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Craft Knife: Doniger's Hinged Handle and Reversible Blade
English
Sundel Doniger · Public domain (expired patent)
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26. Ukwakira 2026NO
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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.
Hagati
1 day

Amabwiriza

1

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.

Ibikoresho by'iyi ntambwe:

Urupapuro rw'icyuma cyoroshyeUrupapuro rw'icyuma cyoroshye1 igice

Ibikoresho bikenewe:

Igikoresho Gishushanya ImirongoIgikoresho Gishushanya Imirongo
Umurongo w'ipimaUmurongo w'ipima
2

Cut and file the halves

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

Ibikoresho bikenewe:

Ibyuma bikata ibyuma bisanzweIbyuma bikata ibyuma bisanzwe
Ikariso ry'IcyumaIkariso ry'Icyuma
Ifatiro ry'AmezaIfatiro ry'Ameza
3

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.

Ibikoresho bikenewe:

Inyundo ifite umutwe wa burutaInyundo ifite umutwe wa buruta
Igihimba cy'Igiti GikomeyeIgihimba cy'Igiti Gikomeye
4

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.

Ibikoresho bikenewe:

Ipfundo Rifite Umunwa UringaniyeIpfundo Rifite Umunwa Uringaniye
Inyundo ifite umutwe wa burutaInyundo ifite umutwe wa buruta
Ifatiro ry'AmezaIfatiro ry'Ameza
5

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).

Ibikoresho bikenewe:

Ishoka ry'icyuma gikonjeIshoka ry'icyuma gikonje
Igicukuzi cyo Gushyira IkimenyetsoIgicukuzi cyo Gushyira Ikimenyetso
Inyundo ifite umutwe wa burutaInyundo ifite umutwe wa buruta
IngoyiIngoyi
6

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.

Ibikoresho bikenewe:

Ibyuma bikata ibyuma bisanzweIbyuma bikata ibyuma bisanzwe
Ikusanyirizo ry'Amakariso MatoIkusanyirizo ry'Amakariso Mato
Ipfundo Rifite Umunwa UringaniyeIpfundo Rifite Umunwa Uringaniye
7

Drill the pivot

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

Ibikoresho bikenewe:

Igicukuzi cyo Gushyira IkimenyetsoIgicukuzi cyo Gushyira Ikimenyetso
Igikoresho cyo gutobora gikoreshwa n'intokiIgikoresho cyo gutobora gikoreshwa n'intoki
Ifatiro ry'AmezaIfatiro ry'Ameza
8

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.

Ibikoresho by'iyi ntambwe:

Utuma tw'icyumaUtuma tw'icyuma1 igice

Ibikoresho bikenewe:

Inyundo yo gushyira rivetiInyundo yo gushyira riveti
IngoyiIngoyi
9

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.

Ibikoresho by'iyi ntambwe:

Umurongo w'icyuma cya sipringiUmurongo w'icyuma cya sipringi1 igice

Ibikoresho bikenewe:

Iziko ryo GucuraIziko ryo Gucura
Amakoro y'UmucuziAmakoro y'Umucuzi
Ivu ry'Igiti GikomeyeIvu ry'Igiti Gikomeye
Ibyuma bikata ibyuma bisanzweIbyuma bikata ibyuma bisanzwe
Uturindantoki two gukomeza ibyumaUturindantoki two gukomeza ibyuma
10

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.

Ibikoresho bikenewe:

Igicukuzi cyo Gushyira IkimenyetsoIgicukuzi cyo Gushyira Ikimenyetso
Igikoresho cyo gutobora gikoreshwa n'intokiIgikoresho cyo gutobora gikoreshwa n'intoki
Ikusanyirizo ry'Amakariso MatoIkusanyirizo ry'Amakariso Mato
Ifatiro ry'AmezaIfatiro ry'Ameza
11

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.

Ibikoresho bikenewe:

Ibyuma bikata ibyuma bisanzweIbyuma bikata ibyuma bisanzwe
Ibuye ryo gutyaza ry'uruzigaIbuye ryo gutyaza ry'uruziga
Ikariso ry'IcyumaIkariso ry'Icyuma
12

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.

Ibikoresho bikenewe:

Iziko ryo GucuraIziko ryo Gucura
Amakoro y'UmucuziAmakoro y'Umucuzi
Amavuta ya kolzaAmavuta ya kolza
Uturindantoki two gukomeza ibyumaUturindantoki two gukomeza ibyuma
13

Hone both edges

Hone both ends keen on the sharpening stone.

Ibikoresho bikenewe:

Ibuye ryo gutyazaIbuye ryo gutyaza
14

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.
15

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.
16

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.

Ibikoresho

3

Ibikoresho bikenewe

21

Iki gishushanyo gikora

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CC0 Umurenge rusange

Iyi blueprint yasohowe munsi ya CC0. Ushobora gukoporora, guhindura, gukwirakwiza no gukoresha nta kwemererwa.

Shyigikira Umuremyi ugura ibicuruzwa binyuze muri Blueprint ye Komisiyo y'Umuremyi byashyizweho n'Abacuruzi, cyangwa kora verisiyo nshya y'iyi Blueprint ukayinjiza nk'isano muri Blueprint yawe kugira ngo musangire inyungu.

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