Drill bits are made with different materials. In order to drill high-strength and hard material drilling process, steel drill bits are used to drill wood. But drilling steel and more hard material will need more hard drill bits. As a solution of this high-speed steel (HSS), drill bits are made. Let’s see what is HSS Drill bit?
HSS drill bits are made by mixing these materials 0.85% C; 4% Cr; 5% Mo; 6% W; 2% V. According to its material mixing proportion, strength has varied. M1, M2, M7, M35, M42, and M50 have different strengths and resistance HSS. HSS is used for drill bits, cutting tools, knives, and many tough tools.
When you use the HSS drill bit you should know its material properties, how to use it?, where to use and many more details. So you can grab all in detail by using the below article. So keep reading on until you find your information.
HSS Bits Used For
HSS drill bits are used to drill soft materials such as aluminum, brass, mild steel, plastic, hardwood, softwood, fiber, etc. Coated HSS bits can be used to drill cast iron and many more tough materials.
In order to increase the performance, HSS bits are coated with Titanium Nitride (TiN), Titanium Carbon Nitride (TiCN), and Titanium Aluminium Nitride (TiAlN). Those will reduce the friction of the drill bit and material as well as increase the heat resistance and durability of the drill bit.
How HSS Drill Bit is Made?
HSS drill bits are made with 0.85% C; 4% Cr; 5% Mo; 6% W; 2% V (M2). The main material is steel. By changing these material proportions, its hardness can be varied. M1, M2, M7, M35, M50, M42 are the strength class of the HSS. Drill bits are made with mostly M2.
| Type | Carbon (%) | Tungsten (%) | Molybdenum (%) | Chromium (%) | Vanadium (%) | Cobalt (%) | Hardness Rockwell C (%) | Term |
| M1 | 0.80 | 1.50 | 8.00 | 4.00 | 1.00 | – | 63-65 | “HSS” |
| M2 | 0.85 | 6.00 | 5.00 | 4.00 | 1.90 | – | 63-65 | “HSS” |
| M7 | 1.00 | 1.75 | 8.75 | 4.00 | 2.00 | – | 63-65 | “HSS” |
| M35 | 0.80 | 6.00 | 5.00 | 4.00 | 2.00 | 5 | 65-67 | 5% Cobalt |
| M42 | 1.10 | 1.50 | 9.50 | 3.75 | 1.15 | 8 | 65-67 | Super Cobalt |
| M50 | 0.85 | 0.10 | 4.25 | 4.00 | 1.00 | – | 63-65 | “HSS” |
| Type | Usage |
| M1 | Use for general purpose |
| M2 | Twist drills, reamers, milling cutters, taps, and dies, broaches, knives, saws, cold work tools |
| M7 | Heavy construction equipment |
| M35 | Use for fast cutting and durable cutting tools |
| M42 | Use for higher cutting speed tools |
| M50 | Use for drill bits, ball bearings |
Properties of High Speed Steel
Density (×1000 kg/m3) – 8.67
Poisson’s Ratio – 0.27-0.30
Elastic Modulus (GPa) – 190-210
Thermal Expansion (10-6/ºC) – 9.7
Thermal Conductivity (W/m-K) – 19.9
Rockwell Hardness – 63-65
The high-Speed Steel drill bit can only drill 2-3 times the drill diameter before pecking. This means when you drill once, you can drill 2-3 times the drill diameter into the material without tool coolant. You have to pull out and then drill again.
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Compared With Other Types of Drill Bits
Steel Drill Bits
HSS drill bits are more strong and hard than steel drill bits. Steel drill bits are used to drill the softwood and some plastics. Steel Drill bits can be overheated when it uses for tough material drilling such as cast iron, concrete, stone, etc.
Cobalt Drill Bits
HSS is less strong than the cobalt drill bits. Cobalt Drill bits are different from HSS with the mixed cobalt percentage. When the cobalt is added 5%, it is called 5% cobalt, and 8% is called super cobalt. These tools are really hard, strong, and heat resistant than regular HSS. So Cobalt drill bits can be run faster and high-speed feeds.
Carbide Drill Bits
Carbide drill bits are more strong than HSS drill bits. Using a carbide drill bit, you can drill more fast and high RPM. Although HSS is coated with some materials, its hardness can’t be compared with the carbide drill bits. It is higher than HSS.
Diamond Drill Bits
Extremely strength than HSS. Diamond drill bits are used for the drilling and cutting of extremely hard materials such as tile, glass, and stone, etc. HSS is not able used instead of these.
How to Sharpen the HSS Drill Bit?
You can sharpen the HSS drill bit when the chipping length is below 0.02,” or drilled holes are out of the tolerance. When the drilling produces more noise is another sign of sharpening. You can use a file or grinder made with carbide or diamond. The cutting angle should maintain according to the material requirement.
| Workpiece Material | Point Angle | Helix Angle | Lip Relief Angle |
|---|---|---|---|
| Aluminum | 90 to 135 | 32 to 48 | 12 to 26 |
| Brass | 90 to 118 | 0 to 20 | 12 to 26 |
| Cast iron | 90 to 118 | 24 to 32 | 7 to 20 |
| Mild Steel | 118 to 135 | 24 to 32 | 7 to 24 |
| Stainless Steel | 118 to 135 | 24 to 32 | 7 to 24 |
| Plastics | 60 to 90 | 0 to 20 | 12 to 26 |
Read More About – 26 Types Drill Bits for – Metal | Wood | Stone | Concrete
Usage and Cutting Speed?
HSS drill bits are used to drill mild steel, cast iron, softwood, plastic, hardwood, fiber, and many soft materials. You can use a 118-degree angle for soft material drilling such as aluminum, softwood etc. And 135-degree for the hard material drilling such as cast iron using the HSS drill bits.
| Material | Recommended speed (SFM) |
| Aluminum and its Alloys | 200-300 |
| Brass and Bronze (Ordinary) | 150-300 |
| Bronze (High Tensile) | 70-150 |
| Die Casting (Zinc Base) | 300-400 |
| Iron-Cast (Soft) Cast (Medium Hard) Hard Chilled Malleable | 75-125 50-100 10-20 80-90 |
| Magnesium and its Alloys | 250-400 |
| Monel Metal or High-Nickel Steel, Stainless Steel | 30-50 |
| Plastics or Similar Materials | 100-300 |
| Steel Mild .2 Carbon to .3 Carbon Steel .4 Carbon to .5 Carbon Tool 1.2 Carbon Forgings Alloy – 300 to 400 Brinell | 80-110 70-80 50-60 40-50 20-30 |
You can calculate RPM using the SFM as below,
R.P.M. = (3.8197 / Drill Diameter) x S.F.M.
Read More About – How to Drill Cast Iron? – The Detailed Guide
Conclusion
HSS drill bits are more strong than steel drill bits. Its hardness, strength, and resistance can be varied as below
Steel drill bits < HSS drill bits < Cobalt drill bits < Carbide drill Bits < Diamond drill bits
It can be used for many reasons. Mostly HSS drill bits are used to drill steel.
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