100 mm OD Flange, 45 mm Bore

A flat round flange, 100 mm outside diameter and 13 mm thick, with a 45 mm bore straight through the middle. Four 5 mm holes sit on a 72 mm bolt circle at 45°, 135°, 225° and 315°, countersunk from the top face and 10.5 mm across at the rim. The outer edges carry a 1 mm chamfer, so there is no sharp rim to catch on.

What it fits

• Bore: 45 mm nominal — measure the shaft, tube or spigot it goes over with calipers first. A printed 45 mm bore comes out undersized on most machines, so plan on reaming or drilling to size.
• Bolt pattern: four holes on a 72 mm bolt circle, at the diagonal positions rather than at 12/3/6/9 o'clock. Confirm the orientation of the mating part before drilling anything.
• Fasteners: 5 mm clearance with a countersink 10.5 mm across, sized around M5 flat-head screws so the heads sit at or just below the top face. Longer screws will not sit flush, and the 13 mm body sets how much thread you have to play with.
• Face: the 100 mm diameter leaves roughly 27.5 mm of material between the bore edge and the outer edge.

What it does not have

• No hub and no raised face — it is a plain flat disc, so it will not self-centre on a register.
• No thread, no taper and no keyway in the bore.
• No O-ring groove or gasket recess; sealing has to come from the mating faces or a separate gasket.
• No second bolt pattern — if the part you are mating to has six or eight holes, or a circle other than 72 mm, this will not bolt on.

Before you print

Measure the bolt circle and the hole positions on the part you are mating to, centre-to-centre, and check that the four-hole diagonal layout matches. Also check that 13 mm of thickness clears whatever sits behind the flange, since the countersinks eat into the top face and leave less material under the heads than a plain 13 mm plate would suggest.

Prints flat on the bottom face with no supports; the chamfer and the bore both come out clean laid down that way, and the countersinks form on the top surface without bridging.