# Countersink hole A solid to cut a countersink and its clearance hole with, for a metric countersunk head screw whose head follows ISO 7721: for example ISO 10642 hexagon socket, ISO 2009 slotted and ISO 7046 cross recessed countersunk screws. Its axis is along Z, with its top face on the XY plane. The 90 degree cone runs from the countersink diameter Dc at the top down to the hole diameter d_h. The hole then runs down to the depth, measured from the top face. | Thread | d_h min. (nom.) | d_h max. | Dc min. (nom.) | Dc max. | t ≈ | |---|---|---|---|---|---| | M1.6 | 1.80 | 1.94 | 3.6 | 3.7 | 0.95 | | M2 | 2.40 | 2.54 | 4.4 | 4.5 | 1.05 | | M2.5 | 2.90 | 3.04 | 5.5 | 5.6 | 1.35 | | M3 | 3.40 | 3.58 | 6.3 | 6.5 | 1.55 | | M3.5 | 3.90 | 4.08 | 8.2 | 8.4 | 2.25 | | M4 | 4.50 | 4.68 | 9.4 | 9.6 | 2.55 | | M5 | 5.50 | 5.68 | 10.40 | 10.65 | 2.58 | | M6 | 6.60 | 6.82 | 12.60 | 12.85 | 3.13 | | M8 | 9.00 | 9.22 | 17.30 | 17.55 | 4.28 | | M10 | 11.00 | 11.27 | 20.0 | 20.3 | 4.65 | The model uses the nominal values, d_h and Dc min. (nom.), and the 90 degree angle. The cone's height is then (Dc − d_h) / 2. The table's t, the countersink depth, is given as approximate (≈) and isn't used; it is the depth at Dc max. ## Source ISO 15065:2005, *Countersinks for countersunk head screws with head configuration in accordance with ISO 7721*, first edition. Clause 3, Figure 1 (the 90° ±1° angle) and Table 1, "Dimensions of countersink", are on page 2 of the official preview: . Table 1's footnote a says d_h is ISO 273's medium series clearance hole, tolerance H13. ISO 15065 also lists tapping screw sizes ST2,2 to ST9,5 and a nominal size 5,5 for ST5,5 only; this recipe offers the metric threads. The depth of the hole is yours to set; it isn't part of the standard. ## Catalogue models The old catalogue's `countersink_clearance_M_cutter` entries (M2, M2.5, M3, M4, M5, M6, M8) name only the thread and have no model to measure. Each maps to this recipe's preset for that thread.