Why Reinforced Concrete Is Different
Plain concrete is cement, sand and aggregate: a rotary hammer bit breaks it by impact and the flutes carry the dust out. Reinforced concrete adds steel bars, typically 8–32 mm, in a grid through the section. Steel does not fracture under impact; it has to be cut.
That is where an ordinary bit runs out of road. Bosch states it plainly for its own range: regular two-cutter bits get stuck in rebar and eventually break. The question for a buyer is not “which concrete bit is strongest”, but which of three constructions the job needs.
- The edge stalls on the bar. A chisel-type 2-cutter edge meets a round bar, stops advancing and the bit jams.
- Carbide chips or the braze joint lets go. Repeated hammer blows on steel chip brazed inserts and overload the joint between insert and body.
- Heat builds up. Forcing a stalled bit on steel overheats the head and the braze.
Three Routes Through Rebar
Global brands now separate plain concrete bits from bits built to keep going through rebar, and from tools that only cut steel. Zhonghuan’s range follows the same three routes.
| Route | Head construction | Mode at the bar | What happens | Zhonghuan programs |
|---|---|---|---|---|
| 1. Concrete bit | 2-cutter (IZ, IR, I7); brazed 4-cutter cross | Hammer | Fast in plain concrete; a brazed 4-cutter tolerates incidental rebar contact, but on a bar you stop and switch | 2-cutter IZ SDS-Plus Ø5–16 mm; ZHPLUS-5X / 5R Ø5–25 mm; ZHMAX-5X Ø12–25 mm |
| 2. Full-carbide head | One-piece sintered carbide head, no brazed inserts | Hammer | Drills concrete and bar in one pass without a bit change | ZHPLUS-8 Ø4–25 mm; 3-cutter full-carbide SDS-Plus Ø3–20 mm; ZHMAX-8 Ø4–25 mm |
| 3. Rebar cutter | Hollow crown with carbide teeth | Rotation only, hammer off | Cuts the bar only; then you switch back to the hammer bit | SDS-Plus rebar cutter Ø12–32 mm |
The full-carbide route is what Bosch sells as EXPERT SDS plus-7X and SDS max-8X, Hilti as TE-YX and Diablo as Rebar Demon; Diablo states up to 7× the life of a standard 2-cutter. Four cutting edges are the common layout, but not the only one: one-piece 3-cutter heads are also rated for reinforced concrete, and we make them for small diameters. The rebar-cutter route is a different tool: Milwaukee states its SDS-Plus rebar cutters are for rebar only and up to 10× faster in rebar than a 4-cutter bit.
Above Ø25 mm a one-piece head is no longer practical, so large SDS-Max holes move to ZHMAX-7 (a full-width primary blade with two set-back side inserts, YG11C) for heavy reinforced concrete and deep holes, or ZHMAX-168 (three plates, six cutting edges, Ø22–45 mm) for round, straight holes in hard aggregate. Carbide grade supports the choice: YG8C (8% cobalt) on brazed standard heads, YG11C (11% cobalt, coarse grain) where toughness under rebar impact matters. See our Carbide Grade Selection Guide.
Zhonghuan Programs by Job
Start from the job and the diameter, then choose the construction. The shank follows the hammer: SDS-Plus for compact hammers, SDS-Max for heavier drilling.
| Job | Diameter | Program | Why |
|---|---|---|---|
| Plain or lightly reinforced concrete, masonry anchor holes | Ø5–16 mm | 2-cutter IZ SDS-Plus | Self-centering start, fast in plain concrete |
| Anchors and MEP fixings in reinforced concrete, incidental bar contact | Ø5–25 mm | ZHPLUS-5X (5R where tracking matters) | 4-cutter cross head; stop and switch if a bar blocks the hole |
| Rebar-heavy anchor programs, frequent bar hits | Ø4–25 mm | ZHPLUS-8 full-carbide head | Drills through rebar without a bit change |
| Small holes through bars or steel deck | Ø3–20 mm | 3-cutter full-carbide SDS-Plus | One-piece Y head, no insert joint to release |
| SDS-Max holes in rebar-heavy concrete up to Ø25 | Ø4–25 mm | ZHMAX-8 full-carbide head | One-piece head joined by resistance friction welding |
| Deep structural holes, bridges, heavy reinforcement | Ø16–45 mm | ZHMAX-7 multi-insert 4-cutter | Drilling speed and in-spec holes per bit |
| Round holes in hard aggregate, mining and rock | Ø22–45 mm | ZHMAX-168 6-cutter | Six impact faces for round, straight holes |
| A bar stops a brazed bit | Ø12–32 mm | SDS-Plus rebar cutter | Cuts the bar in rotation mode, then switch back |
Browse the SDS-Plus and SDS-Max ranges and the rebar cutters. Cutting a structural bar is always the structural engineer’s decision; locate bars with a scanner first, and never cut prestressing tendons.
Drilling Technique When You Meet Rebar
The right bit still needs the right handling. With a brazed bit, the rebar-cutter sequence below is the standard method; with a full-carbide head you keep drilling.
- Use hammer drilling for the concrete. The blows break the aggregate; rotation alone polishes and overheats the carbide.
