Plain HSS (M2) softens at around 600°C. HSS-Co M35 contains 5–8% cobalt, raising the red-hardness threshold to about 700°C, letting the drill keep cutting in stainless, mold steel, titanium, and other work-hardening alloys. Cobalt drills cost ~50% more than plain HSS but last 3–5× longer in hard materials.

The 118° standard point needs a centre punch or pilot hole to start without wandering. The 135° split-point self-centres on flat or inclined surfaces with no centre punch. Use 135° SP for production drilling, hard materials, or any time setup speed matters; 118° is fine for casual hand drilling.

H7 is the ISO standard tolerance band for a basic-hole fit. At 10 mm nominal, an H7 hole is +0.018 / 0 mm — between 10.000 and 10.018 mm. It's the default fit for press-fit bearings, dowel pins, and bushings paired with a k6 or h6 shaft. A reamer ground to H7 size will produce that tolerance band with correct pre-drilling, speed, and feed.

Leave 0.2–0.4 mm of stock on diameter. Example: drill 9.7 mm before a 10 H7 reamer. Too little and the reamer rubs oversize. Too much and it chatters and risks chipping. For carbide reamers, leave 0.1–0.2 mm.

For sheet metal and thin stock up to about 4 mm thick, yes — a step drill produces a clean hole, deburrs the entry, and leaves a 90° chamfer ready for a countersunk fastener in a single pass. It is not designed for hard materials or solid stock above ~4 mm depth.

A U-drill (indexable insert drill) uses two replaceable carbide inserts instead of a ground HSS body. It runs at 4–6× the surface speed of an HSS jobber and replaces inserts rather than the whole tool when worn. Best for CNC machining centres with through-coolant capability in diameters above 13 mm. For one-off work or small diameters, an HSS jobber is cheaper; U-drills shine in production volume.

Always for lathe centre work or any time you need a precise hole position. For 135° split-point drills on flat surfaces, you can often skip it. For 118° drills on round stock, inclined surfaces, or when hole position tolerance is tight, a centre-drilled spot prevents the drill tip from wandering.

These are DIN standards for drill length. DIN 338 is the universal jobber length. DIN 1897 is short/stub length — more rigid, better for precise hole position and CNC. DIN 340 is long-flute — for deep holes (5×D and beyond) or stacked workpieces.

A countersink cuts a conical recess (typically 90°) so the head of a flat-head screw sits flush. A counterbore cuts a flat-bottom cylindrical recess so the head of a socket-head cap-screw (SHCS) sits flush. The screw head shape determines which one to use.

Three rules: run at 50–70% of drill RPM (not faster); feed steadily at 2–3× drill feed-per-rev; use cutting fluid even on aluminium. Spiral-flute reamers chatter less than straight-flute on cross-holes and interrupted cuts.

Yes — we keep YG1 Multi-1 and Cobalt drills in stock for the common 1–13 mm sizes. Larger sizes (14–30 mm), parabolic flute, taper-shank (DIN 345), MT shank, special coatings, and OEM ground-to-print drills are available on order with 2–3 week lead time from YG1 Korea.

Yes. We send drills and reamers to our partner re-grinding service in Sharjah. Typical turnaround is 5–7 working days at roughly 25–40% of the cost of a new tool. Solid carbide drills above 6 mm and machine reamers above 8 mm are usually worth re-grinding; smaller HSS drills are typically cheaper to replace.