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Using Crackit: Hole Design

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Crackit only works as well as your hole layout. Diameter, spacing, and depth depend on the material, how much you need to remove, and whether you're pre-splitting or full demolition. Match the pattern to the job before you start drilling.

Planning your hole layout

Crackit hole design parameters

Hole layout comes down to bore diameter and the gap between holes. For diameters between 30 and 50 mm, spacing follows this rule:

A = K × D

Where A = spacing between holes (mm), D = hole diameter (mm), K = coefficient from the table below.

K value of rocks and concrete
Material to be cracked K value Steel contained (Kg/m3)
Soft virgin rocks 10 - 16 n/a
Medium hardness virgin rocks 8 - 12 n/a
Hard virgin rocks 5 - 10 n/a
Plain concrete 10 - 16 0 - 30
Reinforced concrete 8 - 10 30 - 60
6 - 8 60 - 100

Adjust K when the block shape or number of free faces changes

...
Fewer open faces → use a smaller K
...
More open faces → you can use a larger K
Cracking design reference chart
Material to be cracked Hole design parameters Crackit Consumption
(Kg/m3)
Diameter D (mm) Hole Spacing A (cm) Row Spacing R (cm) Hole Depth H (%)
Soft stone 35 - 40 40 - 100 (0.6 - 0.9) A 100% 5 - 10
Medium hard rock 38 - 42 30 - 40 (0.6 - 0.9) A 105% 12 - 22
Hard granite 38 - 42 25 - 40 30 - 80 105% 18 - 25
Rock cutting 30 - 40 20 - 40 (0.6 - 0.9) A 75% 12 - 18
Plain concrete 38 - 42 20 - 30 (0.6 - 0.9) A 80% - 85% 12 - 18
Reinforced concrete 38 - 50 15 - 30 (0.6 - 0.9) A 90% - 95% 18 - 25
...
Before your first test break, cross-check with our rock or concrete design pages for job-specific layouts.

How much Crackit to order

Once hole diameter, spacing, and depth are set, quantity is straightforward — add up the volume each hole will hold using the factor for your bore size:

C = Kg/m³ × Number of Holes × Depth of Holes

Rule of thumb: One 20 kg carton (44 lb) typically fills about 35 linear feet (~10 m) of 1½″ (38 mm) holes. You may not need every hole on some jobs.
Per bag: Each 5 kg bag fills roughly 8 ft of 1½″ hole or 11 ft of 1¼″ hole.

Kg/m³ values for different hole sizes and depth of 1 meter
Hole Diameter 30 mm 32 mm 34 mm 36 mm 38 mm 40 mm 42 mm 44 mm 46 mm 48 mm 50 mm
Crackit (Kg/m³) 1.2 1.3 1.5 1.7 1.9 2.1 2.3 2.5 2.8 3.0 3.2
Hole Depth One Meter
Note: Field conditions may reduce yield by 3–6% from chart values.
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