DIN 345 Taper Shank Drill Size Chart: All Diameters, Lengths & MT Sizes

DIN 345 is the German industrial standard that defines the dimensions, tolerances, and Morse Taper assignments for taper shank twist drills. It is the most widely referenced standard for taper shank drills worldwide, used by manufacturers, distributors, and machine shops across Europe, Asia, the Middle East, and South America. If you are buying or specifying taper shank HSS twist drills, DIN 345 is the standard you need to know.

This page provides the complete size chart for all standard DIN 345 diameters from 6 mm to 76 mm, along with practical guidance on how to use the chart for procurement and workshop reference.

What DIN 345 Defines

DIN 345 (full title: Spiralbohrer mit Morsekegel-Schaft — twist drills with Morse Taper shank) specifies the following for each drill diameter:

• Flute length (l1): The length of the helical cutting portion of the drill. This determines the maximum drilling depth.
• Total length (L): The overall length from the tip of the drill to the end of the tang. This determines the minimum clearance required above the workpiece.
• Morse Taper number: Which MT size (MT1 through MT5) is assigned to the drill. This is fixed by the standard and depends on the drill diameter.
• Diameter tolerances: The allowable variation in drill diameter (typically m7 for the cutting diameter).
• Point angle: Standard 118 degrees (some manufacturers offer 130 degrees for specific materials, but 118 degrees is the DIN 345 default).

DIN 345 is harmonized with ISO 296 (the international standard for Morse Taper dimensions) and is functionally equivalent to many national standards worldwide. A DIN 345 drill from a Chinese factory will fit a German machine spindle — the dimensions are universal.

Scope and Diameter Coverage

DIN 345 covers taper shank twist drills from 6 mm to 100 mm in diameter, though the practical range for standard HSS twist drills is 6–76 mm. Sizes above 76 mm are typically only available in carbide-tipped or indexable configurations. The standard provides dimensions for whole-millimeter and half-millimeter increments throughout the range.

Complete DIN 345 Size Chart

The table below lists all commonly manufactured DIN 345 taper shank drill sizes. Dimensions are in millimeters. The Morse Taper assignment follows DIN 228 / ISO 296.

MT1 Range (6–13.8 mm)

MT2 Range (14–23 mm) — Transition at 14 mm

MT3 Range (23.5–31.5 mm) — Transition at ~23.5 mm

MT4 Range (32–50 mm) — Transition at 32 mm

MT5 Range (51–76 mm) — Transition at 51 mm

Notes:

• This table includes the most commonly manufactured sizes. Additional half-millimeter increments exist within each range but may not be stocked by all distributors.
• Total length includes the tang. The distance from the drill point to the beginning of the taper is approximately equal to the flute length plus a short cylindrical section.
• All dimensions are nominal. Manufacturing tolerances per DIN 345 apply.

DIN 1870 Extra-Long Comparison

DIN 1870 defines extra-long taper shank twist drills. These drills use the same Morse Taper assignments as DIN 345 but have significantly longer flutes — approximately 50% longer than the DIN 345 equivalent. The total length increases accordingly.

DIN 1870 drills are used when you need to drill deeper than the standard DIN 345 flute length allows, but the application still requires a taper shank connection for rigidity and torque. Typical applications include drilling through thick structural members, deep anchor holes, and through-holes in large castings.

Important considerations for DIN 1870:

• Longer flutes mean more material removal per revolution and higher chip volume. Use peck drilling cycles (periodic retraction) to clear chips and prevent chip packing in the flutes.
• The longer unsupported length increases deflection. Use lower feed rates and ensure your machine has adequate rigidity for the hole diameter.
• DIN 1870 drills are significantly more expensive than DIN 345 equivalents due to the extra material and longer grinding time. Order them only when the standard length is genuinely insufficient.

How to Read the Chart: Practical Examples

Here are three real-world scenarios showing how to use the DIN 345 size chart for practical drill selection:

Example 1: Drilling a 25 mm hole in a steel plate

Look up 25.0 mm in the chart:

• Flute length: 160 mm — this is the maximum depth you can drill in a single pass.
• Total length: 281 mm — your machine needs at least 281 mm of vertical clearance above the workpiece.
• Morse Taper: MT3 — your machine spindle (or an adapter sleeve) must accept MT3.

If your plate is 30 mm thick, the 160 mm flute length is more than sufficient. If the plate is 180 mm thick, you need a DIN 1870 extra-long drill (240 mm flute) for through-drilling.

Example 2: A customer needs a drill for their MT4 radial drill press

From the chart, MT4 covers diameters from 32 mm to 50 mm. The customer can use any drill in this range directly in their spindle without an adapter. For diameters below 32 mm (e.g., a 20 mm drill, which is MT2), they will need an MT2-to-MT4 taper sleeve.

Example 3: Ordering a set for a new workshop

A new metal fabrication workshop with an MT3 drill press needs a starter set. From the chart, the MT3 native range is 23.5–31.5 mm. They will also need MT1-to-MT3 and MT2-to-MT3 taper sleeves to use smaller drills. A practical starter kit might include:

• MT1 drills: 6, 8, 10, 12 mm (with MT1→MT3 sleeve)
• MT2 drills: 14, 16, 18, 20, 22 mm (with MT2→MT3 sleeve)
• MT3 drills: 24, 25, 26, 28, 30 mm (direct fit)

What to Specify When Ordering

When placing an order for DIN 345 taper shank drills, provide the following information to avoid errors and delays:

1. Drill diameter — in millimeters, to 0.5 mm precision (e.g., "20.0 mm" or "14.5 mm").
2. Standard — specify DIN 345 (standard length) or DIN 1870 (extra long). If you only say "taper shank drill," most suppliers will assume DIN 345.
3. Material grade — specify the HSS grade:
   • M2 (HSS-G): The standard industrial grade. Suitable for mild steel, cast iron, aluminum, and general-purpose metalworking. Best price-performance ratio.
   • M35 (HSS-E / HSS-Co5): Contains 5% cobalt for superior red hardness. Required for stainless steel, alloy steels, and high-temperature alloys. Approximately 30–50% more expensive than M2.
   • M42 (HSS-Co8): 8% cobalt — highest heat resistance but more brittle. For specialized high-speed production on tough materials. Specify only when M35 is insufficient.
4. Surface treatment (optional) — specify if you need a coating:
   • Bright finish (uncoated): Standard for M2 and M35. Lowest cost.
   • Steam oxide (black oxide): Thin oxide layer that reduces friction and improves chip flow. Minimal cost addition.
   • TiN (gold color): Titanium nitride coating increases surface hardness and extends life in steel. Common upgrade for production use.
5. Quantity — taper shank drills are typically sold individually (not in sets) due to the wide price range across diameters. Specify the quantity per diameter.

Zhonghuan manufactures the full range of DIN 345 taper shank HSS twist drills in M2 and M35 grades, with optional TiN and steam oxide coatings. Straight shank HSS drills (DIN 338 / DIN 340) are also available for smaller diameter requirements. Contact us for current pricing and lead times on bulk orders.

Related Procurement Programs

If you are sourcing this product line for a distributor, importer, or private-label channel, these OEM and wholesale programs cover the procurement questions buyers usually ask next.

• HSS Twist Drill Bits Wholesale & OEM Supply for Metalworking Channels — HSS twist drill bit wholesale and OEM supply for importers, industrial distributors, and private-label brands: M2, M35 cobalt, DIN 338, DIN 345, black oxide…
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