Carbide Drill Bits & Drilling Tools for Metalworking

Cobalt bits are HSS alloyed with cobalt: hotter-harder than plain black oxide or HSS-G, self-centring at 135°, and the shop-standard answer for stainless by hand or on a drill press — an HSS drill bit for aluminum or mild steel is cheaper and cuts fine. Carbide goes further again: ten times the heat resistance and far more rigid, which is what a CNC spindle at feed needs on steel, stainless and cast iron. The trade is brittleness — a carbide drill walks in a hand-held drill, so match the material to the machine.

A drill cuts straight ahead at its tip and makes the hole; an end mill cuts sideways and can open, enlarge and profile that hole, so the two answers cover different questions (see our end mill vs drill bit comparison on the end-mill page). A tap never drills its own way: the hole must be pre-drilled to the tap drill size — one pitch under the major diameter, checked against the tap drill size chart here on the site. Hole first, thread second, with the drill and the tap quoted together.

Stainless work-hardens, glazes and drifts: use a solid carbide or cobalt bit with a split or 140° point, a chip-splitting flute, firm feed (don’t rub) and high-pressure coolant at moderate speed. That is the honest answer to the drill bits for stainless steel search — geometry and coolant matter more than the marketing word on the tin. Hardened steel above HRC 45 is different again: small pilot holes are possible on a rigid machine, but hardened features should normally be milled, ground or CBN-finished rather than drilled.

Black oxide is the budget HSS finish: mild steel and general maintenance work. TiN is the general carbide coating — wider temperature tolerance, lower friction. TiAlN and AlTiN hold their hardness at the heat stainless, titanium and hardened steel generate, which is why they are the default on production CNC. For aluminum, skip the coating: a polished uncoated flute avoids built-up edge entirely.

118° is the classic HSS jobber angle — inexpensive and general purpose, but the chisel edge walks, so pilot-punch or centre-drill first. 135° with a split point self-centres: it starts on a flat, hard surface without wandering, which is what you want on stainless and hard steel by hand. Solid carbide and U-drill pilot inserts run 140° — self-centring only if the setup is rigid, and worth it because they leave the roundest hole.

To about three diameters deep, external flood is usually enough. Past that, or in stainless, titanium and cross-holes, a through coolant drill puts fluid on the cutting edges and pushes chips out of the hole instead of letting them drag back down the flutes. If the machine has no internal coolant, peck-drilling with air or MQL is the fallback — and for aluminum, a polished uncoated bit with a strong air blast beats coolant most days.

Drills are sourced from vetted tooling partners and inspected before dispatch. Diameter, point geometry, coating and shank are confirmed against the quotation, dimensional reports and material certificates are supplied on request, and each shipment is packed for transit. If a batch does not perform as confirmed, send the batch reference and your measurements and we will put it right.

The workpiece material and hardness, the hole diameter and final tolerance, the depth (or the ratio, like 3×D), the machine and its coolant system, and the coating or point geometry if you already run one. With those five points we can quote the drill, the pilot/reaming sequence and starting cutting data instead of a catalogue item.

Quotations are normally issued within hours during business hours — email and WhatsApp reach us directly. Orders ship worldwide from Guangzhou, China with tracking, and payment terms are stated on the quotation. Trial quantities and mixed-item orders — drills, reamers and spotface cutters on one PO — are both welcome.