Metal Drill Bit - PROJAHN, HSS-Co 5%, Ø 3.0 mm, DIN 338, 250300

PROJAHN HSS-Co 5% Metal Drill Bit, Ø 3.0 mm, DIN 338, 250300

PROJAHN 250300 is a Ø 3.0 mm metal drill bit from the HSS-Co ECO Line, to DIN 338, short series with a cylindrical shank. Overall length 61 mm, flute length 33 mm. EAN 4000146250037.

What HSS-Co 5% means

The steel is alloyed with 5% cobalt. Cobalt holds hardness at high temperature - exactly where plain HSS begins to soften. In practice this is the bit for stainless steel, hardened and tough alloys, where HSS-G goes blunt on the first hole.

135° split point

The point is ground at 135° with a split point, which PROJAHN applies from Ø 3.0 mm upward - so this size already has it. A split point self-centres: the bit does not wander on the surface and in most cases needs no centre punch. The flatter 135° angle cuts more aggressively than the classic 118° and behaves better in hard material.

h8 tolerance and ground finish

The shank holds h8 tolerance and the bit is ground, not rolled. A ground bit is cut from bar stock, so the geometry is more accurate and it runs with less wobble in the chuck. At Ø 3 mm that matters - thin bits break from run-out more than from anything else.

Short series

61 mm overall with a 33 mm flute is the short DIN 338 series. A shorter bit is stiffer and deflects less. For material up to about 25-30 mm thick this is the right choice; deeper holes call for the long DIN 340 series.

Speed at 3 mm

Thin bits want high speed and light pressure, which is the opposite of instinct. At Ø 3 mm in structural steel the order is about 1500-2000 rpm; in stainless, half that, with cutting oil. Overheating is what kills a cobalt bit, and overheating comes from turning slowly and leaning on it.

Cylindrical shank

The shank is cylindrical and the same diameter as the flutes. It fits any standard chuck - a pillar drill, a mains drill, or a cordless driver with a chuck.

Technical specifications

Questions and Answers