Quick Answer

To drill a 100mm hole through a 200mm concrete slab, use a 100mm wet diamond core drill bit on a core drilling machine anchored to the floor. Run the bit with constant water feed, drill straight down, and pull the core out with a chisel. A 100mm wet bit drills a 200mm slab in about 5-10 minutes in normal concrete depending on reinforcement.

Key Features You Need

• 100mm wet diamond core bit — matches your required hole diameter exactly.
• Core drilling machine with M16 or 1-1/4-7 UNC spindle connection.
• Anchor bolt, vacuum pad or screw anchor to hold the rig rigid.
• Water supply — hose or water tank with a valve adapter.

How to Drill a Slab Step by Step

• Mark the hole centre and check for post-tension cables or rebar with a cover meter.
• Anchor the core drill base firmly — a moving rig breaks bits and cuts oval holes.
• Start at low speed with light pressure until the crown bites a ring.
• Increase speed and feed steadily; let the segments cut, do not push hard.
• Maintain a constant water flow around the crown; stop if water runs out.
• When the bit breaks through, reduce feed and lift slightly to avoid grabbing the edge.
• Remove the core with a chisel or core removal tool.

How Long Does It Take?

Slab Thickness	100mm Wet Bit (normal concrete)	100mm Wet Bit (reinforced)
100mm	3-5 min	5-8 min
200mm	5-10 min	10-15 min
300mm	10-15 min	15-20 min

Safety Tips

• Check for buried services and reinforcement before drilling.
• Use a water collection ring or vacuum to manage slurry indoors.
• Wear ear and eye protection; core drilling is loud.
• Keep hands clear of the rotating bit and drill with both handles.

Frequently Asked Questions

Q: Can I use a handheld drill for a 100mm hole in a slab?

A: Not recommended — handheld core drilling is hard to keep square and dangerous at 100mm. Use a rig or a guide frame. Our core drill bits fit standard rig spindles.

Q: What if I hit rebar?

A: Slow the feed and let the diamond segments cut through the steel. Wet drilling keeps the bit cool. Avoid hammering the rig.

Q: Do I need a core longer than 200mm for a 200mm slab?

A:No — a 200mm long bit clears a 200mm slab. For deeper walls choose a longer bit or continuous threaded tube. See the continuous threaded tube drill for depth extension.

Conclusion

Anchor the rig, match the bit diameter to the hole, keep water flowing and control the feed — that is the whole recipe for a clean slab hole. JOY TECH supplies wet core bits, machines and adapters in bulk for contractors; contact us for OEM and volume pricing.