Drill bit sizes

Choosing the right drill bit size is essential when drilling into tough materials like stainless steel, hardened steel, or cast iron. Below you’ll find our complete drill bit size listings in both metric and imperial. All TTP HARD drill bits are made from 5% cobalt (M35 grade), SGS-tested for hardness, and trusted by mechanics, engineers, and contractors across Europe. Whether you need a single 6mm bit or a full set, we’ve got the exact sizes for your job.

Drill bit dimensions not only vary in diameter but in length also. Furthermore there are a number of different scales used for measuring the diameter. They include Metric, Imperial, Wire No./Letter and Decimal.

Drill bit size chart

If you need to see how drill bits sizes compare in the different measurement scales we have a link to a Drill bit size chart / drill bit comparison chart

Drill bit tap size chart

If you need to know which drill bit to use for a tap follow link to Drill bit tap size chart

TTP HARD drills are available in both metric and imperial sizes. See below :

Our drill bit size options include both metric and imperial
Our drill bit dimensions (overall drill bit length, flute length, diameter and angle point) for each drill bit size in metric and imperial

Nathan Holle review 300 x 400 px - Drill bit sizes

nathan video image 500 x 300 - Drill bit sizes

Tested & Trusted

“All TTP HARD cobalt drill bits are SGS-tested to Rockwell hardness 66 for proven durability when drilling hardened steel.”

1.TTP HARD drill bit sizes

Metric sizes

TTP HARD DRILL KITS Cobalt Metric drill kits Metric Drill Bits e1538749801739 - Drill bit sizes

Metric drill bit sets

19 piece drill bit set (1mm to 10mm x 0.5mm)

25 piece drill bit set (1mm to 13mm x 0.5mm)

TTP HARD53x10 10x5.3mm TTP HARD Cobalt drill bits Metric drill bits e1538749583140 - Drill bit sizes

Metric packs of 10 drill bits

1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.3mm, 3.5mm, 4mm, 4.2mm, 4.5mm, 5mm, 5.3mm, 5.5mm, 6mm, 6.5mm, 6.8mm

TTP HARD130 1x13mm TTP HARD Cobalt drill bit Metric drill bits e1538748315899 - Drill bit sizes

Metric single drill bits

7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, 10mm, 10.2mm, 10.5mm, 11mm, 11.5mm, 12mm, 12.5mm, 13mm

👉 Looking for the full range? See our Metric cobalt drill bits and sets.

Imperial Sizes

TTP HARD DRILL KITS Cobalt Imperial drill kits Imperial drill bits e1538754841940 - Drill bit sizes

Imperial drill bit sets

21 piece drill bit set (1/16″ to 3/8″ x 1/64″)

29 piece drill bit set (1/16″ to 1/2″ x 1/64″)

TTP HARD1364x10 10x136422 TTP HARD Cobalt drill bits Imperial drill bits e1538754228829 - Drill bit sizes

Imperial packs of 10 drill bits

1/16″, 5/64″, 3/32″, 7/64″, 1/8″, 9/64″, 5/32″, 11/64″, 3/16″, 13/64″, 7/32″, 15/64″, 1/4″

TTP HARD3 8 1x3 822 TTP HARD Cobalt drill bit 326x489 copy - Drill bit sizes

Imperial single drill bits

17/64″, 9/32″, 19/64″, 5/16″, 21/64″, 11/32″, 23/64″, 3/8″, 25/64″, 13/32″, 27/64″, 7/16″, 29/64″, 15/32″, 31/64″, 1/2″

👉 Need inch sizes? Explore our Imperial cobalt drill bits and drill sets

2. TTP HARD drill bit dimensions

metric / imperial

Check Out Best Drill Bit Sets For Metal

Various drill bit sizes for drilling hard metal - Drill bit sizes

FAQ’s

What drill bit sizes are most commonly used in metalworking?

Small pilot sizes (1–5mm / 1/16″–1/8″) are frequently used for starting holes, while larger sizes (10–13mm / 3/8″–1/2″) are used for final cuts.

Do cobalt drill bits come in both metric and imperial sizes?

Yes. TTP HARD cobalt drill bits are available in both metric (1mm–13mm) and imperial (1/16″–1/2″), individually or as complete sets.

Can I buy individual cobalt drill bit sizes?

Yes. Every size is available individually, in packs of 10, or in full sets — giving you flexibility depending on your needs.

Which drill bit size should I use for stainless steel?

Start with a smaller pilot hole (around 3–4mm / 1/8″), then step up to your required size. Using cobalt drill bits with CUT-IT cutting paste ensures cleaner holes and longer bit life.