Drill Shank Types Explained: Round, Hex, SDS-Plus and SDS-Max - A Complete Guide

What a Drill Shank Actually Does

The drill shank is the non-cutting end of the bit that fits into the chuck or tool holder. It is the mechanical interface that carries the entire torque and impact load from the drill to the cutter. A shank that does not match the tool holder will slip, spin, or fail under load.

The hidden work of the shank is visible when you compare these numbers with what happens on site. The shank controls the amount of rotational force that reaches the cutting edges. It also determines whether a rotary hammer can transfer hammer blows into the bit. That is why a round shank bit in an SDS hammer does nothing except spin.

The Four Drill Shank Types You'll Meet in Procurement

Every drill shank type exists for one reason: to deliver torque under specific drilling conditions. When procurement teams understand the four standard families, they stop wasting money on bits that cannot be used at all.

Round shank

The round shank is the generic workhorse. It is made to the DIN 338 standard with a diameter tolerance of h7, and it relies on the chuck's friction grip to hold the bit. It is perfect for metal drilling, wood, and light masonry in portable drills and drill presses. The tradeoff is low torque capacity and no impact transfer.

Hex shank

The hex shank has six flat faces that engage positively with a hex chuck or quick-change driver. The 1/4 inch size is common in multi-bit kits. It gives more torque than a round shank and is easy to swap between bits, but it cannot take heavy hammer blows.

SDS-Plus shank

The SDS-Plus shank follows ISO 7435. It has two open slots and two closed grooves that lock into the hammer with a bayonet action. This allows the bit to slide forward and back while rotating, which transfers impact energy without deformation. It suits concrete and masonry holes from 12mm to 26mm.

SDS-Max shank

The SDS-Max shank is a larger version of the same system, with a shank diameter around 18mm. It is designed for heavy rotary hammers and drilling holes above 26mm in concrete and rock. The larger cross-section absorbs the shock loads of high-performance hammers.

How to Match Drill Shank Types to Your Drilling Jobs

The matching rule is simple: check your tool holder first, then the material, then the hole diameter. If you follow this order, you will never order a useless bit again.

The chart below plots the relative torque capacity of the four shank families. The data comes from tool holder performance comparisons used in our own machining tests at Zhejiang URUS Tools Co., Ltd.

This is why a procurement manager needs to ask one question before buying a hundred SDS-Plus bits: does the drill have an SDS-Plus holding mechanism? Understanding how force is transmitted is also covered in these drilling basics, which explain the tool side of the equation.

The four-step shank selection process

1. Open the tool holder and read its brand and size marking. A keyless chuck needs a round shank; a quick-change cap needs hex; a rotary hammer needs SDS-Plus or SDS-Max.
2. Confirm the material. Concrete and masonry are for SDS shanks. Metal and wood are for round or hex shanks.
3. Estimate the hole depth and diameter. If the hole goes beyond 26mm in concrete, switch to SDS-Max.
4. Check the maximum chuck capacity on the tool. If the shank is larger than the chuck opening, the bit will not seat.

What B2B Buyers Should Check Before Ordering Drill Shank Types

At Zhejiang URUS Tools Co., Ltd. in Jiashan, we run a fixed incoming check on every shank sample. The five acceptance points are shank diameter, hardness, surface condition, shank geometry, and packaging identification.

The first and most common failure is a shank that is slightly smaller than the standard. A round shank with a diameter tolerance of h7 should measure within a few hundredths of a millimeter. Use a micrometer to verify the axis. Our 65,000 square meter facility in Jiashan has the equipment to measure these tolerances in-house.

SDS-Plus Hammer Drill Bit for Concrete and Stone DrillingThis SDS hammer drill bit features an SDS-Plus shank, ideal for 12-26mm concrete anchors, and is available with milled flute options for efficient drilling in brick, concrete, and stone.View Product →

For concrete drilling, the SDS-Plus shank is the first family to verify. If your crew uses 12mm to 26mm concrete anchors, an SDS-Hammer Drill Bit with an SDS-Plus shank is the safest starting point.

SDS-Max Hammer Drill Bit for Heavy Rotary Hammer ApplicationsDesigned for large holes in concrete and masonry, this SDS-Max drill bit has an optimized flute for efficient power transfer, suitable for high-performance rotary hammers.View Product →

When the job moves to heavy rotary hammers and large holes, upgrade to an SDS-Max shank. The larger shank cross-section tolerates the shock waves of high-performance hammers without deformation.

Split Point Drill Bit with Self-Centering Tip for MetalThe split point tip self-centers to reduce walking, making it a reliable choice for portable drills when drilling metal, ensuring accurate hole placement.View Product →

For metal drilling in portable drills, a split point shank is the reliable choice. The split point self-centers and reduces walking, which is especially important in manual drilling where a sloppy start ruins the hole.

• Diameter tolerance: verify against DIN 338 for round shank or ISO 7435 for SDS shank.
• Hardness: a shank should test between HRC 42 and HRC 48.
• Surface condition: no burrs, no rust, no coating defects on the shank.
• Shank geometry: slots and grooves must be clean, with no deformation from heat treatment.
• Packaging: the label must clearly state the shank type and diameter in millimeters.

Common Shank Mismatches and How to Prevent Them

Three mismatch patterns cause most drill failures on construction sites: using a round shank in an SDS tool, forcing an SDS-Max shank into an SDS-Plus chuck, and running an undersized hex shank under high torque.

• Round shank in an SDS hammer. The locking mechanism is not engaged, so the tool spins without impact. The bit heats up and the shank becomes polished, which ruins it for any future chuck use.
• SDS-Max shank in an SDS-Plus chuck. The larger shank does not enter the holder. Forcing it damages the grooves and the tool itself.
• Undersized hex shank under load. If the 1/4 inch hex shank is weak or worn, it twists inside the bit holder and the drill stops cutting.

Frequently Asked Questions About Drill Shank Types

What is the most common drill shank type?

The round shank is the most common because it fits the widest range of portable drills and drill presses. In construction and industrial catalogs, SDS-Plus is the second most ordered shank family.

Can I use a round shank bit in an SDS drill?

No. SDS tools require a shank with slots and grooves that engage the hammer lock. A round shank will rotate freely inside the holder and the impact mechanism will not function.

What is the difference between SDS-Plus and SDS-Max?

SDS-Plus has a 10mm shank and handles concrete holes from 12mm to 26mm. SDS-Max has a much larger shank of around 18mm and is used for heavy hammers and holes above 26mm.

What shank type should I order for masonry drilling?

For rotary hammer drilling, order SDS-Plus for standard concrete anchors and SDS-Max for heavy core work. Round shank masonry bits only fit in hammer-action drills that use a keyed chuck.