Bosch PRO Metal HSS-G Twist Drill Bit Set, DIN 338, Ø 1-10 mm, 19 pcs, 2608587013

Bosch PRO Metal HSS-G Twist Drill Bit Set for Metal, DIN 338, Ø 1-10 mm, 19 pcs

Bosch PRO Metal HSS-G (order number 2 608 587 013) is a set of 19 twist drill bits for metal covering 1.0 to 10.0 mm in 0.5 mm steps. The bits are made of ground high-speed steel to DIN 338, with a 135° point angle and a split point. The set comes in a plastic ProBox cassette measuring 172 x 115 x 42 mm with marked slots. A set for everyday metalwork: the whole ladder from 1 to 10 mm in one box.

What it is for

Bosch describes the bits as a choice for construction workers and installers. The materials the manufacturer lists are alloyed and unalloyed steel, non-ferrous metals, cast iron, plastics and wood - in practice almost everything drilled on site and in the workshop: sheet metal and profiles, angle iron, tubes, aluminium and brass parts, cast iron, PVC.

The bits run in an ordinary drill or a cordless driver with a three-jaw chuck, with hammer action switched off. Hammer action is for concrete and masonry and chips the cutting edge of a metal bit.

What the "G" in HSS-G means

HSS stands for high-speed steel. The letter G (from the German geschliffen - ground) tells you how the flute was made: on HSS-G bits the flute and the cutting edges are ground out of solid stock, while on cheaper HSS-R bits the flute is rolled. A ground bit has more accurate point geometry and better concentricity - it runs rounder, bites cleaner and produces a hole closer to nominal size. Bosch puts it briefly: "Ground high-speed steel for strength and durability".

The manufacturer also compares it within its own range: this article lasts up to 2x longer than a Bosch PointTeQ drill bit (the rolled HSS-R line of Bosch). That is Bosch's own comparison and refers to the life of the cutting edge, not to drilling speed.

135° split point

The tip is a split point ground at 135°. The chisel edge in the centre is split, which does two things: the bit centres itself instead of wandering across the surface, and it needs less feed pressure to start cutting. Bosch describes it as a "split-point tip for starting holes exactly where you need them", with "no need for pilot holes".

The difference shows on sloped or smooth surfaces - painted sheet metal, a tube, a finished part. An ordinary bit with a 118° point and a solid chisel edge walks off unless centre-punched first; with a 135° split point the punch mark is usually unnecessary.

Shank and chuck

The shank is cylindrical and its diameter equals the drill bit diameter - it is not reduced. That brings one practical limit: the 10 mm bit needs a chuck that opens to at least 10 mm. A 1.5-13 mm chuck takes it, 0.8-10 mm is right at the limit, and in a small 1-6.5 mm chuck the upper diameters will not fit. Because the shank is a plain cylinder, the bits work in a three-jaw chuck of any brand of machine - which is exactly why Bosch prints the Universal brand fit mark on the packaging.

The diameters in the set

The set holds 19 bits, one of each diameter, in 0.5 mm steps across the whole range. Below are the diameters with working and total lengths as published by Bosch:

The working length is the fluted part and sets the maximum material thickness for one pass: 87 mm with the 10 mm bit, 33 mm with the 3 mm one.

The standard tapping drill sizes for metric coarse threads are 2.5 mm for M3, 3.3 for M4, 4.2 for M5, 5.0 for M6, 6.8 for M8 and 8.5 for M10. This set contains 2.5, 5.0 and 8.5 mm, so M3, M6 and M10 are covered; 3.3, 4.2 and 6.8 mm are missing because the step here is 0.5 mm.

Technical specifications

What is in the set

• 19 Bosch PRO Metal HSS-G twist drill bits for metal, one of each diameter: 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5 and 10.0 mm
• Plastic ProBox cassette 172 x 115 x 42 mm with marked slots and a Euro hole for hanging
• No machine - the article is the bit set only
• No cutting oil

Working tips

• Speed goes down as diameter goes up. Small bits want high rpm, large ones low. A 10 mm bit run flat out in steel will overheat its cutting edge in seconds.
• Lubricate in steel. A drop of cutting oil lowers the temperature and multiplies the life of the bit. Cast iron is drilled dry; aluminium wants oil.
• No hammer action. If the machine has a selector, it stays on the drill symbol, not the hammer.
• Keep the feed steady. The bit should cut a chip, not rub. If you get dust instead of a spiral, either the speed is too high or the edge is already blunt.
• Large holes in two steps. For a 10 mm hole, drill 4-5 mm first and open it to size - the load on the chisel edge drops and the hole comes out truer.
• Put each bit back in its slot. The slots are marked by diameter, so a missing size shows at a glance.

Questions and answers