Bosch SDS max-7, Speed-X and 'QX minera' — and Zhonghuan's own ZHMAX-7
What ZHMAX-7 is
ZHMAX-7 is Zhonghuan's multi-insert 4-cutter: one full-width primary carbide blade and two inclined, axially set-back side inserts, 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 sells hard-rock bits under the names SDS max-7 (Europe, Latin America), Speed-X (North America) and, in the Peruvian mining channel, 'QX' (broca minera QX). Those are Bosch products with Bosch's own descriptions; ZHMAX-7 is built and specified from Zhonghuan's drawing. If you run a max-7-class bit today, send its reference and we quote ZHMAX-7 for the same application — diameter, length and rock — under your own brand.
Construction, Decoded
ZHMAX-7 RFQ name: multi-insert 4-cutter. Count the three physical carbide components separately from the four active cutting edges. The full-width primary blade leads; two inclined side inserts sit axially behind it and support the outer gauge. The approved drawing fixes the insert profile, joining method and finished bore diameter.
ZHMAX-7 has three brazed carbide components:
- One full-width primary blade. A single piece of carbide spanning the full drilling diameter. It takes first contact with the rock face, so the impact energy goes into breaking rock instead of loading the outer corners of the head.
- Two inclined side inserts. Small carbide inserts brazed at the periphery and set back axially behind the primary blade. They add peripheral engagement, 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.
- Brazed multi-insert head, distinct from a one-piece full-carbide head. ZHMAX-7 uses three separately brazed carbide components. ZHMAX-8 is a separate one-piece carbide-head program joined to its steel body by Resistance Friction Welding (RFW). Bosch max-8X is a full-carbide-head reference with Bosch’s welded connection. Specify the construction and joint for the actual SKU rather than inferring them from cutter count.
| 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 | Zhonghuan's own drawing: full-width primary blade + 2 inclined, axially set-back side inserts, controlled-atmosphere brazed virgin carbide, 42CrMo body |
Different names, different drawings. Procurement teams comparing quotes should compare construction — primary-blade width, side-insert position and angle, 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 multi-insert-versus-Y-cutter question in Y-cutter vs multi-segmented carbide.
Why the Multi-Insert Layout Suits 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. With the side inserts set back behind the primary blade, the primary blade takes first contact and the periphery engages after it.
- Supported cutting edges. Each brazed insert sits in its own seat in the forged head, so seat geometry and braze quality — not one thin edge — carry the load. Seat support, insert positioning and braze quality decide whether the head survives hard, abrasive rock.
- Debris path. Open head-to-flute space carries cuttings 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 | Carbide grade specified by approved drawing, with batch material documentation |
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 full-width primary blade 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) | Full-width primary blade + 2 inclined, axially set-back side inserts | 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.