ToolsArmenia Knowledge BaseDifferences Between SDS Plus, SDS Max, and HEX Systems SDS Plus, SDS Max, and HEX fastening systems are designed for different classes of drilling and demolition work. This guide explains their construction, applications, compatibility, and the main criteria for choosing the correct system. Reading time: about 15 minutesUpdated: July 2026ToolsArmenia Editorial Team Table of Contents What an accessory system is What SDS Plus is What SDS Max is What HEX is System comparison Compatibility and adapters 5 selection steps Common mistakes Frequently asked questions What Is an Accessory Fastening System? A fastening system is the connection between a tool’s chuck and the shank of its working accessory. It determines which drill bit, core bit, point, or chisel can be installed and how motor rotation and impact energy are transferred to the accessory. With SDS and HEX systems, the accessory is generally installed without a conventional three-jaw chuck. Grooves or flat faces on the shank provide retention, torque transfer, and, in applicable systems, the axial movement needed for hammer action. Main ruleTool power or impact energy does not determine accessory compatibility. Always verify the chuck system and the exact shank size first. What Is SDS Plus? SDS Plus is one of the most common fastening systems for light and medium rotary hammers. The nominal shank diameter of an SDS Plus accessory is generally 10 mm. Its grooves allow fast insertion, secure retention, and limited axial movement during hammer operation. Typical toolsLight and medium rotary hammers for drilling concrete and limited chiselling work. Typical accessoriesSDS Plus drill bits, small and medium core bits, pointed and flat chisels, and other compatible accessories. AdvantagesLow tool weight, quick accessory changes, wide availability, and good control in everyday installation work. LimitationsNot intended for very large drill bits, heavy core bits, or prolonged intensive demolition. SDS Plus is suitable for anchor holes, fastener installation, small openings for utilities, limited tile removal, and light renovation. What Is SDS Max? SDS Max is intended for heavier and more powerful rotary hammers. The nominal shank diameter of an SDS Max accessory is generally 18 mm. Its larger shank and fastening geometry are designed to transmit higher impact and rotational loads. Typical toolsHeavy rotary and combination hammers for large-diameter drilling and demolition. Typical accessoriesSDS Max drill bits, large core bits, breakthrough bits, points, flat chisels, and spade chisels. AdvantagesHigh-load transfer, larger drilling capacities, and efficient work in hard concrete. LimitationsTools and accessories are heavier and more expensive and can be inconvenient for small, precise holes. SDS Max is suitable for deep and large holes, heavy core-bit work, channel cutting, wall and floor demolition, and prolonged professional use. What Is a HEX System? HEX is a general description for a fastening system with a hexagonal shank. It is widely used in demolition hammers, points, chisels, and some specialised tools. The hexagonal form mechanically transmits high impact loads and prevents the accessory from rotating inside the holder. HEX is not one universal sizeHexagonal shanks of 17, 19, 28, 30 mm, and other sizes may belong to different systems. A HEX marking alone does not guarantee compatibility with every HEX tool. Typical toolsElectric and pneumatic demolition hammers and specialised impact equipment. Typical accessoriesBull points, flat chisels, wide spades, asphalt cutters, and specialised demolition accessories. AdvantagesSimple, durable construction and the ability to transmit high impact loads. LimitationsMultiple sizes and locking designs, limited interchangeability, and often an impact-only operating mode. When choosing HEX, check the hex size, total shank length, locking groove or collar position, and the manufacturer’s compatibility information. SDS Plus, SDS Max, and HEX Compared CriterionSDS PlusSDS MaxHEX ShankUsually 10 mm with grooves.Usually 18 mm with larger grooves.Hexagonal, with different sizes and locking designs. Tool classLight and medium rotary hammers.Heavy rotary and combination hammers.Primarily demolition hammers and specialised equipment. Main workSmall and medium holes and light chiselling.Large holes, core bits, heavy drilling, and demolition.Intensive breaking, chiselling, and material removal. Weight and controlLighter and easier to control.Heavier but more productive in demanding work.Depends on size; tools are often heavy and demolition-focused. Typical accessoriesDrill bits, small core bits, and light chisels.Large drill bits, core bits, chisels, and spades.Points, chisels, spades, and specialised accessories. InterchangeabilityNot directly compatible with SDS Max.Not directly compatible with SDS Plus.Exact size and locking geometry must match. Quick selectionSDS Plus for everyday drilling and light chiselling. SDS Max for large diameters and heavy work. HEX mainly for intensive demolition, with mandatory verification of the exact size. Compatibility, Adapters, and Limitations An SDS Plus accessory does not fit directly