James NDT W-M-255 Low-Impact Manual Concrete Test Hammer

James NDT Low-Impact Concrete Test Hammer – field-test hammer for compressive strength of concrete specimens less than 4″ thickness, as well as hardness of other construction materials including ceramics, tile, and mortar, and rock core testing.

SKU: JAM-WM255 Category: Tags: ,


The W-M-255 Low-Impact Manual Test Hammer is a Type-L Rebound Test Hammer used for the non-destructive testing of hardened concrete for thin wall thicknesses. Easy-to-use W-M-255 provides immediate indication of concrete strength in various parts of a structure. The minimum verifiable strength is 1400 PSI (10 MPa) to approximately 9000 PSI (62 MPa). All concrete test hammers measure the surface hardness of the material they are testing; this is then correlated to concrete compressive strength.

James Low-Impact Test Hammer has a number of specialized applications. It is typically used for thin concrete specimens between 50 mm (2″) and 100 mm (4″) thick such as sidewalks, bridge decks and some driveways. The Type-L Rebound Hammer can also be used on plaster and mortar to verify material consistency, as wel as on brittle rock cores where a larger impact will damage the specimen. These units are commonly used to classify rock cores and brittle rock specimens.

The W-M-255 is also suitable for paper and film rolls where the higher impact energy of a standard test hammer will damage the surface of the material being tested. Typically eight to ten readings are taken across the surface of the paper or film roll to determine if the edges are as tightly wound as the center, and that winding has been even through out. TAPPI specifies readings 25 mm-75 mm ( 1″-3″ ) from the edge and 150 mm ( 6″ ) down the length of the roll. Rolls too loosely wound, or to soft will go out of round during shipment and storage. This will cause unwind speeds to be slowed thereby lowering productivity. Rolls that are wound too tightly hard can burst or tear during transport, and storage.

Also known as Schmidt Hammers or Swiss Hammers, all James Rebound Test Hammers conform to ASTM C-805, Standard Test Method for Rebound Number of Hardened Concrete, in addition to the following international standards:

Applications for the W-M-255:

  • Manual hammers for the quick and easy determination of the strength of concrete.
  • Lower impact energy for testing thin-walled specimens, below 100 mm ( 4 inches )
  • Ideal for testing small components
  • Ideal for testing rock cores, especially brittle rock
  • Paper roll and film testing

W-M-255 Low-Impact Test Hammer should be verified at regular intervals with W-C-7312 Test Anvil for calibrating James Test Hammers.

W-M-255 are supplied with carrying case and carborundum stone.