One Head, Three Market Names: SDS max-7, Speed-X, 'QX minera'
What this head actually is
The multi-segmented cutter SDS-Max head is built from one full-width carbide plate ground to a multi-segmented profile, plus two small inclined side cutters, all brazed into a forged steel head. It is not a full solid-carbide head, and it is not a symmetric 4-cutter cross. Bosch catalogs this architecture as SDS max-7 in Europe and Latin America and markets the same construction as Speed-X in North America; in the Peruvian mining channel the same head is sold under the 'QX' (broca minera QX) name. Zhonghuan manufactures the same architecture class factory-direct as the ZHMAX-7 — for OEM buyers who want max-7-class hard-rock performance under their own brand.
Construction, Decoded
Strip away the marketing names and the head is three brazed carbide elements:
- One multi-segmented cutter plate. A single piece of carbide spanning the full diameter. The crown is ground into stepped segments rising toward the centring point, so each segment engages the rock in sequence instead of the whole edge landing at once. That staging is what "progressive" means in practice: on an uneven mine face, first contact happens on one small segment, and the impact energy goes into breaking rock instead of chipping carbide.
- Two inclined secondary cutters. Small carbide inserts brazed at the periphery, perpendicular to the main plate, completing the 4-cutter layout. They round out the hole and carry the gauge diameter as the bit wears — the difference between a hole that keeps accepting a ø25 mm cartridge at depth and one that pinches shut.
- A brazed joint, not a monoblock full-carbide head. Full solid-carbide heads are a different tier: the Bosch SpeedXtreme / max-8X class bonds the entire carbide head to the body by diffusion welding, and our own ZHMAX-8 class uses Resistance Friction Welding (RFW) instead — both routes keep this tier in premium construction diameters on cost and size grounds. The max-7 class stays with a brazed plate: at Ø28–38 mm mining sizes it delivers the multi-segmented cutter geometry with a toughness reserve, at the economics that high-consumption blast-hole work demands.
| Name | Market | Notes |
|---|---|---|
| Bosch SDS max-7 | Europe, Latin America (catalog name) | Bosch's hard-rock / reinforced-concrete multi-cutter line, PGM certified |
| Bosch Speed-X | North America | Same construction under the North American line name |
| 'QX' / broca minera QX | Peruvian mining channel | Same head architecture sold as the Bosch mining bit — retail refs 1618596443/444, lengths 450 / 570 / 920 mm |
| Zhonghuan ZHMAX-7 | Factory-direct OEM — your brand | Same architecture class: brazed multi-segmented cutter plate + 2 inclined side cutters, controlled-atmosphere brazed virgin carbide, 42CrMo body |
One geometry, four names. Procurement teams comparing quotes should compare construction — plate profile, side cutters, braze process, body steel — not the label on the flute. How this head family relates to flat-cross and full-carbide tiers is covered in SDS-Max carbide head geometry (ZHMAX-5X / 7 / 8), and the segmented-vs-Y-cutter question in Y-cutter vs multi-segmented carbide.
Why Progressive Segments Win in Hard Abrasive Rock
- Staged engagement on uneven faces. A mine face is never flat. A flat-ground head landing on a high spot concentrates the full impact on one corner — the classic chipping failure. The progressive crown meets the rock one segment at a time.
- Shearing action. The curved segment profile attacks rock at an angle, shearing rather than purely crushing — more advance per joule in quartzite-class abrasive rock.
- Debris path. The segment steps break cuttings smaller and feed them into the flutes. In 450–920 mm blast holes, dust evacuation — not carbide sharpness — is usually the speed limit.
- Gauge retention. The two side cutters carry the diameter, keeping the hole round and full-size deep into the bit's life, so cartridges seat and bits don't jam.
When the rock is medium-hardness and the priority is the roundest possible hole, the 3-cutter / 6-edge head (Ultimax-168 class) is the better pick. The full head-selection trade-off for mining duty is on the SDS-Max mining drill bits program page.
ZHMAX-7 Size Program
| Spec | Range | Notes |
|---|---|---|
| Diameter | Ø16–45 mm | Ø32 mm is the mining volume size — a 32 mm hole fits ø25 mm (1") cartridges with working clearance |
| Total length | 320–920 mm | Mining lengths 450 / 570 / 620 / 920 mm — the market-standard blast-hole lengths; other lengths by drawing |
| Shank | SDS-Max | Universal — fits all SDS-Max rotary hammers |
| Body | 42CrMo alloy steel, heat-treated | Fatigue resistance for repeated 12–20 J impact and off-axis hand drilling |
| Carbide | Controlled-atmosphere brazed virgin carbide; YG11C class on mining sizes | Ceratizit tips available on request, with supplier mill certificate |
Trade note: Latin American buyers quote mining bits by working length in centimetres — “(40)”, “(60)”, “(80)” ≈ 400 / 580–600 / 800 mm usable. Quotations state both lengths per SKU.
Materials, Process & QC
- One-piece multi-segmented cutter plate in virgin carbide — never recycled material; why that matters for gauge life is covered in virgin vs recycled tungsten carbide.
- Controlled-atmosphere brazing. Whole-joint wetting in a controlled-atmosphere furnace — the braze survives the heat cycling of deep blast holes that defeats spot induction joints.
- 42CrMo body with full heat treatment — the steel-grade decision is broken down in 40Cr vs 42CrMo for SDS drill bit bodies.
- QC per production lot: hardness (HRA on carbide, HRC on body), dimensional and runout checks, metallographic cross-section of the braze joint, and a witness drilling test. Carbide grade is documented by the supplier mill certificate.
Where ZHMAX-7 Sits in the Zhonghuan SDS-Max Line
| Head | Geometry | Duty |
|---|---|---|
| ZHMAX-5X | Standard 4-cutter brazed cross | General construction concrete |
| 6-edge (Ultimax-168 class) | 3 carbide plates forming 6 edges, self-centring | Medium rock, roundest holes — program page |
| ZHMAX-7 (this page) | Multi-segmented cutter plate + 2 inclined side cutters | Hard abrasive rock, deep blast holes, rebar-tolerant heavy drilling |
| ZHMAX-8 class | Full solid-carbide head, Resistance Friction Welded (RFW) | Rebar-rich reinforced concrete — full carbide head SDS-Max program |
OEM & Private Label
ZHMAX-7 runs as a standard OEM program: laser-etched branding on the body, custom packaging, MOQ 200 pcs per size on the mining program, samples shipped freight-paid for witness testing, ISO 9001 manufacturing with material certificates per lot. Spanish-speaking buyers can quote against catalog names — send "broca Bosch para minería", "broca QX" or a DeWalt / Makita SKU and we map it to the geometry and quote the ZHMAX equivalent. The full blast-hole program (6-edge + ZHMAX-7, machine pairing, RFQ guidance) is on the SDS-Max mining drill bits manufacturer page.