into an SDS Max chuck, and an SDS Max accessory does not fit directly into SDS Plus. Their shank sizes and fastening geometry differ. A HEX accessory also cannot be installed in an SDS chuck without a suitable, manufacturer-approved conversion solution. An adapter does not increase the permitted impact energy or duty class of the tool.A heavy accessory on a smaller tool can overload the chuck, gearbox, and impact mechanism.An adapter may increase overall length, play, and vibration.Some adapters are intended only for rotation and not for hammer operation.Use only combinations approved by the tool and adapter manufacturers. ImportantNever force an accessory into place or use homemade sleeves or an unsuitable chuck. Incorrect retention can damage the tool and allow the accessory to be ejected. 5 Practical Steps for Choosing a Fastening System 1Define the main taskDecide whether you will mainly drill small holes, work with large diameters, or perform intensive demolition. 2Select the tool classConsider SDS Plus for light and medium tasks, SDS Max for heavy drilling, and the appropriate HEX system for specialised demolition. 3Check the accessory shankConfirm the system and exact size. With HEX, also inspect the locking groove, collar, and complete retention geometry. 4Compare technical specificationsConsider impact energy, maximum drilling diameter, permitted core bits, tool weight, and duration of work. 5Check future accessory availabilityMake sure the drill bits, chisels, and core bits you need are available in the selected system and suitable sizes. Common Mistakes When Choosing SDS and HEX Treating HEX as one standard size. Hex shanks differ in size and locking geometry.Choosing SDS Plus or SDS Max only by impact energy. The task, diameter, weight, and accessories also matter.Choosing SDS Max for small holes. A heavy tool can be inconvenient and inefficient for precise work.Continuously using SDS Plus for heavy demolition. This can accelerate chuck and mechanism wear.Treating an adapter as full compatibility. It may limit the operating mode and permitted load.Ignoring the maximum permitted accessory size. Not every size in the same system is suitable for a specific tool.Failing to clean and lubricate an SDS shank as instructed. Dust and dry friction accelerate chuck wear. Frequently Asked Questions Are SDS Plus and SDS Max accessories interchangeable?Not directly. Their shanks have different sizes and geometry. Use only a manufacturer-approved adapter suitable for the required operating mode. Which is better: SDS Plus or SDS Max?Neither is universally better. SDS Plus is convenient for light and medium work; SDS Max is designed for large holes and heavy demolition. What is the SDS Plus shank diameter?The nominal SDS Plus shank diameter is generally 10 mm. The working diameter of the drill bit can be smaller or considerably larger. What is the SDS Max shank diameter?The nominal SDS Max shank diameter is generally 18 mm. It is designed for higher impact and rotational loads. Are all HEX chisels interchangeable?No. The exact hex size, shank length, and locking groove or collar design must match. Can a HEX tool be used for drilling?It depends on the tool and the specific system. Many HEX demolition hammers are impact-only, although specialised drilling HEX systems also exist. Can an SDS Plus bit be used with an SDS Max tool?Only with a suitable manufacturer-approved adapter. Observe the limits on operating mode, accessory size, and load. Why is an SDS Max tool heavier?It has a larger chuck, impact mechanism, and powertrain components designed for larger accessories and demanding loads. Should an SDS shank be lubricated?If required by the tool instructions, apply a small amount of suitable grease to a clean shank. Excess grease may collect dust and contaminate the chuck. How can accessory compatibility be checked quickly?Compare the chuck marking, shank system, and size, then check the permitted accessory types and limits in the tool manual. Read AlsoHow to choose handheld power tools.What is impact energy (J)?What is rotational speed (RPM)?What is torque (N·m)?How to choose tool power (W).Related CategoriesRotary hammers.Electric demolition hammers.Pneumatic demolition hammers.SDS Plus drill bits and chisels.SDS Max drill bits and chisels.HEX chisels and demolition accessories. Next article: Types of chucks and their applications.
Typical accessoriesSDS Plus drill bits, small and medium core bits, pointed and flat chisels, and other compatible accessories.
AdvantagesLow tool weight, quick accessory changes, wide availability, and good control in everyday installation work.
LimitationsNot intended for very large drill bits, heavy core bits, or prolonged intensive demolition.
Typical accessoriesSDS Max drill bits, large core bits, breakthrough bits, points, flat chisels, and spade chisels.
LimitationsTools and accessories are heavier and more expensive and can be inconvenient for small, precise holes.
Typical accessoriesBull points, flat chisels, wide spades, asphalt cutters, and specialised demolition accessories.
LimitationsMultiple sizes and locking designs, limited interchangeability, and often an impact-only operating mode.
