In brief, the rotary hammer is meant for jobs that require a more powerful impact. Often times rotary hammers and hammer drills are grouped into a category referred to as “hammer drills,” but that is somewhat of a misnomer when applied to rotary hammers. As an analogy, the hammer drill is akin to drumming your fingertips on a table, while the rotary hammer is like a metered pounding of your fist on the table. This guide will help to further clarify the difference.
Defining Hammer Drills and Rotary Hammers
Both the rotary hammer and the hammer drill turn a drill bit and provide a hammering action. Both tools are made by brand name manufacturers such as Bosch, DeWalt, Makita and Milwaukee, as are their respective bits and attachments. But their differences begin with how they are designed and what they can do, as well as the features and accessories that expand their capacities.
- Uses a rapid clutching action to produce a hammering effect on the turn of the hammer drill bit
- Sufficient for drilling holes up to about 1 inch in diameter
- Uses either a keyed or a keyless three-jaw chuck, similar to any standard drill
- Uses an actual hammering action within the drill to deliver a more powerful blow
- Sufficient for consistent use in drilling larger holes, up to a 2-inch diameter
- Rather than a chuck, rotary hammers use specific slotted drives
- Some include a “stop rotation” feature which allows for the tool to be used like a jackhammer, making it a popular tool for demolition projects
Due to the greater force of the rotary hammer, the differences extend to onboard components as well as the bits they use.
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Rotary Hammer Drive Types
The three most common rotary hammer drives are:
- SDS/SDS+: also referred to as “SDS plus,” the meaning of the letters is often disputed in the trades but it is generally accepted that SDS stands for “slotted drive system.” SDS and SDS+ are the smallest of the rotary hammers and are limited to about a 1⅛-inch solid bit diameter capacity. The shanks of these bits and accessories have single drive slots on opposing sides.
- SDS-Max: the bigger sibling of the SDS+, SDS-Max can have a solid bit capacity of up to 2 inches on some rotary hammers. Shanks for SDS-Max bits and accessories are characterized by two drive slots on one side, and a single slot on the opposite side. Some of these include a stop-rotation feature.
- Spline: like the SDS-Max, this drive style can accommodate a bit capacity of up to 2 inches. Spline shanks on bits and accessories are characterized by evenly spaced teeth around their entire circumference, similar in look to a gear. Some of these include a stop-rotation feature.
All three drive types are industry standards, so they are interchangeable among brands and within the same drive.
More on Rotary Hammer Features, Capabilities, and Accessories
All rotary hammer drives have core bits available for drilling holes larger than the solid bit capacity. Also available are SDS bits for cutting rebar (AKA “rebar cutters”), and stop bits, which are used for drilling holes to a specific depth for anchors.
The stop-rotation feature, available on some rotary hammers, enables chiseling, scraping, digging and other functions achievable through the use of use specialized rotary hammer bits and rotary hammer accessories such as coring bits, ground rod drivers, chisels, floor scrapers, clay spades, and others.
Adapters will allow SDS+ bits to be used in SDS-Max and spline drive tools; however, SDS-Max and spline drive hammers cannot be used with SDS+ rotary hammers.
Product Compliance and Suitability
The product statements contained in this guide are intended for general informational purposes only. Such product statements do not constitute a product recommendation or representation as to the appropriateness, accuracy, completeness, correctness or currentness of the information provided. Information provided in this guide does not replace the use by you of any manufacturer instructions, technical product manual, or other professional resource or adviser available to you. Always read, understand and follow all manufacturer instructions.