A live cross-section of the hole we machine. Pick 82° or 90°, the fastener, the sheet thickness, and whether the seat is on the top or the bottom. The diagram is the same view as the shop drawing — outer diameter, through-hole, thickness, and remaining land.
Calculator / 82° & 90°Xeon NC tooling tables
CSK / FLUSH SEAT
Inch screws
82°
Metric screws
90°
Min land
0.010″
Side
TOP OR BOTTOM
82°
ANSI / ASME B18.6.3
Standard for imperial flat-head machine screws. Default unless the drawing says otherwise.
90°
DIN 965 / ISO 10642
Metric flat-head screws. Do not mix a 90° screw into an 82° seat.
OD
Outer diameter
The major at the sheet surface. That is the number to dimension on the drawing.
LAND
0.010″ remaining
Thickness minus cone depth. Below 0.010″ the ring is a knife and the screw will not sit square.
The diagram is a through-thickness view of one countersunk hole. Change the angle, fastener, thickness, or side and the cone, through-hole, and remaining land update from our tooling tables.
Countersink Geometry
Cross-section view of a countersunk hole showing key dimensions
Angle
82°
Imperial flat-head (ANSI/ASME B18.6.3)
Outer Diameter
0.359″
Major at the sheet surface — dimension this
Side
Top (default)
Cone opens on the selected face
Through-hole
0.193″
Pilot / minor under the cone
Cone depth
0.095″
From the selected face
Remaining land
0.030″
Thickness minus depth. Floor 0.010″
Seat
FLUSH
Enough material under the cone
Numbers come from the same 82° imperial and 90° metric charts on the countersink guide and the countersinking service page. If remaining land drops below 0.010″, pick a smaller screw or a thicker gauge — a knife-edge seat burrs, deforms, and never sits square.
02 / How to Read It
Four dimensions. One seat.
The diagram is a slice through the hole. Everything you dimension on a drawing is on that slice.
THE FOUR CALLOUTSMATCH THE DRAWING
ANGLE
Included angle of the cone. 82° for inch flat-heads, 90° for metric. The tool, not a CAD default, sets this.
82° or 90°
OUTER Ø
Major diameter at the sheet surface. This is the circle you sketch in the DXF and the number in the hole table.
Major
HOLE Ø
Through-hole under the cone — the pilot the screw shank clears. Laser-cut, then the cone is milled on it.
Minor
THICKNESS
Sheet gauge. Depth is taken from this face. What is left under the cone is the land. Keep at least 0.010″.
Land ≥ 0.010″
03 / 82° vs 90°
Match the fastener, not the CAD default.
A 90° screw in an 82° seat bears on a ring. An 82° screw in a 90° seat does the same. The head will rock, sit proud, or chew the cone.
Use 82°
Inch flat-head screws
ANSI/ASME B18.6.3 — #4-40 through 5/16
Most US enclosure, rack, and audio hardware
Default at Xeon NC unless the drawing says 90°
Use 90°
Metric flat-head screws
DIN 965 / ISO 10642 — M2 through M8
European and aerospace callouts
Shallower cone than 82° at the same outer diameter
We do not run 100° or 120° as standard tools.Those angles show up as CAD defaults and as rivet seats. If the model is 100° or 118° (a drill point), it will not match a tool. Change it to 82° or 90°, or ask before you upload.
04 / Top or Bottom
The cone can open on either face.
Top is the default: the seat is on the cosmetic or mating face as the part sits in the nested sheet. Bottom puts the same cone on the opposite face so a screw can enter from the back of a panel.
The laser still cuts a square through-hole. The mill then plunges the cone from the selected side. Mark the face in the CAD feature and in the hole table — a countersink on the wrong side is a scrapped cosmetic panel.
Formed parts.Countersinks are milled while the blank is flat, before the brake. If a hole sits on a flange that will stand up, decide now whether “top” is the outside of the box or the inside. The calculator side toggle is that decision.
05 / Call It Out
One hole note. No conflicting depths.
Give the mill a through-hole, an outer diameter, an angle, and a side. Do not also drive depth unless you mean it to override the table.
01
Model the through-hole, then the cone.
Use the minor from the calculator as the laser hole. Apply a countersink feature at 82° or 90° to the tabulated outer diameter.
0.193 THRU, CSK 0.359 × 82°
02
Name the side.
NEAR SIDE or FAR SIDE, or TOP / BOTTOM as the part is nested. If the cosmetic face is film-side, say so.
03
Keep 0.010″ of land.
If the calculator shows a warning or a fail, drop a screw size or go up a gauge. A flush head on a knife-edge ring will not stay flush.
