How to Split Granite Rock

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Granite is split into blocks or slabs.
Granite is split into blocks or slabs. (Image: Photos.com/Photos.com/Getty Images)

Granite is a type of rock that can be sawed, but it is usually split. The process for splitting granite is similar in both the quarry and the stone yard. The principal difference is that quarries use dynamite while stone yards generally opt for a compound tool called a wedge and feathers. The wedge is a tapered steel spike and the “feathers” are concave shims that fit over the wedge. As wedges are hammered into the granite, the feathers expand and fracture the crystalline structure of the rock.

Things You'll Need

  • Straightedge or compass
  • Pencil
  • 3 Timbers (more, if necessary)
  • Masonry drill bit, 3/4-inch
  • Hammer drill, 2-inch
  • Stone tracer
  • Hand sledge or blacksmith’s hammer
  • Stonemason’s feathers
  • Stonemason’s wedges

Draw a line where you intend to split the granite with a straightedge (for straight splits) or a compass (for round splits).

Support the granite you want to split with three or more timbers. The number of timbers you will need depends on the size of your granite slab or block. Place timbers at least every 18 inches under the granite. Place one timber under the line you drew.

Scribe the line you drew with a stone tracer — a type of stone chisel with wide blade. Scribe the line by placing the blade of the tracer on the pencil line. Strike the butt of the tracer with a hand sledge or blacksmith’s hammer.

Drill holes every six inches along the line you drew. Drill the holes at least as deep as your wedges are long using a 3/4-inch masonry bit and a 2-inch hammer drill.

Place two stonemason’s feathers, concave side in, into each hole you drilled. Place one wedge between each of the two feathers.

Remove the timber support from under one side of the stone slab. Ensure that your feet are not under the unsupported stone.

Hammer all the wedges into the feathers using one strike on each wedge in succession along the entire split line. Continue to hammer until the granite splits.

Tips & Warnings

  • Removing the timber support from under one side of the stone slab allows one side of the split stone to drop as it breaks, adding gravity to the forces that break the stone.
  • Do not lubricate the drill bit with oil. Oil will stain the granite.

References

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