OpenSpecEngineering

Drawing callouts and matching hardware for SAE (inch) and metric screws from #0 to 1/2″ and M1.6 to M36. Pick a standard, a size and a thread, and the page gives the tap drill, the hole callout for every common feature in ASME Y14.5 [1] symbols, and the screws, washers, nuts and inserts that fit, by part number. Each callout has a Copy button for pasting straight onto a drawing.

What the page covers

• Tap drill for each thread pitch, for example a #7 drill (0.2010″) for 1/4-20 UNC.
• Clearance holes in close or free fit, from ASME B18.2.8 [3], with the nearest standard drill.
• Countersink, counterbore and spotface callouts for the clearance hole, with the 100° (MS24693 / NAS514) or 82° countersink angle.
• Tapped and blind tapped holes, written to ASME Y14.6 [2] with the thread class (2B for a standard internal thread) and depths.
• Helical coil (Heli-Coil) insert holes per NASM33537 [4] and the insert catalog [5]: the 3B insert thread, the entry countersink and, for blind holes, the full-thread and drill depths for inserts 1 to 3 diameters long.
• Parts: screws (socket head cap, pan, flat and hex head, and more), flat and lock washers, hex nuts and locknuts, and helical inserts in the selected size, with their MS, NAS or ISO part numbers [6]–[15].

Reading the callout symbols

⌀ is diameter, ⌵ a countersink, ⌴ a counterbore, ↧ a depth and SF a spotface. “THRU” means through the part. A value marked * was extrapolated beyond the source table, so verify it before machining. A dash means no reliable value exists for that size and feature.

Worked example

Spec a #4-40 socket head cap screw, 1/2″ long, with a flat washer. It passes through a close-fit clearance hole in a 0.28″ aluminum plate to thread into a blind helical coil insert.

1. Choose Standard SAE / Inch, Size #4 and Thread 4-40 UNC.
2. Under Clearance, choose Close Fit. The plate’s hole is: ⌀.116 ± .005 THRU
3. Under Blind Helicoil Insert, choose (for example) 1.5D (.168 in). The insert hole in the base is: .112-40 UNC-3B HELICAL COIL
   INSERT THD PER NASM33537
   FULL THD ↧.190 MIN
   TAP DRILL ↧.268 ± .010
   ⌵⌀.155 ± .015 X 120° ± 5°
4. In the parts card, set Fastener length to 1/2 and pick the parts:
   • Screw: NAS1352C04-8 (socket head cap, CRES 18-8).
   • Washer: NAS1149-CN432R (flat, 0.032″ thick).
   • Insert: NAS1130-04-15 (helical, 1.5D, 0.168″ long).

Check the stack-up. The screw reaches 0.500 − 0.032 (washer) − 0.280 (plate) = 0.188″ into the base. That engages the full 0.168″ insert and stops short of the 0.190″ full-thread depth, so the screw won’t bottom out. If the stack-up doesn’t fit, change the screw length or the insert length and read the parts again.