Rounded or Square Corner Hinges: Which One Fits Your Door?

Updated 2026-11-08 · RAYEN 雷茵

What is the difference?

Only the corners. On the drawings of our rounded hinges, the two outer corners of each leaf, the ones away from the knuckle, are rounded. The corners at the knuckle stay square. Height, width, thickness and knuckle can be identical to the square version.

The corners matter because of how the recess is cut. A router guided by a template cuts a pocket with round corners, the radius of the cutter. A rounded leaf drops straight in. A square leaf needs those corners cut square by hand first, or it sits proud. If the door is cut square, by chisel or on a machine that cuts square, a rounded hinge leaves small gaps at the corners.

Corners also change how the open door looks. A rounded leaf has no sharp corner at its free edge, so nothing catches a hand or a cleaning cloth, and the edge reads softer. On a square recess it looks wrong, though, so let the cut decide first and the look second.

What should you check before ordering?

• How the recess is cut: router with template, or square.
• The corner radius of that cut. Ask us for the hinge drawing and compare it, because the radius is not printed on our hinge pages.
• Leaf height and open width.
• Leaf thickness, for recess depth.
• Screw-hole positions, if the doors arrive pre-drilled.

Which rounded hinges are there?

• 3x3x2.5-2BB Rounded: 76.2 × 76.2mm, 2.5mm, Ø12.2mm, two ball bearings, stainless 304/201.
• 4x3x3.0-2BB Rounded: 101.6 × 76.2mm, 3mm, Ø14.2mm, two ball bearings, stainless 304/201. Its drawing shows rounded tips on the knuckle ends.
• 4x3x3.0-4BB Rounded: 101.6 × 76.2mm, 3mm, four ball bearings. In stainless the knuckle is Ø14.2mm, in Satin Sanded. In brass it is Ø12.7mm, in Frosted Copper.
• 5x3x3.0-4BB Rounded: 127 × 76.2mm, 3mm, Ø14.2mm, four ball bearings, stainless 304/201.

Which square hinge matches each rounded one?

This matters when one project uses both, or when you change from one to the other.

• 4x3x3.0-4BB Rounded in stainless matches 4x3x3.0-4BB in stainless: both 101.6 × 76.2mm, 3mm, Ø14.2mm.
• In brass they part company. The rounded brass hinge is 101.6 × 76.2mm with a Ø12.7mm knuckle. The square brass 4x3x3.0-4BB is 100 × 75mm with a Ø12mm knuckle. A recess cut for one does not fit the other.
• 5x3x3.0-4BB Rounded matches 5x3x3.0-4BB in stainless: both 127 × 76.2mm, 3mm, Ø14.2mm.
• 4x3x3.0-2BB Rounded has the same leaf, thickness and knuckle as 4x3x3.0-2BB US, but that square one has the US standard hole pattern. Compare the drawings before you swap them.
• 3x3x2.5-2BB Rounded has no square twin. The nearest square hinge, 3x2.5x2.5-2BB, is 76.2 × 63.5mm.

Every ball bearing hinge by size

The rounded hinges sit in the 76.2mm, 101.6mm and 127mm rows. Their codes end in the Chinese word for rounded.

A worked example

A door factory routes its doors with a template and wants a 4 × 3in hinge with four bearings, in stainless and in a brass finish for a second line. In stainless, 4x3x3.0-4BB Rounded fits the same 101.6 × 76.2mm pocket as the square stainless hinge, so the jig does not change. For the brass line, order the same model in brass and Frosted Copper. It keeps the 101.6 × 76.2mm leaf, but its knuckle is Ø12.7mm, so check the knuckle clearance on the frame. Ask us for the drawing, and set the router radius from it before the first run.

What should you write on the order?

• Full code with the word rounded.
• Leaf size in mm, thickness and knuckle.
• Material: stainless with grade, or brass.
• Finish: Satin Sanded, or Frosted Copper for the brass 4x3x3.0-4BB Rounded.
• Quantity, and the router radius you cut to.

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