Quick Answer

Stop the drill the moment you feel the bit bite into rebar, reduce speed and feed pressure, and let the diamond segments grind through the steel slowly rather than forcing the rig. A standard wet core bit will glaze or wear fast on rebar; use a bit with a softer, more open bond designed for reinforced concrete, pull the bit out every 30–60 seconds to clear swarf, and never let the bit spin dry against the steel without water or air cooling.

Why Rebar Stops or Wears Your Core Bit

Rebar is high-carbon steel — far harder on diamonds than plain concrete. When a standard core bit designed for cured concrete hits steel, three things happen:

• Instant load spike: the rig stalls or the bit grabs, which can crack segments.
• Friction heat: steel does not fracture like concrete; it abrades the diamonds, and the heat burns the bond.
• Glazing: once the bond overheats it melts and re-coats the diamonds, so the bit stops cutting and just spins.

The fix is not a sharper bit — it is a bit engineered for steel-cutting, plus a drilling rhythm that keeps the diamonds cool and exposed.

How to Recognize You Have Hit Rebar

Sign	What it means
Cutting sound changes from gritty to a higher grinding pitch	Bit has touched a steel bar
Chips come out brown, not gray	Steel swarf, not concrete dust
RPM drops, drill body vibrates	Load spike — back off feed
Bit suddenly stops cutting even with pressure	Segments have glazed

Step-by-Step: Drilling Through Rebar

1. Reduce speed first. Switch the drill to a lower gear — roughly half the RPM used for plain concrete. Slower speed keeps the diamonds from overheating on steel.
2. Drop feed pressure. Let the bit cut on its own weight. Forcing the rig through rebar is the fastest way to lose segments.
3. Pull and clear. Every 30–60 seconds, withdraw the bit a few millimeters so cooling water or air can reach the contact zone and steel chips can escape.
4. Hold water flow. On a wet rig, keep the water valve open enough to carry chips away — dry grinding on rebar burns the bond in seconds.
5. Advance a few millimeters at a time. Once the cut sound changes back to gritty, you are through the bar and can resume normal feed.

Choosing the Right Core Bit for Reinforced Concrete

Plain concrete bits use a hard bond that holds diamonds deep. On rebar you want the opposite — a softer, more open bond that wears away quickly so fresh diamonds keep emerging. Our diamond core drill bits range includes wet bits (JOY-DCB-W) tuned for reinforced concrete, and replaceable core segments (JOY-CDS) so you can re-segment a worn tube instead of discarding the whole barrel. Tell us the rebar density and concrete strength on your RFQ — we will match the bond.

When to Switch Strategy

If you hit a thick bar (over 20 mm) or a dense rebar mat, do not fight it. Options: drill the rebar out with a short masonry bit first, mark the bar location and shift the hole, or — for structural holes — get the engineer to move the penetration. Pushing a core bit through a heavy rebar mat wastes more bits than the alternative costs.

Safety Tips

• Wear hearing protection, safety glasses with side shields, and cut-resistant gloves — steel chips fly.
• Never lean on the rig when the bit grabs; let the rig's torque limiter work.
• Anchor the rig to the floor or wall with a vacuum or bolt-down base. A wandering rig on rebar kickback can break your wrist.

Frequently Asked Questions

Q: Can I drill through rebar with a regular concrete core bit?

A: You can, but it will wear 3–5 times faster and may glaze. Use a reinforced-concrete bond or a dry bit rated for steel.

Q: Why does my bit stop cutting suddenly on rebar?

A: The bond overheated and glazed over the diamonds. Dress the bit on a concrete block, reduce RPM, and add water.

Q: Should I drill faster through rebar to get it over with?

A: No. Faster feed and higher RPM burn diamonds. Slow, light, wet is the fastest route through.

Q: How deep can I go in reinforced concrete in one pass?

A: Standard barrels are 350–450 mm. For deeper holes, drill a pilot first, then follow with a rebar-rated barrel.

Conclusion

Drilling through reinforced concrete is a rhythm, not a race. Slow down on the bar, feed light, keep the bit wet and clean, and use a bond matched to steel. Contact JOY TECH for a core bit recommendation matched to your rebar density and concrete strength — we ship from Xiamen worldwide.