T40 refers to the Torx drive size—the six-point star pattern that fits a T40 screw head. It doesn’t describe the bit’s length or shank style. On this page you’ll find T40 bits in different formats to match your tool and task.

• Shank: Most T40 bits use a 1/4-inch hex shank for drill/drivers and bit holders. Some are bit sockets for ratchets.
• Lengths: Options commonly include short (about 1–2.5 in.), medium (3–4 in.), and extra-long (6 in.+) for deep recesses.
• Types: Standard T40 and security T40 (with a center hole) for tamper-resistant screws.

If your screw has a center pin, choose a security T40. When in doubt, a multi-size Torx set (T5–T40) can help you confirm the right fit.

People often say “star bit” when they mean Torx. Torx is a specific six-point star drive system identified by T sizes (like T40). There are also star-like drives that aren’t Torx, so it’s helpful to double-check what you have.

• Torx (6-point): The common star pattern. Labeled T5–T40 and beyond.
• Security Torx: Same 6-point shape, but the bit has a center hole to fit screws with a center pin.
• Other stars: Some 5-point or specialty stars look similar but won’t match Torx sizes.

To avoid stripping, match the bit to the exact screw style and size. If your fastener is stamped with a T size, you’re working with Torx.

T40 describes the drive size in the screw head, not the bolt’s diameter or thread. There isn’t a universal bolt size for T40; manufacturers use Torx drives across different bolt sizes in automotive, appliance, and home projects.

• Check markings: Some fasteners are labeled with the Torx size (e.g., T40).
• Test-fit gently: A T40 bit should seat fully with minimal wiggle. If it cams out, switch sizes.
• Use the right type: If there’s a center pin in the screw head, choose a security T40 bit with a hole.
• Avoid force: Apply straight, steady pressure and moderate torque to reduce stripping.

A Torx bit set (T5–T40) can help you quickly confirm the best fit on mixed fasteners.

For safety and a clean result, it’s best to use the correct Torx bit. Improvised tools may slip, damage the fastener, or injure you. If you don’t have one on hand, these options can help:

• Pick up a bit or set: Order a Torx or security Torx bit (if your screw has a center pin) for pickup or delivery.
• Use a hand driver: Pair the right bit with a manual handle for more control on delicate tasks.
• Free a stuck screw first: Consider a penetrating lubricant and proper bit engagement rather than extra force.

Using flathead or hex drivers as substitutes is generally not recommended, as it can strip the screw head.

Yes, many T40 bits are designed for drill/drivers. Look for a 1/4-inch hex shank, which fits most chucks and bit holders. If you’re using an impact driver, choose impact-rated bits for durability.

• Choose the right length: Short bits (about 1–2.5 in.) offer better control; long bits (4–6+ in.) reach into deep recesses.
• Magnetic tips: These can help hold the screw for easier starts.
• Speed and pressure: Use moderate speed and firm, in-line pressure to reduce cam-out.
• Security screws: If the screw has a center pin, use a security T40 bit with a hole.

Always match the bit style and size to the fastener to help prevent damage.