SDS-plus vs SDS-max: which rotary hammer bits fit which tool

01What is an SDS shank?

An SDS shank is a slotted bit shank for rotary hammers: grooves in the shank carry the turning force and lock the bit in the tool, while letting the bit slide back and forth so the hammer's blow reaches the tip. A jaw chuck clamps a round shank tight; an SDS holder deliberately leaves the bit free to move along its axis.

The bit itself is usually a masonry bit: a steel body with a brazed tungsten carbide tip, run with hammer action. Starrett's SDS-plus masonry bits, for example, use a 130 degrees carbide tip. The shank system, plus or max, only decides which hammer the bit fits.

02How do SDS-plus and SDS-max shanks differ?

SDS-plus has a 10 mm shank with 2 open + 2 closed grooves; SDS-max has an 18 mm shank with 3 open grooves and a locking feature. Tanner Bolt, BAER and GTSE agree on both diameters.

The sources disagree on how SDS-max locks. Tanner Bolt describes extra closed grooves alongside the open ones; GTSE describes a locking segment instead. Either way, the open-groove layout and the larger diameter mean an SDS-max shank cannot enter an SDS-plus holder, and an SDS-plus shank is far too thin for an SDS-max holder to grip.

Brand naming adds one more label. Hilti calls its SDS-plus connection TE-C on its UK bit sets, so a Hilti bit marked that way fits SDS-plus hammers from other makers. A matching Hilti label for SDS-max was not confirmed on a Hilti page, so it is not given here.

03Which rotary hammers take SDS-plus and which take SDS-max?

Light and mid-size rotary hammers, corded and cordless, take SDS-plus; heavy rotary and demolition hammers of roughly the 5 kg class and up take SDS-max. BAER and GTSE both place SDS-max at that weight class, and Bosch's GBH 5-40 D SDS-max hammer is an example from it.

Every rotary hammer in the AccessoryFit tool database is an SDS-plus tool, from corded models by Bosch and Makita to cordless models on DeWalt's 20V MAX, Makita's 18V LXT and Milwaukee's M18 batteries. That reflects the tools in the database rather than the whole market, but it shows how widely one bit system spans brands and batteries. Batteries do not cross brands, but SDS-plus bits do, as the guide to which cordless batteries fit which tools explains from the battery side.

04How long can you drill with a rotary hammer, and does pushing harder help?

Not long at a stretch, and no. UK HSE's 2019 hand-arm vibration guidance (L140) gives a good-quality modern rotary hammer about 15 minutes to reach the daily exposure action value, counting trigger time only, and about one hour to reach the exposure limit value. That applies to SDS-plus and SDS-max tools alike, so the choice of system does not buy extra trigger time; the bit and the technique are where you have control.

Leaning on the hammer works against you. A 2020 International Journal of Industrial Ergonomics test-bench study of one 10 kg rotary hammer drilling 19 mm holes in concrete found that 17% more concrete could be drilled per day within ISO 5349 vibration limits when the operator pushed with about 90 N rather than 160 N, because handle vibration fell and the time before the action limit grew. The authors advise a push force of about 90 to 100 N: enough to keep the bit seated, and no more. A sharp bit inside the hammer's rated range matters for the same reason.

Dust is the other cost of SDS drilling in concrete. A 2019 University of California, Berkeley test-bench study drilled concrete with a rotary hammer and found respirable quartz many times the ACGIH limit with no extraction; fitting either a drilling shroud or a hollow vacuum bit brought it below the detection level, a reduction of 98.7% or more. Both SDS-plus and SDS-max hollow bits and shrouds are sold, so either shank system can be paired with a vacuum.

05What size holes does each system drill?

SDS-plus covers small and medium holes and SDS-max covers large ones, with an overlap in the middle. Bosch gives its SDS-plus GBH 2-28 F a concrete range of 4 to 28 mm with hammer bits, and its SDS-max GBH 5-40 D a range of 12 to 40 mm, with core cutters taking that hammer to larger holes still. Bosch rates the SDS-max example at 8.5 J of impact energy.

Sources do not agree on the upper limit of SDS-plus bits in general. BAER, GTSE and Tanner Bolt each give a slightly different top size, and Bosch's own figure for one hammer sits among them. The useful reading is that the hammer's own specification sets the limit, not the shank system: a light SDS-plus hammer may be rated for less than the largest SDS-plus bits on sale. Bosch's spec sheet also gives the GBH 2-28 F an optimum range well inside its maximum, which is worth checking on any hammer before buying large bits.

For general masonry, carbide-tipped bits are the norm, and common masonry bit sizes run across both systems. The shortlist of carbide masonry bits for concrete applies these shank rules to specific products.

06Can SDS-max bits fit an SDS-plus hammer?

