When engineers and buyers specify a DIN 333 center drill, one of the most common questions we receive is: "What's the difference between Type A and Type B — and which one do I actually need?"
It's a fair question. Both types share the same 60° chamfer angle, follow the same DIN 333 standard, and are available in the same materials. But there is a meaningful geometric difference between them — one that has a direct impact on how well your center hole holds up through the machining process.
This guide explains the distinction clearly, with DIN 333 dimension tables for both types.
What Is a DIN 333 Center Drill?
A center drill — also called a combined drill and countersink — is used to create a precise 60° conical hole at the end of a workpiece before turning between centers on a lathe. The center hole provides a stable seating point for the tailstock center, ensuring concentricity and positional accuracy throughout subsequent turning, grinding, or milling operations.
DIN 333 is the German standard (Deutsches Institut für Normung) that governs the geometry, dimensions, and tolerances of 60° center drills. It defines three types: Type A, Type B, and Type R. This article focuses on the two most commonly specified types: A and B.
The Core Difference: One Chamfer vs. Two
Quick Reference: Type A vs. Type B
| Type A (DIN 333-A) | Type B (DIN 333-B) | |
| Chamfer geometry | Single 60° chamfer | 60° chamfer + 120° protection |
| Hole mouth protection | None | Yes — 120° guards the entry |
| Body diameter (d2) | Smaller | Larger (for same d1) |
| Overall length (L1) | Shorter | Longer |
| Best for | General turning, immediate use | Multi-op, storage between stages |
| Precision requirement | Standard | Higher — protected seating surface |
| Material options | M2, M35 | M2, M35 |
| Surface finish | Bright / TiN | Bright / TiN |
DIN 333 Type A — Standard Dimensions
| d1 — Pilot dia. (mm) | d2 — Body dia. (mm) | L1 — Overall length (mm) |
| 1.00 | 3.15 | 31.5 |
| 1.25 | 3.15 | 31.5 |
| 1.60 | 4.00 | 35.5 |
| 2.00 | 5.00 | 40.0 |
| 2.50 | 6.30 | 45.0 |
| 3.15 | 8.00 | 50.0 |
| 4.00 | 10.00 | 56.0 |
| 5.00 | 12.50 | 63.0 |
| 6.30 | 16.00 | 71.0 |
| 8.00 | 20.00 | 80.0 |
| 10.00 | 25.00 | 100.0 |
| 12.50 | 31.50 | 125.0 |
DIN 333 Type B — Standard Dimensions
| d1 — Pilot dia. (mm) | d2 — Body dia. (mm) | L1 — Overall length (mm) |
| 1.00 | 4.00 | 35.5 |
| 1.25 | 5.00 | 40.0 |
| 1.60 | 6.30 | 45.0 |
| 2.00 | 8.00 | 50.0 |
| 2.50 | 10.00 | 56.0 |
| 3.15 | 11.20 | 60.0 |
| 4.00 | 14.00 | 67.0 |
| 5.00 | 18.00 | 75.0 |
| 6.30 | 20.00 | 80.0 |
Material Options: M2 vs. M35
Both Type A and Type B center drills are available in two HSS grades. The choice of material is independent of the type — it depends on the workpiece material and production volume.
M2 HSS — Standard Grade
M2 (HS6-5-2) is the most widely used HSS grade globally. It offers good toughness, reliable wear resistance, and consistent performance across a broad range of workpiece materials — mild steel, aluminum, cast iron, copper, and most non-ferrous metals. M2 center drills are the standard choice for general machining environments.
M35 HSS-Co — Cobalt Grade for Demanding Applications
M35 (HS6-5-2-5, also known as HSSCo5) adds 5% cobalt to the M2 base. This raises heat resistance to approximately 630–650°C and increases hardness to 63–66 HRC. M35 is the preferred grade when centering stainless steel, alloy steel, or other difficult-to-machine materials, or in high-volume production where tool life is a priority.
Surface Finish Options
How to Choose: A Practical Decision Guide
If you are centering a workpiece that will be turned immediately in the same setup, Type A is the right choice. It is simpler, slightly shorter, and covers the majority of standard lathe centering applications.
If your process involves any of the following, specify Type B:
• The workpiece moves between machines or shifts between operations
• Parts are stored or handled after centering and before final turning
• Your tolerances require consistent, repeatable center hole geometry across a production run
• You are working with precision shafts where runout from a damaged center hole is not acceptable
When in doubt, Type B is the safer specification. The additional protection chamfer adds no complexity to the drilling operation itself — it simply ensures that the seating surface remains intact.
What Jiacheng Tools Offers
At Jiacheng Tools, we manufacture DIN 333 center drills in both Type A and Type B, available in M2 and M35 materials with bright or TiN coating. All center drills are 100% full ground from solid bar stock, with body tolerance h7, across pilot diameters from 1.00mm to 12.50mm (Type A) and 1.00mm to 6.30mm (Type B).
OEM and private label supply is available. We work with distributors worldwide across automotive, aerospace, general engineering, and tooling supply sectors. If you need to confirm a specification, request a sample, or discuss a custom size range, contact our team at joeyzhu@jiachengtoolsco.com or visit www.jiachengtoolsco.com.
Post time: Apr-29-2026