TVS HSFG Nuts, IS 6623 – M12 to M36, grades 8S and 10S

TVS Sundram Fasteners HSFG Nuts, IS 6623 are high strength friction grip nuts made by Sundram Fasteners Limited to IS 6623 / ISO 4775 / DIN 6915, in sizes from M12 to M36, property classes 8S and 10S, supplied in zinc phosphate and 4 plated or coated finishes (listed below). They are the mating nuts for HSFG bolts to IS 3757: heavy hex nuts with controlled hardness and accurate threads, so the bolt can be brought to its full preload without stripping. They are made by cold forging, with hot forging for the larger sizes.

This item is supplied at a price on request; tell us the sizes, pitch, property class and finish you need and we will quote.

Jai Enterprises is an authorised distributor of TVS Sundram Fasteners high tensile fasteners and supplies them from Bhilai and Raipur all over Chhattisgarh - Bhilai, Raipur, Durg, Korba, Bilaspur, Raigarh, Jagdalpur, Kanker, Ambikapur and every other district - and across India.

Is this the right one for you?

Check these four things before you order:

• Your thread is metric coarse pitch (M sizes).
• The size you need is within M12 to M36.
• The joint is a structural steel connection designed as a friction grip (slip-critical) joint, with the preload specified by the designer.
• You will tighten with a calibrated wrench, by the part-turn method or with load-indicating washers, as the design requires.

At a glance

• Brand: TVS Sundram Fasteners (Sundram Fasteners Limited, TVS group)
• Product: HSFG Nuts, IS 6623
• Standard: IS 6623 / ISO 4775 / DIN 6915
• Sizes: M12 to M36
• Form: hexagon
• Property class: 8S and 10S
• Material: Steel
• Surface finish: zinc phosphate, trivalent iridescent, trivalent white, hot dip galvanised and zinc flake coating (Geomet / Magni / Delta)
• Forging: cold forging, with hot forging for the larger sizes
• Price: price on request - tell us the sizes, pitch, property class and finish
• Supplied by: Jai Enterprises, Bhilai and Raipur - to every district of Chhattisgarh and across India, +91 9340081159

Specifications and dimensions

• Standard: IS 6623 / ISO 4775 / DIN 6915
• Material: high tensile steel; nut property classes 8S and 10S to IS 6623 / IS 1367-6
• Property class: 8S and 10S
• Surface finish options: zinc phosphate, trivalent iridescent, trivalent white, hot dip galvanised and zinc flake coating (Geomet / Magni / Delta)
• Manufacture: cold forging, with hot forging for the larger sizes
• Marking: TVS brand mark on the face and the property class mark
• M12: pitch 1.75; across flats 21.00 mm, across corners 22.78 mm, thickness 12.30 mm
• M16: pitch 2.0; across flats 27.00 mm, across corners 29.56 mm, thickness 17.10 mm
• M20: pitch 2.5; across flats 34.00 mm, across corners 37.29 mm, thickness 20.70 mm
• M22: pitch 2.5; across flats 36.00 mm, across corners 39.55 mm, thickness 23.60 mm
• M24: pitch 3.0; across flats 41.00 mm, across corners 45.20 mm, thickness 24.20 mm
• M27: pitch 3.0; across flats 46.00 mm, across corners 50.85 mm, thickness 27.60 mm
• M30: pitch 3.5; across flats 50.00 mm, across corners 55.37 mm, thickness 30.70 mm
• M36: pitch 4.0; across flats 60.00 mm, across corners 66.44 mm, thickness 36.60 mm
• Note: M22: across flats 36 mm (the printed table says 35.00; the across-corners figure and the IS 3757 bolt correspond to 36 mm)
• Source: SFL's technical product catalogue (September 2026 edition) and SFL's digital product catalogue; dimensions in mm

Why choose TVS Sundram Fasteners

• Made by Sundram Fasteners Limited, a TVS group company making high tensile fasteners since 1966: first Indian company with ISO 9000, IATF 16949:2016 certified, Deming Prize 2018 for 17 plants.
• Every lot is backed by a BIS, NABL and ISO/IEC 17025 certified laboratory - tensile, fatigue, torque-tension, salt spray and coating thickness testing - as described in SFL's technical product catalogue (September 2026 edition).
• Made to a named standard - IS 6623 / ISO 4775 / DIN 6915 - with the dimensions published in SFL's technical catalogue, so parts interchange with any other maker's to the same standard.
• The grade mark on each part shows its property class (8S and 10S), so site inspection is simple.
• A choice of finishes - zinc phosphate, trivalent iridescent, trivalent white, hot dip galvanised and zinc flake coating (Geomet / Magni / Delta) - from plain indoor use to hot dip galvanised and zinc flake coating for outdoor and corrosive service.

How to choose and fit

1. Use the complete set: IS 3757 bolt, IS 6623 nut (class 8S with an 8.8S bolt, class 10S with a 10.9S bolt) and IS 6649 hardened washer (35 to 45 HRC).
2. Bring the joint plates into contact (snug tight) before final tightening.
3. Tighten to the specified preload by the method the design states: calibrated torque wrench, part-turn of the nut, or direct tension indicators.
4. Do not reuse HSFG bolts that have been fully tensioned.

Where it is used

• steel bridges and flyovers
• industrial sheds, pre-engineered buildings and plant structures
• transmission towers and substations
• crane girders and conveyor galleries
• power plant and cement plant steelwork

Related products

• TVS Sundram Fasteners HSFG Bolts, IS 3757 - the other half of the HSFG set
• TVS Sundram Fasteners Plain Hole Circular Washers, IS 6649 - the hardened washer for HSFG sets
• TVS Sundram Fasteners Tension Control Bolt Assembly - tension control bolts for shear-wrench installation

Frequently asked questions

What is the price of HSFG Nuts, IS 6623?

It is supplied at a price on request. Send the sizes, grade, finish and quantity to Jai Enterprises on +91 9340081159 and we will quote from the current SFL list.

What goes with an HSFG bolt?

A matching HSFG nut to IS 6623 (class 8S with an 8.8S bolt, class 10S with a 10.9S bolt) and a hardened washer to IS 6649 (35 to 45 HRC). Jai Enterprises supplies all three.

Are TVS HSFG Nuts, IS 6623 available in Chhattisgarh?

Yes. Jai Enterprises, an authorised distributor of TVS Sundram Fasteners, supplies from Bhilai and Raipur all over Chhattisgarh and across India. Call +91 9340081159 or use the enquiry form.

Can I get a different finish or a non-listed size?

Yes. The standard finishes are zinc phosphate, trivalent iridescent, trivalent white, hot dip galvanised and zinc flake coating (Geomet / Magni / Delta); other finishes and sizes or lengths outside the range are quoted on enquiry from SFL.

How to order

Call Jai Enterprises on +91 9340081159 or send an enquiry with the sizes, pitch, property class, finish and quantity of HSFG Nuts, IS 6623 you need; they are supplied at a price on request. We supply from Bhilai and Raipur all over Chhattisgarh - Bhilai, Raipur, Durg, Korba, Bilaspur, Raigarh, Jagdalpur, Kanker, Ambikapur and every other district - and across India.