Core Drilling Tips:


For operator safety, most manufacturers recommend drilling over 67mm be done with the drill mounted in a stand.
- Ensure there are no power lines or water pipes where you are going to drill
- Always turn on the water (always use clean water) before turning on the motor. Otherwise the water jacket seals on the drill can overheat, which will cause them to leak.
- When the slurry changes colour (usually to gray) or the drill motor speed drops, you are most probably cutting steel. Drop the motor speed down and relax pressure by about 1/3. Some operators reduce water after exiting the steel to redress the blade again, but don't forget to turn the water up again afterwards.
- Similarly, if you are drilling concrete with a high strenth (or MPA), or with very hard aggregate in it, the bit may glaze up and need redressing. Do this by reducing the water by half for a few minutes, or by drilling into an abrasive material like limestone, a cinder block or similar.
- If your 127mm bit binds in limestone, United Diamond Tools have a limestone barrel specifically designed not to bind. We also sell 127mm bits with and without spirals, as well as 127mm bits for concrete and laterite.
- When removing the bit, turn the water down and back the bit out while the drill motor is still running.
- Waterproof grease on the drill spindle thread will make bit changing easier
- Always read your drill's operation manual before use
- Wear correct PPE (personal protective equipment)
- Use the drill and bits only in a safe manner as described in the operation manual.

Trouble Shooting:

Problem Cause Remedy
Loss of Segment   Bit is too hard, causing barrel to bounce Decrease drill speed, or use softer bond
Overheating Increase water flow
Drill not held rigidly allowing vibration Hold drill firmly, or mount drill on a stand
Segments crack  Bit is too hard Decrease drill speed, or use softer bond
Drill not held rigidly Hold drill firmly, or mount drill on a stand
Barrel Cracking  Too much pressure by operator Reduce pressure
Bit is too hard Use softer bond
Belled Barrel Too much pressure by operator Reduce pressure
Bit not cutting Too little pressure by operator causes the bit to glaze up  De-glaze bit (see above) then re drill with more pressure

Core Drill bits speeds:
(These core drill speeds are suggested only. Always consult your drill manual for recommendations to suit your machine)

Diameter mm Drill speed
8-29mm 3,000RPM
30-45mm 1,500RPM
46-65mm 1,200RPM
66-89mm 900RPM
90-125mm 600RPM
126-200mm 450RPM
201-400mm 300RPM

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