Torx Bit Sizes: T6 to T40 for Your Projects
By Drill Hog® | Published: 2026-10-19
Category: How-to Guides
Learn how to identify and choose the right Torx bit size for your project, from small T6 electronics bits to large T40 automotive fasteners.
Quick answer
Torx bits range from T6 (smallest, used in electronics) to T40 (largest common size, found in automotive and heavy equipment). Choosing the correct size prevents cam-out and stripping.
Why size matters in Torx bits
Torx bits have a six-point star shape designed to transfer torque without cam-out. Using the wrong size—too small or too large—will cause the bit to slip, rounding the fastener head or damaging the bit. Unlike Phillips or slotted drives, Torx sizes are not interchangeable; a T8 bit will not fit a T9 fastener.
The size number corresponds to the distance across opposite points of the star. Smaller numbers (T6, T8, T9) are common in electronics, appliances, and small hardware. Mid-range sizes (T10, T15, T20, T25) dominate automotive interior trim and general assembly. Larger sizes (T30, T27, T40) handle higher torque loads in suspension, drivetrain, and structural fasteners.
Drill Hog® Hi-Molybdenum Super M7+ bits are impact rated and have a melting point of 4,753°F. That high heat resistance helps prevent bit softening during prolonged impact driver use, especially on stubborn fasteners. The 1/4" hex shank fits all standard impact and drill drivers.
How to choose the right Torx bit size
- Check the fastener head for a printed size number: Most Torx fasteners have the size stamped on the head (e.g., T20, T25). If the number is worn or hidden, look at the fastener packaging or manufacturer spec sheet. Never guess the size—using a bit that is even one size off will cause slipping and damage.
- Match the bit to the fastener without forcing: Insert the bit into the fastener head. It should seat fully and snugly with no wiggle. If it wobbles, the bit is too small. If it won't enter, the bit is too large. A loose fit invites cam-out and stripped heads; a tight fit means you have the wrong size.
- Use an impact-rated bit for high-torque applications: For automotive or heavy equipment, choose a bit like the Drill Hog® Hi-Molybdenum Super M7+ series, which is impact rated and withstands high heat from impact drivers. Standard bits can snap or wear quickly under impact driver torque; an impact-rated bit lasts longer.
- Keep a set of common sizes in your toolbox: Stock bits for the sizes you use most often (e.g., T6, T8, T9, T15, T20, T25, T30, T40). A 10-pack of small sizes like T6 or T8 ensures you have a spare when one breaks or dulls. A missing bit in the middle of a job can stop progress.
Torx bits we recommend
- T-6 Torx Bit T-6 Star Insert Bit T-6 x 1 Hi-Molybdenum M7 Drill Hog® 10 Pack: T-6 Torx Bit Hi-Molybdenum Super M7+ 10 Pack, 1" long, impact rated. The T6 size is ideal for small electronics and precision fasteners; the high-molybdenum alloy adds durability when used in impact drivers.
T-6 Torx Bit T-6 Star Insert Bit T-6 x 1 Hi-Molybdenum M7 Drill Hog® 10 Pack - T-8 Torx Bit Hi-Molybdenum Super M7+ Drill Hog® 10 Pack: T-8 Torx Bit Hi-Molybdenum Super M7+ 10 Pack, 1" long, impact rated. T8 bits are common in automotive interior screws and appliance repair; the 10-pack ensures you always have a spare when one wears out.
T-8 Torx Bit Hi-Molybdenum Super M7+ Drill Hog® 10 Pack - T-9 Torx Bit Hi-Molybdenum Super M7+ Drill Hog® 10 Pack: T-9 Torx Bit Hi-Molybdenum Super M7+ 10 Pack, 1" long, impact rated. T9 is less common but appears in some power tools and electronics; having a dedicated T9 bit avoids the temptation to force a T8 or T10.
