Keyhole Buttonhole

Definition and Overview

A keyhole buttonhole is a buttonhole with a round opening at one end of a narrow slit, finished with stitching around the edge. Because the round part resembles a keyhole, it is also called a keyhole buttonhole. It is mainly used to allow a button shank or thickness to pass through smoothly.

“Eyelet” can also refer to an eyelet washer, which is reinforced by driving in a metal or resin ring, but a keyhole buttonhole is basically a buttonhole shape made by sewing. It differs from a metal eyelet in both structure and use.

Shape and Differences from a Closed-End Buttonhole

A keyhole buttonhole consists of a narrow section for the button to pass through and a round section that accommodates the shank or thickness. The round section helps buttons with a shank, thick buttons, cloth buttons, and similar types pass through more easily.

A closed-end buttonhole generally refers to a straight buttonhole with rounded ends. Closed-end buttonholes are often used for flat two-hole buttons and four-hole buttons, while keyhole buttonholes may be chosen for shank buttons and similar types.

• The length of the buttonhole is determined by considering the button’s passing size and the thickness of the textile.
• The size of the round section is checked by whether the button shank, cloth-covered portion, and maximum thickness can pass through smoothly.
• The stitching density and whether reinforcement is used are adjusted to match the thickness of the textile and the load during wear.

Main Applications

Keyhole buttonholes are seen on front openings and cuffs of jackets, suits, and coats, and are also used on thick shirts, vests, and fly extensions on pants. In particular, where shank buttons are used, both practicality and appearance are considered.

When finished with a hand-sewn look or made with thicker button thread, the outline of a keyhole buttonhole becomes more noticeable. In mass production, buttonholes are often made with a buttonhole machine, and specifications clearly state the shape, length, direction, and thread color.

Dimensional Notation and Specification Instructions

The size of a keyhole buttonhole itself is usually controlled by the overall length of the opening and the diameter of the round section, in mm. Button sizes may be shown in lignes as well as mm; one ligne is approx. 2.54 mm. Button dimensions and buttonhole dimensions are not the same, so they should not be confused.

When deciding specifications, the fit is checked using a test piece with the actual button and the outer fabric and interfacing layered together. In addition to the button’s outside diameter, the shank height, buildup from wrapping, and the thickness and stretch of the textile all affect the proper hole size.

How to Attach and Handling Notes

Mark the hole position after checking the grainline and finished front edge, and reinforce with interfacing as needed for stretchy or thick textiles. After buttonholing, a slit is cut, but cutting too far into the round section can damage the stitching thread or cause the hole to widen, so care is needed.

For washing or dry cleaning, fasten the buttons and place the garment in a laundry bag to reduce snagging and excess friction on the buttonhole area. When pressing, use a pressing cloth so the buttonhole thread and surrounding textile are not crushed, and use a temperature suitable for the button material.

• Check before and after wear for fraying, thread breakage, or stretching of the hole.
• Forcing an oversized button through can cause the buttonhole thread to break or the textile to tear.
• Unlike a metal eyelet, the keyhole buttonhole itself does not crack or discolor like metal.

Frequently Asked Questions

What is the difference between a keyhole buttonhole and an eyelet washer?

A keyhole buttonhole is a keyhole-shaped buttonhole with a rounded end made for passing a button through. An eyelet washer refers to a metal or resin ring used to reinforce a hole, or to a hole fitted with that hardware. The names are similar, but the components and uses are different.

Which buttons are keyhole buttonholes suitable for?

They are suitable for shank buttons, cloth buttons, thick buttons, and other buttons that need extra room for the shank or thickness to pass through. However, suitability is not determined by the button alone; the thickness of the layered outer fabric and interfacing, the strength of the buttonhole stitching, and how often it will be opened and closed must also be considered.

Should the length of a keyhole buttonhole be the same as the button diameter?

No. It is adjusted through prototyping based on the button’s shape, thickness, shank height, and the thickness of the textile, assuming the button must pass through. If it is too long, it may shift easily when closed; if it is too short, the buttonhole area will be under strain when opening and closing.