TVS Socket Countersunk Head Screws, inch UNC/UNF – 1/4" to 5/8", hardness 36 HRC minimum

TVS Sundram Fasteners Socket Countersunk Head Screws, inch UNC/UNF are 90-degree countersunk head screws with an internal hexagon drive, made by Sundram Fasteners Limited to BS 2470, in inch (UNC/UNF) sizes from 1/4" to 5/8", hardness 36 HRC minimum, supplied in zinc phosphate. The head sinks fully into a countersunk hole, so the surface stays flush - the choice for guards, covers, sliding parts and anywhere a projecting head would foul or catch.

SFL's retail price list of October 2026 gives recommended retail list prices from Rs 1,495 to Rs 10,265 per 100 pieces across the listed sizes; the exact price for your sizes, lengths, property class and finish is confirmed on enquiry.

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 inch UNC or UNF (American unified), not BSW/BSF.
• The size you need is within 1/4" to 5/8".
• The surface must be flush: you will countersink the hole at 90 degrees to take the head.
• The hardness (36 HRC minimum) suits the load; remember that a countersunk head carries less than a socket head of the same size.

List prices (SFL, 1 October 2026)

Prices are SFL's recommended retail list prices effective 1 October 2026, in rupees per 100 pieces, for the zinc phosphate (grey/black) finish, BS 2470 inch series. A few sizes are shown; ask us for any other size in the range. 7/16" is not on the list and is quoted on enquiry.

• 1/4" x 7/8" UNC: Rs 1,875 per 100 pieces
• 5/16" x 1-1/4" UNF: Rs 2,735 per 100 pieces
• 3/8" x 1-1/2" UNC: Rs 4,055 per 100 pieces
• 1/2" x 1-1/2" UNF: Rs 7,760 per 100 pieces
• 5/8" x 2-1/2" UNC: Rs 10,265 per 100 pieces
• BS 2470 inch series, special grade alloy steel, hardness 36 HRC minimum (SFL's data sheet: 36 to 45 HRC), all sizes fully threaded, zinc phosphate (grey/black) finish
• SFL forges these sizes against orders that reach its economic batch quantity - delivery is confirmed on enquiry

At a glance

• Brand: TVS Sundram Fasteners (Sundram Fasteners Limited, TVS group)
• Product: Socket Countersunk Head Screws, inch UNC/UNF
• Standard: BS 2470
• Sizes: 1/4" to 5/8"
• Head form: Countersunk Head
• Drive: Hexagon socket
• Thread: Fully Threaded
• Hardness: 36 HRC minimum
• Material: Steel
• Surface finish: zinc phosphate
• Forging: cold forging
• List price: Rs 1,495 - 10,265 per 100 pieces (SFL list, 1 October 2026); exact price on enquiry
• Supplied by: Jai Enterprises, Bhilai and Raipur - to every district of Chhattisgarh and across India, +91 9340081159

Specifications and dimensions

• Standard: BS 2470
• Material: alloy steel, hardened and tempered to 36 HRC minimum (BS 2470)
• Hardness: 36 HRC minimum
• Surface finish options: zinc phosphate
• Manufacture: cold forging
• Marking: TVS brand mark on the head
• 1/4": 20 UNC / 28 UNF tpi; socket across flats 4.03 mm (key 5/32"); head height 4.24 mm, head diameter 12.09 mm; lengths 3/8" to 2"
• 5/16": 18 UNC / 24 UNF tpi; socket across flats 4.83 mm (key 3/16"); head height 5.21 mm, head diameter 14.96 mm; lengths 1/2" to 2"
• 3/8": 16 UNC / 24 UNF tpi; socket across flats 5.63 mm (key 7/32"); head height 6.12 mm, head diameter 17.88 mm; lengths 5/8" to 2"
• 7/16": 14 UNC / 20 UNF tpi; socket across flats 6.43 mm (key 1/4"); head height 6.15 mm, head diameter 19.18 mm; lengths 5/8" to 2"
• 1/2": 13 UNC / 20 UNF tpi; socket across flats 8.03 mm (key 5/16"); head height 6.60 mm, head diameter 21.77 mm; lengths 3/4" to 2-1/2"
• 5/8": 11 UNC / 18 UNF tpi; socket across flats 9.63 mm (key 3/8"); head height 8.51 mm, head diameter 27.05 mm; lengths 1-1/4" to 2-1/2"
• Catalogue note: SFL's table prints a threaded length TL = 2D + 1/2" (example 1/4": 1"), while its price list says all sizes are fully threaded - confirm on enquiry for long screws
• Note: head heights as printed in the UNC/UNF table; the BSW/BSF table and SFL's socket data sheet give lower values for the same head (for example 2.87 mm for 1/4") - confirm when ordering
• Note: 5/8" key 3/8" (the 9.63 mm socket and SFL's price pages; SFL's suggested-keys table prints 5/16")
• 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 - BS 2470 - with the dimensions published in SFL's technical catalogue, so parts interchange with any other maker's to the same standard.

How to choose and fit

1. Pick the thread series and size from the drawing or the mating part: measure the diameter and pitch (or threads per inch) rather than guessing.
2. Countersink the hole at 90 degrees to the head diameter in the table so the head sits flush; the nominal length of a countersunk screw is its overall length, measured from the top of the head.
3. Supplied hardened and tempered to 36 HRC minimum (BS 2470); there is no grade choice.
4. Choose the finish for the environment: zinc phosphate for indoor or oiled use.
5. Tighten to the torque the design calls for; no washer goes under a countersunk head - use a washer under the nut only where the face needs it, and a nut of matching class.

Where it is used

• machine guards, covers and sliding ways
• tooling plates and fixtures
• hinges, handles and hardware
• equipment where a flush surface is required
• imported machinery and older plant built to inch standards

Other versions and series

• TVS Sundram Fasteners Socket Countersunk Head Screws, ISO 10642 metric - M3 to M20, list price Rs 615 - 28,705 per 100
• TVS Sundram Fasteners Socket Countersunk Head Screws, inch BSW/BSF - 1/4" to 5/8", list price Rs 910 - 10,265 per 100

Related products

• TVS Sundram Fasteners Socket Head Cap Screws, inch UNC/UNF - the standard socket head cap screw
• TVS Sundram Fasteners Hex Socket Keys, inch standard length - the keys that drive them

Frequently asked questions

What is the price of Socket Countersunk Head Screws, inch UNC/UNF?

SFL's recommended retail list price effective 1 October 2026 runs from Rs 1,495 to Rs 10,265 per 100 pieces across the listed sizes, for the zinc phosphate (grey/black) finish, BS 2470 inch series. The examples above show typical sizes. Call Jai Enterprises on +91 9340081159 with your sizes, grade, finish and quantity for the exact price; other finishes and sizes outside the list are quoted on enquiry.

Does the smaller head reduce the strength?

The head is smaller than a socket head cap screw's, so the screw should not be loaded to the full value of a socket head of the same size. Use the standard head where the full load is needed.

Are TVS Socket Countersunk Head Screws, inch UNC/UNF 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 finish is zinc phosphate; other finishes and sizes or lengths outside the list are quoted on enquiry from SFL.

How to order

Call Jai Enterprises on +91 9340081159 or send an enquiry with the sizes, lengths, property class, finish and quantity of Socket Countersunk Head Screws, inch UNC/UNF you need. SFL's list price is Rs 1,495 - 10,265 per 100 pieces across the listed sizes (SFL list, 1 October 2026); the exact price is confirmed on enquiry. 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.