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Half-Round Can Opener: Push the Cutter In and Twist

Seth P. Chapin, Atlantic, New Jersey · Public domain (expired patent)

أنشأه

Mary

6. أكتوبر 2026

Half-Round Can Opener: Push the Cutter In and Twist

Opening a sardine box or tin with a flat knife takes many strokes and leaves a ragged edge. Seth P. Chapin of Atlantic, New Jersey, received US 56,368, dated 17 July 1866, for an implement for opening sheet-metal cans and boxes: a cutter semicircular in section with sloping edges to a point, bevelled inside, on a handle; forced in nearly to the handle and twisted, it cuts a circle the size of its own curve, and a guard at its top keeps it in position and stops it going too deep. This rung works out how many twists a hole takes, then files the cutter from steel tube and opens a can.

مبتدئ

About 2 hours

التعليمات

Twists for a full circle

جارٍ تحميل دفتر Jupyter…

A cutter turned round before it

The embedded blueprint shears tin round a wheel. Chapin bends the blade into a half-tube so twisting it cuts a circle.

Read US 56,368

"The said edges a are beveled upon their inner side to make them sufficiently sharp, and the implement is used for cutting circular holes in the tin box by forcing it, point first, into and through the sheet metal nearly up to the end of the handle A, and then turning or twisting the cutter around by means of the said handle, which causes the foremost of the edges a to cut the thin metal in a circular line corresponding to the circle of which the back or convex side of the cutter forms an arc."

Cut the half tube

Cut 45 mm of 25 mm steel tube and saw it in half lengthwise. Keep one half.

المواد لهذه الخطوة:

أنابيب فولاذية إنشائية1 قطعة

الأدوات المطلوبة:

منشار حديد

ملزمة منضدة

قلم تعليم ثابت

مسطرة

Shape the point

File both long edges to slope in to a point at one end, over the last 25 mm. Bevel them inside with a round needle file and hone.

الأدوات المطلوبة:

مبارد (مبرد يدوي)

طقم مبارد إبرية

حجر شحذ

ملزمة منضدة

نظارة أمان شفافة

Guard and handle

Epoxy a large flat washer across the cutter's top as the guard, and a hardwood handle above it.

المواد لهذه الخطوة:

حلقة تثبيت مسطحة1 قطعة

أوتاد من خشب صلب1 قطعة

إيبوكسي ثنائي المكوّن1 قطعة

الأدوات المطلوبة:

ورق صنفرة

The build in 3D

FreeCAD model of this build, not of the patent: a 25 mm half-tube cutter with sloping edges to a point, the washer guard and the hardwood handle.

ملف التصميمBLENDCC0 - Free

تنزيل النموذج

Twist out a hole

Stand a sealed can on the kitchen scale. Force the point through the top until the guard meets it, then twist round; count the twists, read the peak load and measure the hole.

المواد لهذه الخطوة:

علبة صفيح1 قطعة

الأدوات المطلوبة:

ميزان مطبخ رقمي

قدمة رقمية 6 بوصات

ساعة إيقاف

قفّازات عمل جلدية

A cutter that will not enter, wanders or jams

Half-round can opener troubleshooting.

Flow

History and honest limits

**Seth P. Chapin** of Atlantic, Monmouth County, New Jersey, received US 56,368, dated 17 July 1866, for opening tin or other sheet-metal boxes in circles or straight or irregular lines. Widened at its widest part, the cutter cuts a larger part of a circle or oval at one thrust, leaving a piece easily bent over; another form has one edge flattened for sardine boxes, and a metal handle with a cross-piece for turning. Wyman's 1868 patent names it. **Honest limits.** A washer stands in for his guard, and the tube is unhardened. Your twist counts are the result.