Rotary hammer buyers argue brands; the machine's real identity is its shank standard. SDS-Plus and SDS-Max are not quality tiers, they are two different tool classes built around a 10 mm and an 18 mm shank respectively, and every downstream decision, hole capacity, chisel duty, weight and consumable inventory, follows from that split [S1]. Select the standard by the anchor schedule and the demolition scope, then choose the machine inside it.
Two Shanks, Two Machines
SDS-Plus tooling locks into a 10 mm shank with closed slots; the interface is light, precise and fast to change, and it carries the bulk of anchor drilling in concrete, brick and block [S1]. SDS-Max takes an 18 mm open-slotted shank that transfers substantially more impact energy and torque into the bit. The physical gap between the interfaces is the selection boundary: machines are built around their shank's energy class, so stepping up hole size means stepping up machines [S1][S2].
Hole Diameter Sets the Standard
The working rule is straightforward: anchor and fixing holes to roughly 30 mm in concrete belong to SDS-Plus; larger holes, and anything drilled with large core or through-hole bits, move to SDS-Max [S1]. Below the boundary, SDS-Plus machines are faster per hole, lighter on the arm and cheaper to feed with bits. Above it, an SDS-Plus machine asked to drive oversized bits delivers slow progress, seized shanks and shortened tool life, while an SDS-Max machine at its designed hole range keeps production rates and operator exposure sane [S2][S3].
| Selection factor | SDS-Plus | SDS-Max |
|---|---|---|
| Shank interface | 10 mm, closed slots | 18 mm, open slots |
| Practical hole band | Up to about 30 mm in concrete | Roughly 30 mm upward through large diameters |
| Chisel and demolition duty | Light, intermittent chipping | Sustained breaking, bushing and demolition |
| Tool weight class | Lighter, overhead-capable | Heavier, two-hand floor work |
| Bit inventory cost | Lower per bit | Higher per bit, heavier consumable line |
| Typical job mix | Anchor drilling, fixings, mechanical installs | Structural openings, slab work, heavy demolition |
Chisel Duty Is the Second Question
Drilling capacity is only half the purchase. Demolition chisels, pointed breakers, flat spades and bushing tools load the shank in impact and torsion continuously rather than intermittently, and the 18 mm SDS-Max interface is dimensioned for exactly that sustained beating [S1][S2]. Crews whose schedule is heavy on tile screed removal, slab breaking, chipping out concrete or cutting channels should buy SDS-Max first and keep an SDS-Plus machine for the anchor work, not the reverse. The trade is weight and fatigue: the heavier class belongs on the floor and at waist height, while overhead fixing work stays in the lighter machine's territory [S3].
Impact Energy and Application Match
Within each shank class, impact energy separates the light and heavy machines. SDS-Plus machines span from compact low-energy units suited to small anchors and masonry through heavier high-energy models that accelerate drilling in hard concrete; SDS-Max machines start where that top band ends and run to multi-joule demolition performers [S2][S4]. The disciplined way to buy is from the application: list the anchor diameters and embedment depths on the drawings, list the demolition scope, then size impact energy to the hardest 20 percent of the work rather than the average hole. Manufacturer class tables map hole diameter to machine class directly [S4].
Duty Cycle, Wear and Running Cost
Continuous heavy work is where the classes separate economically. SDS-Plus mechanisms pushed into sustained chisel duty run hot, consume bits faster and land in service more often; field comparisons of professional-grade machines consistently show the heavier SDS-Max platform holding up under demolition schedules that would consume a lighter tool [S2][S3]. Conversely, a fleet of SDS-Max machines doing anchor-only work pays for capability it never uses, in tool price, in weight carried up ladders and in slower small-hole cycle times.
Practical Selection Sequence
Run the decision in order. First, the anchor schedule: hole diameters and depths, and the share of work above roughly 30 mm. Second, the demolition scope: hours of chisel work per week and the materials to be broken. Third, ergonomics: overhead versus floor work, operator exposure and vibration budgets. Fourth, consumables and service: bit inventory across both standards and local service support for the chosen platform [S1][S4]. Most professional fleets land on one machine of each class, and the procurement error to avoid is asking either one to live in the other's territory.
Cordless Platforms and Fleet Logic
The SDS-Plus class is now dominated by cordless platforms, and battery-system logic belongs in the purchase decision: crews standardized on one battery family gain charging simplicity and cross-compatibility with grinders and drills, at the cost of locking the anchor-drilling fleet to that ecosystem. Cordless SDS-Max machines exist but the energy demand of heavy demolition favors corded power where the work is stationary, floor-level slab and wall breaking, which is exactly where a cord is trivial to manage. The rational fleet split for a general contractor is cordless SDS-Plus for mobility and overhead work, corded SDS-Max for demolition throughput [S2][S3].
Vibration, Dust and Operator Exposure
Both shank classes transmit hand-arm vibration, and exposure limits are written into occupational health rules in most markets. Heavier SDS-Max work demands attention to vibration-reducing handles, anti-vibration gloves as a supplement rather than a fix, and rotation of operators on sustained chisel shifts. Silica dust control is now part of the drilling specification, not an option: extraction shrouds, dust-collection bits and wet systems for hole drilling are consumable lines the RFQ should price alongside the machine. A tool purchased without its dust and vibration accessories is not yet compliant for the work it was bought to do [S1][S3].
Anchor Schedule First, Then the Machine
The most underused selection tool is the project's own anchor schedule. List every fixing on the drawings by diameter and embedment depth, count the holes per diameter, and read the totals against each shank class's practical band. A schedule dominated by 8 to 16 mm anchors with a handful of 24 mm sleeves argues for one high-energy SDS-Plus machine and a proper bit set, not an SDS-Max platform idling through small work. A schedule with through-holes at 40 mm and up, or a demolition scope in the same contract, argues the other way. Buy bits for the scheduled diameters at the same time as the machine, because the bit cabinet, not the shank choice, is what stops a crew mid-morning [S1][S4].
Service and Fleet Standardization
Fleet logic compounds the shank decision. Standardizing one brand platform per class consolidates batteries, chargers, service parts and the wear items that fail fastest: chucks, seals and brushes on corded units. When a mixed fleet is unavoidable, at minimum standardize the SDS-Max demolition line so breaker points, spades and bushing tools interchange across machines. Serviceability should be checked at purchase, published parts availability and local turnaround, because a down rotary hammer in a fixing crew stops the whole line behind it [S2][S3].