Fasteners, nuts & bolts manufacturer.Proven metallurgy.

High-tensile and stainless steel industrial fasteners under the TUFF brand: hex and heavy hex bolts, nuts including heavy hex and all-metal lock nuts, TUFF interlock anti-loosening washers, DTI and hardened washers, tension control bolts, anchor and foundation bolts, shear connectors, U-bolts, studs, shafts, and special parts made to customer drawings.

Under ISO 898-1, an M16 coarse-thread bolt of class 10.9 must reach at least 163 kN (about 16.6 tonnes), with a proof load of 130 kN. Class 8.8 is 125 kN; class 12.9 is 192 kN. Use the calculator above for other sizes.

Each washer pair has cams on the inner faces, with a cam angle α larger than the thread pitch angle β. When vibration tries to rotate the bolt loose, the cams ride up and bolt tension rises instead of falling, so the joint locks itself.

A shear wrench turns the nut while holding the splined end. When the bolt reaches installation tension, the spline shears off at its groove. A missing spline shows the bolt is installed, so inspectors can check every bolt by eye. TUFF TC bolts carry the S10T head marking.

Our in-house laboratory is NABL-accredited to ISO/IEC 17025:2017. NABL is a signatory to the ILAC Mutual Recognition Arrangement, which supports recognition of accredited reports by other signatory bodies; acceptance for an order is subject to the purchaser's requirements.

DISGO® is a chrome-free, high-corrosion-resistance coating technology from Nihon Ruspert Co., Ltd., Japan. It is applied without causing hydrogen embrittlement, which makes it suitable for high-strength bolts.

TUFF bolts, nuts and washers are made from M8 up to M160, depending on the product and standard. Each product page lists the sizes we make. Non-standard parts are made to drawing.

Yes. Every lot is tested before dispatch to the applicable standard and the order's inspection plan, in our in-house laboratory accredited by NABL to ISO/IEC 17025:2017 for the tests in its scope.

Yes. Lots have been inspected on customer orders by agencies including TÜV SÜD, TÜV NORD, Lloyd's Register, DNV, SGS, BVQI, RITES and EIL.

In an independent test by Element Materials Technology, Singapore (report T24-56832R, November 2024), one TUFF M22 class 10.9 HSFG bolt reached 1,221 MPa tensile strength against the ISO 898-1 minimum of 1,040 MPa (17.4% above the minimum), with hardness 33.6 HRC and fracture in the free thread. This is one sample; results vary by size, grade and lot, and the test certificate of each supplied lot governs.

Under ISO 898-1, class 8.8 must reach 800 MPa tensile strength and 640 MPa yield up to M16 (830 and 660 MPa above M16). Class 10.9 must reach 1,040 MPa tensile and 940 MPa yield. The first number is one hundredth of the nominal tensile strength in MPa; the second gives yield as a share of tensile strength. 10.9 is quenched and tempered alloy or boron steel and is more sensitive to hydrogen embrittlement, so the coating has to be chosen with care.

ISO 898-2 pairs a class 10 nut with a 10.9 bolt, a class 8 nut with an 8.8 bolt and a class 12 nut with a 12.9 bolt. A nut of a higher class may always replace a lower one. The pairing makes the bolt break before the nut threads strip; thin nuts with reduced loadability do not give this assurance.

Proof load is the load a full-size bolt must carry without measurable permanent extension. It is the practical check of yield on a finished bolt. For class 10.9 the ISO 898-1 proof stress is 830 MPa; an M16 bolt therefore has a proof load of 130 kN.

ISO 898-1 requires hexagon bolts from M5 upward to carry the property class and the manufacturer's identification mark on the head. TUFF bolts are marked TUFF with the class, for example TUFF 10.9, so the bolt can be traced to its maker and checked against the test certificate.

ISO 10684 covers hot-dip galvanizing of fasteners from M8 to M64 up to class 10.9, with nuts tapped oversize after galvanizing. Parts of 320 HV hardness and above need controlled pickling to limit hydrogen. ASTM F3125 Grade A490 bolts must not be hot-dip galvanized.

Electroplating can introduce hydrogen into hardened steel. ISO 4042 calls for baking after plating, which reduces the risk but does not remove it. For 10.9 and 12.9 bolts, a non-electrolytic zinc flake coating to ISO 10683 avoids plating hydrogen; TUFF supplies zinc flake finishes, including DISGO®.

A 3.1 inspection certificate is issued by the manufacturer's authorised inspection representative, independent of production, and reports the actual test results for the lot. A 3.2 certificate is in addition validated by the purchaser's representative or a third-party inspector.

Check that the head marking (maker's mark and class) matches the test certificate and the heat number. Mechanical tests are hardness, proof load and wedge tensile to ISO 898-1 or ASTM F606. For structural assemblies, ask for the rotational capacity test of ASTM F3125 or the suitability test of EN 14399-2.