- Start slowly, then go to full speed. Seat the head without walking, then let the hammer run at its rated speed.
- At the bar, follow the head you are using. Full-carbide head (ZHPLUS-8, ZHMAX-8): keep a steady feed and drill through. Brazed 2-cutter or 4-cutter: stop, withdraw, fit a rebar cutter of the same diameter, switch the hammer off, cut the bar, then return to the hammer bit.
- Clear the dust. On deep holes, withdraw the bit every 10–15 seconds or drill with dust extraction so the flutes do not pack.
- Never force a jammed bit. Release the trigger, reverse gently while rotating, and check whether you have hit a bar before you go on.
- Get the approval first. Scan for bars before drilling and follow the approved hole layout; cutting structural reinforcement needs the structural engineer’s approval.
More detail: Hit Rebar While Drilling Concrete? and How to Drill Through Rebar in Concrete.
Why Bits Fail in Reinforced Concrete
Most failures in reinforced concrete come from using the wrong route, not from a bad batch of carbide.
A plain 2-cutter where bars are frequent
It jams on the bar and chips; move rebar-heavy work to a full-carbide head.
Hammering a brazed head on steel
The insert chips or the braze joint lets go. Stop and use a rebar cutter instead.
Hammer mode on a rebar cutter
Hammer blows break the cutter’s teeth; Milwaukee even fits a protective shank against it. Rotation only.
Too much feed pressure
Force does not cut steel; it overheats the head and the braze.
Packed flutes
Without dust clearance the bit overheats and seizes in the hole.
Cost per Finished Hole
A cheaper bit costs more per finished hole once rebar is in the picture. Typical results for Ø8 × 80 mm holes in C25–C30 reinforced concrete:
| Construction | Typical holes per bit | Field reality |
|---|---|---|
| Low-cost 2-cutter | 8–15 | Jams and chips on bars, oval holes, frequent replacement |
| Brazed 4-cutter cross (ZHPLUS-5X) | 40–70 | Good in reinforced concrete; stop at a bar |
| Full-carbide head (ZHPLUS-8) | 80–120+ | Drills through bars, holds its gauge, fewest bit changes |
Count broken bits, re-drilled oval holes and the minutes lost changing bits, not just the unit price. For programs with frequent bar hits, the full-carbide head usually has the lowest cost per finished hole; we agree hole-count targets on your concrete during sample approval.
Sourcing and RFQ Checklist
For a distributor or contractor program, send:
- Diameters × working lengths and quantity per size
- Concrete class and rebar density, or the job type (anchors, MEP, structural)
- Hammer models and energy class
- The route mix: 2-cutter, brazed 4-cutter, full-carbide head, rebar cutter
- Benchmark bits (e.g. Bosch EXPERT 7X / max-8X, Hilti TE-YX, Diablo Rebar Demon)
- Packaging, marking and annual volume
We reply with a head-construction recommendation per SKU, sample and witness-drilling plan, and the quotation path.
Related Procurement Programs
If you are sourcing this product line for a distributor, importer, or private-label channel, these OEM and wholesale programs cover the procurement questions buyers usually 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…
- SDS-Plus Drill Bits for Anchor Bolt Installation in Concrete — Precision SDS-Plus hammer drill bits for mechanical and chemical anchor holes in concrete and masonry.
- SDS Plus Drill Bit Sets Private Label & OEM Packaging — Private-label SDS Plus drill bit set program for retailers, importers, and online tool brands: mixed masonry bits, chisels, plastic cases, blister cards, color …
Choose by rebar contact, diameter and machine
Compare full-carbide heads, six-cutter SDS-Max and the rotation-only rebar cutter by the task. Cutting structural reinforcement follows the approved project plan. Send diameter, working depth, hammer model and quantity for model advice and a quotation.
ZHPLUS-8 Full-Carbide Head
Our one-piece four-cutter carbide head keeps drilling through concrete and embedded rebar in hammer mode. RFW joins the complete head to the body for a continuous drilling workflow.
- Ø4–25 mm · total length 160–600 mm
- SDS-Plus · full-carbide head + RFW
- Rotation and hammer mode
ZHMAX-8 Full-Carbide Head
Our full-carbide SDS-Max program brings the one-bit rebar workflow to the SDS-Max platform. Match the bit diameter and working length to your hammer and target hole.
- Ø4–25 mm · total length 160–540 mm
- SDS-Max · full-carbide head + RFW
- Rotation and hammer mode
ZHMAX-168 Six-Cutter
Three carbide pieces form six cutting edges for larger reinforced-concrete holes and deep drilling. We configure this SDS-Max program around your aggregate, rebar, machine and working depth.
- Ø22–45 mm · total length 450 / 570 / 620 / 920 mm
- SDS-Max · three carbide pieces / six cutting edges
- YG11C-class carbide · 42CrMo body
SDS-Plus Rebar Cutter
Our carbide crown cuts the bar inside an existing concrete hole in rotation-only mode. After cutting the steel, switch back to the concrete bit to complete the hole.
- Ø12–32 mm · total length 150 / 300 mm
- SDS-Plus · rotation only, hammer off
- Cut the rebar, then return to the concrete bit
