Comprehensive Guide on How to Read Screwdriver Bit Specifications

Choosing the right screwdriver bit not only boosts work efficiency and speeds up screwdriving, but also protects your equipment and prevents surface scratches or stripped screw heads. However, with hundreds of screwdriver bit types on the market, how can you select the exact one you need?

The article below provides a detailed guide on how to read the specifications of common screwdriver bits, helping you easily understand the technical parameters and accurately communicate your requirements to your supplier.

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I. Understanding the Basic Components of a Screwdriver Bit

Before going into detail, please refer to the illustration of the basic structure of a screwdriver bit below:

In the image above, there are two main parts that determine the selection of a screwdriver bit:
👉 E (Tip / Drive End): The part that makes direct contact with the screw.
👉 F (Shank / Drive End): The part that connects (fits) into a power screwdriver, electric screwdriver, or hand driver.

Specific classification:
✔ Tip E comes in a wide variety of shapes to match different screw heads on the market: Phillips (+), slotted (-), Torx, star, hex, nut setter…
✔ Shank F typically comes in 4 most common standards to fit into power tools:
    • A: 5mm hex shank
    • B: 6.35mm hex shank (The most common standard today)
    • C: Ø4 round shank
    • D: Ø5 round shank

💡 Quick tip: If you are unsure which shank F fits your workshop's electric screwdrivers, contact us now for free technical consultation!

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II. Detailed Guide on How to Read Specifications for Each Type of Screwdriver Bit

1. How to read Phillips (+) screwdriver bit specifications

This is the most widely used type of screwdriver bit in mechanical and electronics assembly. The parameters are defined as follows:

• P: Specification symbol (point size) of the Phillips tip. Available standards include: #00, #0, #1, #2, #3…
• d: Diameter of the reduced neck section (mm).
• l: Length of the reduced neck section (mm).
• L: Overall length of the screwdriver bit (mm).

Standard P tip size chart:

P Code	Actual Size (mm)
00#	0.8 ~ 0.9
0#	0.9 ~ 1.0
1#	1.3 ~ 1.4
2#	2.2 ~ 2.3
3#	3.8 ~ 4.0

🎯 Standard reading formula: F x P x d x l x L

Practical example: When you request type Ax1x2x20x40, we will supply the exact specification: 5mm hex shank (A), Phillips #1 tip, 2mm reduced shank diameter, 20mm reduced shank length, and 40mm overall screwdriver bit length.

2. How to read slotted (flat-head) screwdriver bit specifications

For slotted screwdriver bits, the shank parameters remain the same; only the tip dimensions change:

• W: Blade width (mm).
• t: Blade thickness (mm).
• l: Reduced shank length (mm).
• L: Overall screwdriver bit length (mm).

🎯 How to read: W x t x l x L

3. How to read star / Torx screwdriver bit specifications

Torx screwdriver bits are especially common in electronics, automotive, and motorcycle assembly due to their ability to withstand high torque without stripping the screw head.

• T: Symbol for the star-shaped tip (commonly referred to as TA, where A is the size dimension).
• d: Reduced shank diameter (mm).
• l: Reduced shank length (mm).
• L: Overall screwdriver bit length (mm).

Reference table for star tip size codes (TA):

TA Code	Dimension A (mm)
T7	1.956
T8	2.286
T9	2.464
T10	2.718
T15	3.251
T20	3.835
T25	4.394
T27	4.953
T30	5.486
T40	6.604

4. How to read hex (Allen) screwdriver bit specifications

Specifically designed for fastening and removing hex socket bolts and screws.

• H (Hex): Across-flats dimension of the hexagon (distance between two opposite sides), in mm.
• L: Overall screwdriver bit length (mm).

5. How to read bolt nut setter (External Hex / Socket) specifications

Hex nut setters are essential accessories for fastening external hex nuts and bolts.

• A/F (Across Flats): Distance across opposite flats of the hexagon (matching the required wrench/socket size), in mm.
• D: Outer diameter of the nut setter (mm). (Especially important when fastening in tight spaces).
• d: Socket depth of the nut setter (mm).
• L: Overall length of the nut setter (mm).

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