SDS-Max Carbide Head Geometry Explained: ZHMAX-5X, ZHMAX-7, and ZHMAX-8

Why Head Geometry Determines SDS-Max Performance

In a rotary hammer drill bit, the carbide insert at the tip does two things simultaneously: it cuts material under heavy impact energy, and it clears the resulting debris out of the hole so the next impact stroke lands on fresh material.

A standard SDS-Max shank delivers 8–20 joules of impact energy per stroke. At that energy level, the geometry of the carbide head — how many cutting edges it has, how they are oriented, and how the side faces are shaped — determines whether the bit converts most of that energy into forward progress, or wastes it on friction, deflection, and debris compaction.

This is why two SDS-Max bits with identical diameter, identical steel grade, and nominally identical carbide quality can produce dramatically different drilling speeds in reinforced concrete. The variable is not what the bit is made of. It is how the cutting geometry is arranged.

The ZHMAX series is built around three distinct carbide head architectures — each a different engineering answer to this problem.

The Three ZHMAX Tiers at a Glance

ZHMAX-5X: Standard 4-Cutter Brazed Geometry

ZHMAX-5X uses the conventional four-cutter brazed carbide geometry that has been the SDS-Max standard for two decades. A single carbide insert is controlled-atmosphere brazed into a four-slot head machined into the steel body.

What it does well. Reliable, predictable performance in general concrete, masonry, and stone. Ø12–25mm range, lengths 200–600mm. YG8C virgin carbide and controlled-atmosphere brazing give ZHMAX-5X a meaningful life advantage over mass-market bits that use recycled carbide and conventional furnace brazing — even though the geometry looks similar from the outside.

Where it reaches its limit. In heavily reinforced concrete, the flat four-cutter geometry produces increasing deflection when the cutting edges contact rebar, and debris evacuation slows at larger diameters. Drilling speed drops, bit temperature rises, and carbide tip wear accelerates. These are not quality defects — they are the physical limits of the geometry itself.

Best for: General construction, masonry anchoring, foundation drilling, applications where the concrete is not continuously reinforced and maximum speed is not the primary requirement.

ZHMAX-7: Staged Multi-Insert 4-Cutter Geometry

ZHMAX-7 is not a conventional symmetric cross head. It is a staged three-insert, four-effective-edge architecture: one full-width primary carbide blade sits forward and carries the leading impact, while two inclined side inserts are set back axially and follow around the gauge circle.

Primary blade first. The full-width blade creates two leading diametrical edges and preserves the direct penetration character associated with a two-cutter. It fractures the concrete before the side inserts reach full engagement.

Side inserts second. The two following YG11C inserts support peripheral cutting, stabilize the head, and maintain finished hole diameter. Their inclined placement creates progressive contact rather than forcing four equivalent wings to strike at the same axial level, reducing the tendency to snag when contact is uneven around rebar or hard aggregate.

Controlled flute volume. Open head pockets give crushed material a direct route into the helix. The flute remains large enough for deep-hole dust transport, but the 42CrMo body retains a substantial core and lands for impact transfer, torsional reserve, tracking, and fatigue resistance. Maximum-looking flute depth is not the goal; the complete load path is.

Controlled-atmosphere brazed multi-insert construction. The three separate YG11C carbide components are seated in dedicated body pockets and controlled-atmosphere brazed for repeated heavy-impact service. The design combines direct leading-edge penetration with four-edge gauge support and an open debris path.

Diameter range: Ø16–45mm, lengths 320–920mm; confirm the exact diameter-length combination by RFQ.

Best for: Reinforced-concrete service penetrations, large heavy-anchor holes, bridge and tunnel work, deep drilling in dense concrete, and hard natural stone where penetration, gauge retention, and torsional reserve matter together.

ZHMAX-8: Full-Head Solid Carbide

ZHMAX-8 represents the most engineered approach to SDS-Max geometry currently available anywhere in the market. Instead of brazing carbide segments into a steel body, the entire cutting tip is a monolithic solid carbide component, joined to the steel shank by resistance friction welding.

Four symmetrical 90° cutting edges are precision-ground into the solid carbide head. The bond interface is engineered to survive the repeated high-energy shock loads of SDS-Max drilling — eliminating the progressive fatigue failure mode that limits large brazed joints in extreme applications.

Why this geometry exists. At extreme impact energies and in continuously reinforced high-strength concrete, brazed joints can micro-fatigue over thousands of cycles. A resistance-friction-welded solid carbide head removes the brazed-joint failure mode entirely. Bosch documents 5× service life for its SpeedXtreme class versus conventional brazed bits in controlled test conditions at equivalent diameters.

The diameter constraint. The diffusion-bonding process is the binding technical constraint across the entire industry. As the tip diameter increases, the bonding interface area grows, thermal stress during the diffusion process becomes harder to control, and achieving consistent bond strength without micro-fracture is an unsolved mass-production problem. Bosch's own SpeedXtreme line — built on proprietary diffusion-bonding technology and decades of carbide manufacturing experience — extends to 25mm (1 inch) maximum. No manufacturer currently offers full-head diffusion-bonded SDS-Max bits above 25mm in volume production. This is not a Chinese supply limitation. It is an industry-wide ceiling.

Best for: The highest-intensity SDS-Max applications: continuous heavy-duty drilling exceeding 4 hours per day, work in extremely dense concrete above 50 MPa compressive strength, demolition-interface work where bit longevity is the dominant cost driver.

Diameter range: Ø16–25mm, lengths 340–920mm.

Application Selection Matrix

OEM Sourcing Note

For distributors and tool brands evaluating Chinese SDS-Max supply across these geometry tiers:

ZHMAX-5X is available from multiple Chinese manufacturers. The differentiating factors — carbide grade verification, brazing method, concentricity tolerance — are worth checking, but the supply base is broad.

ZHMAX-7 in a true multi-segmented cutter format — not a cosmetically differentiated standard four-cutter — is available from very few Chinese manufacturers. The geometry requires custom carbide segment tooling and higher CNC precision in the steel body. Zhonghuan is one of the first to bring this class to OEM volumes in the Chinese market.

ZHMAX-8 is in production at small diameters — Ø3–25 (for SDS-Max, the Ø16–25 slice), one-piece tungsten carbide, the same construction as Bosch Speed Xtreme. Full-head solid carbide is inherently a small-diameter category: it caps near Ø25 even at Bosch, so above that the segmented ZHMAX-7 and 3-plate / 6-edge heads carry the load. Tell us your diameter and material and we'll confirm the right head.

Related Procurement Programs

If you are sourcing SDS-Max drill bits at distribution volumes, these programs cover the procurement questions buyers typically ask next.

• SDS Drill Bits Manufacturer & Wholesale Supply for Distributors — OEM and wholesale SDS drill bit supply for importers, distributors, and tool brands: SDS-Plus, SDS-Max, carbide tips, 2-cutter and 4-cutter heads, packaging options.
• Zhonghuan SDS-Max Product Range — Full ZHMAX-5X, ZHMAX-7, and ZHMAX-8 specifications, diameter and length tables, and OEM inquiry.