ENGINEERING TOOL · ANSI / IMPERIAL
ANSI countersunk-head screw hole calculator
Look up verified 82° flat-head machine-screw dimensions and calculate a conservative ideal countersink envelope from the drawing's minimum finished hole.82° FLAT-HEAD MACHINE SCREWS
Drawing hole in. Conservative ideal envelope out.
IDEAL 82° COUNTERSINK AT PART SURFACEØ0.390051 inØ9.908 mm
Back face clearREAD THE 2D SECTIONSurface mouth → 82° taper → finished through-hole
Follow the centerline from the part surface to the back face. Orange dimensions are calculated; blue dimensions come from the drawing.
LIVE 2D SECTION VIEWIdeal 82° countersink · axial cross-section
GEOMETRY ONLY · NOT TO SCALE1Surface mouthØ0.390051 in
282° taper depth0.108739 in
3Drawing through-holeØ0.201 in
4Back-face status0.016261 in clear
Two-dimensional axial section: surface mouth Ø0.390051 in tapers at 82° to the drawing's Ø0.201 in minimum finished through-hole after 0.108739 in; 0.016261 in remains to the back face. The screw is intentionally omitted.
Actual head A0.333–0.362 in
H reference0.116 in
F max at G0.042 @ Ø0.313 in
Head angle80–82°
THICKNESS CHECK0.016261 in remains
Based on the entered 0.125 in part thickness.
READ THE RESULT CORRECTLY
Fastener data is standardized. The production hole still belongs to the drawing and process plan.
Enter the hole's lower limit
The engine uses the smallest permitted finished through-hole because it creates the deepest head envelope. G is a protrusion-gage diameter, not a clearance-hole recommendation.
Use the 80° head worst case
The permitted head angle is 80–82°. The steeper 80° head surface controls the conservative extension from published F max at G to the entered hole.
Add manufacturing policy separately
The displayed 82° cone is ideal and sharp-edged. Tool flat or radius, runout, deburring, seating requirement and inspection tolerance require drawing-specific allowance.
STANDARD SCOPE
One verified fastener family—kept separate from look-alikes.
Head data covers #0000 through 3/4 in. The three miniature slotted sizes remain reference-only because the standard provides no practical F/G protrusion-gage values.
Calculable sizes support slotted, cross-recessed Type I and cross-recessed Type IA selections without changing the shared external head envelope.
Flat socket cap screws use a different dimensional family and head-angle range. They require their own verified table before being added.
VERIFIED REFERENCE BASIS