HSS set is fine if the bits arrive sharp and you replace or sharpen them when they dull. For daily work, stainless, or repeated holes in thicker stock, cobalt is a more defensible upgrade. For thin sheet, add a step bit rather than expecting a twist-bit set to do every job. That focused combination is usually more useful than paying for a huge assortment that spends most of its life in the case.