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ISO 7051 Countersunk (Flat) Head Tapping Screws with Cross Recess (Form C)

ISO 7051 countersunk (raised) head tapping screws with cross recess, Form C — ST2,2 to ST6,3 — the flush power-tool head with a low crown, with the collected f/rf crown rows, recess sizing and Type H/Z driving ladders.

Last updated: 2026-11

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ISO 7051 Countersunk (Flat) Head Tapping Screws with Cross Recess (Form C) in an industrial setting
Illustrative image redrawn from real product references — not a photograph of stocked items.

Specifications

ISO 7051 completes the cross-recessed tapping trio: a countersunk body with the shallow raised crown — the source titles it "Countersunk (Flat) Head", and the raised portion is what the f and rf rows carry (f approx. 0,7 → 2 mm; rf approx. 3,8 → 11,1 mm). You get flush mounting with a slightly proud driver-friendly button that survives paint and panel distortion better than a true flush slot. The collected ladder runs ST2,2 to ST6,3: head diameter dk nominal=max./min. (4,3/4 up to 12,4/11,97 — identical to the flush member's ladder), approximate heights k and f, edge radius r, crown radius rf, the cross-recess No. ladder (1/1/2/2/2/2/3/3), and the Type H/Z driving rows with m depth gauges and "Penetration deptd" min./max. limits (the source's label carried verbatim). The length ladder l 6,5 to 38 repeats the flush member's verbatim quirk — the l = 38 row printed twice with mass cells starting at ST5,5 then at ST4,8 — flagged in the table note, both rows kept. The deep slot (t in the driving rows) rides the crown the same way the slotted raised member's does. Property class, material and finish are not tabulated — per RFQ.

Standard ISO 7051 — countersunk (flat) head tapping screws with cross recess, Form C
Size range ST2,2 – ST6,3; parenthesised (ST3,9) is the source's non-preferred marking
Raised crown f approx. 0,7 → 2 mm; crown radius rf approx. 3,8 → 11,1
Head diameter dk nominal=max. 4,3 → 12,4 mm (min. 4 → 11,97)
Cross recess No. 1 (ST2,2/ST2,9), No. 2 (ST3,5–ST4,8), No. 3 (ST5,5/ST6,3)
Recess driving data Type H m approx. 2,8 → 7,4 / Type Z m approx. 2,4 → 7,1; penetration min./max. per size
Length ladder l 6,5 – 38 with approximate mass per thread; source prints the l = 38 row twice (flagged verbatim)
Material / finish Not tabulated by the collected specification — per RFQ
ISO 7051 countersunk (flat) head tapping screws with cross recess, Form C - attribute rows per thread size (ST2,2 - ST6,3)All dimensions in millimetres. Attribute labels follow the source: P = thread pitch, a = thread end length, dk = head diameter (nominal = max.), f = raised portion height (approx.), k = head height (approx.), r = countersink edge radius, rf = raised-crown radius, Cross recess No. = recess size; Type H / Type Z carry the source's own labels m (recess depth gauge, approx.) and "Penetration deptd" (min./max.) verbatim; y = thread-end shear allowance by tapping-screw type.
AttributeLimitST2,2ST2,9ST3,5(ST3,9)ST4,2ST4,8ST5,5ST6,3
P0,81,11,31,31,41,61,81,8
amax.0,81,11,31,31,41,61,81,8
dknominal=max.4,35,56,87,58,19,510,812,4
dkmin.45,26,447,147,749,1410,3711,97
fapprox.0,70,91,21,31,41,51,72
kapprox.1,31,72,12,32,533,43,8
rmax.0,81,11,41,51,61,92,12,4
rfapprox.3,84,65,466,68,29,411,1
Cross recessNo.11222233
Type H mapprox.2,83,44,64,74,95,477,4
Type H Penetration deptdmin.1,171,811,892,042,242,73,023,46
Type H Penetration deptdmax.1,572,212,392,542,743,23,533,96
Type Z mapprox.2,43,14,34,44,65,16,67,1
Type Z Penetration deptdmin.1,11,831,8822,262,692,923,4
Type Z Penetration deptdmax.1,352,082,342,462,723,153,383,86
y max.Type C22,63,23,53,74,356
y max.Type F1,62,12,52,72,83,23,63,6
ISO 7051 thread length ladder - nominal/min./max. by type with approximate mass per thread (l 6,5 - 38)All dimensions in millimetres; the merged source header rows are rendered into the column labels. l limits: Type C min./max. and Type F min./max. Mass columns carry the source's own header verbatim: "Approximate mass (7,85 kg/dm3), per 1000 units in kg", blank where the source shows no mass. The source's Table 2 header omits the thread-size row; the mass columns run ST2,2 → ST6,3 left-to-right per Table 1's thread order.
l nominalType C min.Type C max.Type F min.Type F max.ST2,2ST2,9ST3,5(ST3,9)ST4,2ST4,8ST5,5ST6,3
6,55,77,35,76,50,180,332
9,58,710,38,79,50,240,440,7210,8881,071,53
1312,213,812,2130,310,5660,8981,111,321,882,743,46
1615,216,815,2160,370,6741,051,31,532,183,124
1918,219,818,2190,7821,21,491,742,483,514,54
2221,222,820,7221,351,681,952,783,895,08
2524,225,823,7251,511,872,163,084,285,62
3230,733,330,7322,653,785,196,88
3836,739,336,7385,977,96
3836,739,336,7384,526,458,82
  • Row 10 (38): The source prints the l = 38 row twice — first with mass cells from ST5,5 only, then again with mass cells from ST4,8. Both rows carried verbatim (row indices 8 and 9 here), not de-duplicated.

Materials

  • Material and finish specified per RFQ — state host sheet thickness (crown + cone both need metal) and finish; case-hardened steel is the standard tapping body

Ordering & documentation

Documents

Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.

Quotation

  • The fastener family (ISO 7051 Countersunk (Flat) Head Tapping Screws with Cross Recess (Form C)) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
  • Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
  • Quantity per size and your target delivery date.
  • Destination country, and any required documents (for example a mill test certificate) so the quote includes them.

Sample & supply

Minimum order quantity is 10,000 pieces. Stock items run 3–7 days. Quantities or variants outside the standard range are confirmed at quotation.

Storage & shipping

Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.

Frequently asked questions

The source titles this "Countersunk (Flat) Head" — where is the raise, and which standard do I spec?

In the f and rf rows. The title is the source's own (carried verbatim in the table caption); the collected geometry makes the distinction concrete: f approx. 0,7 → 2 mm of crown above the cone, blended by rf 3,8 → 11,1 — rows the flush ISO 7050 does not carry. So the practical spec question is the same as within the slotted pair: flush and nothing proud → ISO 7050; flush seating plus a driver-friendly button → ISO 7051. The two share the identical dk ladder (4,3 → 12,4), the same recess numbers (1/2/3), and the same Type H/Z driving-row structure, so the hole prep and driver sizing transfer directly. Two verbatim capture quirks are flagged on this batch: the duplicated l = 38 mass row (documented in the table note, values agreeing where they overlap) and the source's "Penetration deptd" label. Neither touches head or thread geometry. Material, class and finish stay per RFQ on the whole trio.

Related knowledge

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What to include in your inquiry

  • ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
  • ✓ Sizes, lengths and thread type (metric or inch).
  • ✓ Quantity per size and your target delivery date.
  • ✓ Destination country, plus any coating or finish requirement.
  • ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
  • ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
  • ✓ Factory-direct pricing
  • ✓ Standard and custom specifications
  • ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
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