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Craft Knife: Doniger's Hinged Handle and Reversible Blade

Sundel Doniger · Public domain (expired patent)

أنشأه

Forge

26. أكتوبر 2026

Craft Knife: Doniger's Hinged Handle and Reversible Blade

A knife for model carving and fine cutting, by Sundel Doniger of New York, founder of X-Acto (US 2,463,682, filed 1945, granted 1949). The handle is two shell-like metal halves pivoted at the rear. A thin blade with a slot in its middle drops over a small 'staple' pressed out of one half; closing the other half pushes a tongue into the staple and locks the blade solid. Swing it open to change the blade or turn it end for end: the spare end rests inside the handle. The patent gives no sizes or metals. Mild steel sheet, the rivet, the spring steel blade and the sizes are ours. The picture: Figs. 1 and 2 of the patent.

متوسط

1 day

التعليمات

Mark out the two handle halves

Scribe two mirror-image halves, about 130 mm long, on mild steel sheet about 0.8 mm thick (ours). Give each a flat rear ear for the pivot and a nose at the blade end.

المواد لهذه الخطوة:

لوح فولاذ طري1 قطعة

الأدوات المطلوبة:

مخطاط

مسطرة

Cut and file the halves

Cut both halves out with tin snips and file the edges smooth.

الأدوات المطلوبة:

مقصّ صفائح

مبرد معادن

ملزمة منضدة

Dome the grip, keep the ends flat

Hammer the middle of each half into a shallow bulge over a hollow in a hardwood block. Leave the pivot ends flat, so the pivot cannot wobble, and leave the noses flat.

الأدوات المطلوبة:

مطرقة كروية الرأس

كتلة خشب صلب

Form the blade wall and its shoulders

On the mounting half (10), the nose is a flat wall (14) in the plane where the halves meet. Turn its top and bottom edges inward into shoulders (15, 16) just as far apart as the blade is wide.

الأدوات المطلوبة:

كماشة مسطّحة الفكّين

مطرقة كروية الرأس

ملزمة منضدة

Press out the staple

Slit the middle of the wall along two short parallel lines, lengthwise. Press the strip between the slits outward to form the staple (17).

الأدوات المطلوبة:

إزميل بارد

مثقب تعليم المركز

مطرقة كروية الرأس

سندان

Bend the locking channel

Bend the nose of the locking half (11) into a springy channel: a broad rear flange (19) about the size of the wall, and a front flange (20) with a tongue (21) and a cut-out (22) each side of it to clear the staple's legs.

الأدوات المطلوبة:

مقصّ صفائح

طقم مبارد إبرية

كماشة مسطّحة الفكّين

Drill the pivot

Clamp the halves together, punch the centre of the rear ear and drill through both.

الأدوات المطلوبة:

مثقب تعليم المركز

مثقب يدوي

ملزمة منضدة

Rivet the pivot

Rivet the flat ends together (Doniger used an eyelet; ours: a steel rivet). Close it firmly: the friction of the flat ends must hold the halves wherever you swing them.

المواد لهذه الخطوة:

برشام فولاذي1 قطعة

الأدوات المطلوبة:

مطرقة برشمة

سندان

Anneal and cut the blade blank

Soften a piece of spring steel strip about 0.4 mm thick (ours), as in the connected spring-steel blueprint. Cut a blank as wide as the gap between the shoulders.

المواد لهذه الخطوة:

شريط فولاذ نابضي1 قطعة

الأدوات المطلوبة:

كور الحدادة

كلّابة حدادة

رماد خشب صلب

مقصّ صفائح

قفازات لحام

Cut the centre slot

Cut a slot (18) in the exact middle of the blank that fits closely over the staple. Drill its ends and file out between them.

الأدوات المطلوبة:

مثقب تعليم المركز

مثقب يدوي

طقم مبارد إبرية

ملزمة منضدة

Shape both points

Cut each end of the blank to a slanting point, as in Fig. 1, and grind a cutting bevel at both ends.

الأدوات المطلوبة:

مقصّ صفائح

حجر سنّ دوّار

مبرد معادن

Harden and temper the blade

Harden the blade in oil as in the connected spring-steel blueprint. Temper it to the knife colour given in the connected heat-treatment blueprint, not to spring blue.

الأدوات المطلوبة:

كور الحدادة

كلّابة حدادة

زيت اللفت

قفازات لحام

Hone both edges

Hone both ends keen on the sharpening stone.

الأدوات المطلوبة:

حجر السنّ

Fit and lock the blade

Swing the halves open. Lay the blade flat on the wall, its slot over the staple and its edges between the shoulders. Swing the locking half shut: the tongue enters the staple and the channel grips the blade. No tools needed.

Reverse or change the blade

Swing the locking half up, lift the blade off the staple and turn it end for end, or fit a new one. The spare end sits protected inside the handle.

What the patent says, and what is ours

The patent fixes the parts and how they lock: hinged shell halves, flat riveted pivot ends that hold by friction, a wall with shoulders and a pressed-out staple, a slotted double-ended blade, a springy channel with tongue and cut-outs. It gives no sizes, no metals and no blade making. All sizes, the mild steel, the rivet and the spring steel blade are our choices. Doniger's better-known X-Acto knives hold the blade in a round collet instead.