No. The shanks are 18 mm and 10 mm, and the two systems are not interchangeable in either direction without an adapter. A common belief is that the two are close enough to swap; GTSE and Tanner Bolt both say otherwise.

Adapters only work one way. GTSE notes that adapters let an SDS-max hammer take SDS-plus bits for lighter work, while the reverse is not practical. That suits a crew that owns one heavy hammer and wants to use its stock of smaller bits in it; it does not turn a light hammer into a heavy one.

07Can a rotary hammer take ordinary drill bits or hex bits?

Yes, through an adapter, but only in rotation-only mode with the hammer action switched off. Bosch's HA3JAWC gives an SDS-plus hammer a 1/2 in keyless chuck for round-shank bits, and Makita's B-59259 lets an SDS-plus hammer drive 1/4 in hex bits. Makita, McMaster-Carr and Starrett all describe these adapters as rotation-only.

One source differs. Bosch's HA3JAWC page says the adapter can be used in hammer mode, which conflicts with Makita, McMaster-Carr and Starrett and may be a page error. The safer reading, and the one used on this page, is rotation only. A common belief is that a chuck adapter turns a rotary hammer into a hammer drill for round-shank masonry bits; the adapter makers describe it for rotation-only drilling with standard bits. Makita adds that its hex adapter has a short shank to help prevent damage if hammer mode is selected by mistake.

What modes does a rotary hammer have, and which one suits an adapter?

Milwaukee's manual for its SDS-plus rotary hammers lists 3 modes: rotation only, rotary hammer, and hammer only, and says to stop the motor before changing mode. Rotation only is the setting for adapters and for drilling steel or wood; rotary hammer is the setting for carbide masonry bits, which are normally run with hammer action. The same manual says Milwaukee's 2715-20 SDS-plus hammer needs its chuck adapter kit (48-66-1370) for drill-only work in steel and wood, which is the maker confirming the adapter route for round-shank bits rather than a bare SDS holder.

The opposite move, an SDS bit in a drill's jaw chuck, is not covered by any source used here. An SDS shank is designed to slide in an SDS holder rather than be clamped, so the bit belongs in an SDS tool. Chuck capacity and what a jaw chuck is made to hold are covered in the guide to bit shanks a drill chuck can hold.

08Should you use an SDS hammer on tile?

Not with hammer action on glazed or porcelain tile. Bosch says to drill tile on the rotary setting only, Milwaukee rates its tile and glass bits for drill drivers only, and Makita says its tile bits are for a driver-drill. Diamond tile drills and diamond hole saws for porcelain, glass and stone must always be cooled with water, and glass bits run at low speed; neither is a job for hammer action.

The bits suited to that first step are compared in the guide to diamond and carbide bits for tile. A rotary hammer in rotation-only mode with a chuck adapter can drive such a bit, provided the bit maker's speed and cooling guidance is followed.

09When does an SDS bit not fit or not work?

An SDS bit fails whenever the shank system, the hammer's rating or the mode is wrong for it. These are the cases in the sources on this page:

• SDS-max bit in an SDS-plus hammer. The shank is too large, and no practical adapter exists.
• SDS-plus bit in an SDS-max hammer without an adapter. The thinner shank cannot be held.
• Bit beyond the hammer's rated range. The hammer's spec, such as Bosch's for the GBH 2-28 F, sets the limit.
• Chuck or hex adapter used with hammer action on. The adapter can be damaged.
• Hammer action on tile or glass. These need diamond or glass bits at low speed, with water for diamond.
• Older or uncommon shank systems. Other shank systems, such as spline, exist on some heavy hammers, but their dimensions were confirmed by only one source and are not covered here.

10How do you check which bits a rotary hammer takes?

Four checks against the hammer and its manual confirm which bits it takes before buying a set.

1. Read the tool holder on the hammer. The nameplate, manual or product page names the system, SDS-plus or SDS-max; Hilti uses its own label for SDS-plus.
2. Check the rated drilling range. The manual or spec sheet gives the concrete range with hammer bits, and sometimes an optimum range inside it.
3. Measure an old bit's shank if unsure. A shank near 10 mm is SDS-plus; one near 18 mm is SDS-max.
4. Set the mode for adapters. When fitting a chuck or hex adapter, stop the motor and switch the hammer to rotation-only before drilling, as Milwaukee's manual describes for its mode selector.

11Where do you go next for masonry bits?

With the shank system settled, the bit choice comes down to material and size. All drill bit guides are collected under drill bit fit and buying guides, and the guide to twist, masonry and specialty bits explains where SDS bits sit among the rest. For any specific hammer model, the model-by-model accessory lookup lists the bits that fit, and every other fit question is in the fit guides by tool.

12Questions readers ask