Granite Square 00 Grade 300 x 300 x 40mm - Precision Right Angle Square Block - 4 Hole

Solid black granite precision square, grade 00, for checking squareness and setting work at 90 degrees on a machine table or surface plate.

Granite square - 300 x 300 x 40 mm

A solid black granite square, 300 mm x 300 mm x 40 mm, for inspection and machine setup work. Granite square block (square type) with four through-holes for lifting and clamping.

Set the square on its reference face on a surface plate or machine table and bring the workpiece or the machine column up to the blade. Any deviation from 90 degrees shows as a gap at the top or bottom of the blade, which is why granite is used rather than steel: it does not rust, it does not burr when knocked, and it holds its shape through the temperature swings of a workshop far better than a steel square of the same size.

Specification

• Type: Granite square block (square type)
• Size: 300 x 300 x 40 mm (length x width x thickness)
• Material: black natural granite, fine grained, lapped working faces
• Grade: 00 (supplier stated)
• Stated accuracy: within 0.005 mm on the working faces (supplier stated, not certificate-verified)
• Working faces: ground working faces on the reference square
• Handling: four through-holes for lifting and clamping
• Packaging: wooden case (supplier stated)
• Lead time: 15 working days

What grade 00 actually means

The supplier states grade 00 with accuracy within 0.005 mm on the working faces. That figure comes from the supplier's own specification card, not from a calibration certificate - we have not verified it and we do not include a certificate with the item. Treat it as the supplier's claim, and if you need a documented accuracy for acceptance testing or customer sign-off, have it calibrated on arrival. We would rather say that plainly than print a tolerance we cannot stand behind.

Choosing the right size

A 300 x 300 mm square is the size you want when the feature being checked is roughly that tall. A square markedly smaller than the work only checks the bottom of it, and a square markedly larger is awkward to hold against a vertical face. Check the machine's own table size before ordering - on a small VMC a 300 mm blade can be taller than the working envelope you are trying to reach into.

Handling and care

Granite is hard and stable, but it chips rather than dents. Do not let it slide across a machine table with swarf under it, and never lift it by the blade - use the handling holes. Keep it in its case when it is not in use. Wipe the faces with a clean cloth before a check; a single chip of swarf under the face is bigger than the tolerance you are trying to measure.

What is and is not supplied

One granite square, 300 x 300 x 40 mm, in a wooden case. No calibration certificate or inspection report is supplied, and no stand or surface plate is included. The tolerance is the supplier's stated figure only.

Photographs

The two photographs show a square of this type from the same supplier range. They are representative of the product - the unit pictured is not the exact size listed here, and the size supplied is the size in the title. Granite is a natural material, so the colour and speckle of the stone will vary slightly from the photographs.