What are the common Torx bit sizes, and what is a nut setter? T10 to T55, Torx vs star vs E-Torx vs hex, Phillips and slotted bits, impact-rated bits, nut setters vs nut drivers, magnetic bit holders, and what to use when the right bit is missing
The Torx sizes you meet on a jobsite are T10, T15, T20, T25, T30 and T40: T20 and T25 drive most deck, trim and cabinet screws, T25 is the roofing and siding screw size, T30 and T40 show up on metal roofing and equipment. A star bit is a Torx bit under a generic name; E-Torx is the external version (a socket that fits a star-shaped bolt head); hex (Allen) is a plain six-sided recess and is not interchangeable. A nut setter is a 1/4 inch hex-shank socket for a drill or impact driver that drives hex-head screws (1/4, 5/16 and 3/8 inch are the roofing and metal-building sizes); a nut driver is the same socket on a screwdriver handle. A magnetic bit holder extends a 1 inch bit and holds the screw on it.
C&R Torx Screwdriver Bits, 4 sizesThe product data lists the C&R Torx bits in T-10, T-20, T-25 and T-30, 100 per tubWhy bits are sold by the hundred. A roofing or siding crew drives thousands of hex-head and Torx screws a week and a bit is a consumable: the tip rounds, the magnet weakens, the bit is dropped off the roof. The questions below are the ones that come up when the right bit is not in the pouch — what the common sizes are, why there is no size between T15 and T20, what a nut setter is and how it differs from a nut driver, which bits survive an impact driver, what to use instead of a Torx bit and what a bit holder does — followed by the bits, setters and holders we stock in tubes and tubs.
Torx bits, nut setters and holders, question by question
Torx point-to-point dimensions are the published series values; the roofing screw head sizes are the ones printed on the fastener boxes.
Bits and setters in plain words
- Common Torx: T10, T15, T20, T25, T30, T40. T25 drives most roofing and siding screws; T20 most deck screws.
- Star bit = Torx bit. E-Torx is the external socket form and does not interchange. Hex is a different drive.
- There is no size between T15 and T20; the series is uneven, so a near size strips the recess.
- Nut setter: hex socket on a 1/4 inch hex shank for a drill. Nut driver: the same socket on a handle. Roofing screw heads are 1/4, 5/16 and 3/8 inch.
- Magnetic setters hold the screw; non-magnetic for stainless screws and clean finishes.
- Impact-rated bits are tougher, not harder; they have a torsion zone and survive an impact driver.
- Phillips #2 is the standard size; slotted bits are called flat bits.
- A magnetic bit holder extends and magnetizes a 1 inch bit; a sliding guide holds the screw straight to start.
Questions people ask
What are the most common Torx bit sizes?
T10, T15, T20, T25, T30 and T40 in construction; T25 is the roofing and siding screw size and T20 the common deck screw.
Why is it called a Torx?
It is the brand name the six-lobed drive was introduced under in 1967, designed to take torque without cam-out.
What is the difference between Torx and E Torx?
Torx is the internal recess driven by a T bit; E-Torx is an external star head driven by an E socket. They do not interchange.
Is there a Torx size between 15 and 20?
No; the series steps from T15 (3.27 mm) to T20 (3.86 mm).
What can I use instead of a Torx screwdriver?
Nothing that will not strip the recess; a flat blade across two lobes turns it once. Keep a tub of the right bits.
How do you unscrew a Torx screw without Torx?
A flat blade or an undersized hex key tapped in will turn it once; a rubber band adds grip; expect to strip it.
What are the dimensions of a T30 Torx bit?
5.52 mm (0.217 inch) point to point on a 1/4 inch hex shank.
What are the hardest screwdriver bits?
Solid carbide and hard S2 steel; but impact drivers want tough, torsion-zone bits, not the hardest ones.
Is there a difference between a star bit and a Torx bit?
No; star is the generic name for the Torx drive.
What are the different sizes of screwdriver bits?
Phillips #0 to #4, slotted by blade width, square #1 to #3, Torx T1 to T100, hex by inch and mm, on 1/4 inch hex shanks in 1, 2, 3-1/2 and 6 inch lengths.
What is the difference between a nut setter and a nut driver?
A nut setter has a 1/4 inch hex shank for a power driver; a nut driver is the same socket on a hand handle.
What can you use instead of a nut driver?
A socket and ratchet, a nut setter in a drill, a box wrench, or locking pliers once.
What are flat screwdriver bits called?
Slotted, flat or straight bits, sized by blade width.
What is a magnetic bit holder for?
It extends a 1 inch insert bit, lets bits swap fast and magnetizes the bit so the screw stays on it.
What is the difference between Torx and hex?
Hex is a six-sided recess; Torx is six-lobed. A hex key in a Torx recess strips it.
What are the dimensions of a T10 Torx bit?
2.74 mm (0.108 inch) point to point.
What can I use instead of a T55 Torx bit?
A 5/16 inch hex key is the usual misfit and will damage the recess; T55 bits come on 5/16 or 1/2 inch drive and are worth buying.
Are there two different types of Torx bits?
Standard Torx and Torx Plus (squarer lobes), plus security Torx with a center hole; E-Torx is the external socket form.
The ratings, test results and standards shown here are the manufacturers' published values, reproduced as published. Nothing on this page is a recommendation by Bayshore Safety that any product is suitable for a particular task, hazard or workplace. Selecting safety products and protective equipment is the responsibility of the end user and the employer, based on their own hazard assessment and the regulations that apply to their work. Confirm every value on the manufacturer's own documentation before use.