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Crank-Point Can Opener: A Bent Point to Turn On, a Knife Set in a Slot
Samuel D. Lecompte, Leavenworth, Kansas · Public domain (expired patent)
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Created by

Forge

6. October 2026NO
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Crank-Point Can Opener: A Bent Point to Turn On, a Knife Set in a Slot

A can opened with a lever knife leaves a jagged hole of any size. Samuel D. Lecompte of Leavenworth, Kansas, received US 50,011, dated 19 September 1865, for an instrument for opening fruit and other sealed cans: a bar with a handle, its end bent like a crank and pointed so that, thrust through the top, the bent part is held by the edges of the hole as a bearing; a knife slides along a slot in the bar on a set screw, and the instrument is turned round to cut. This rung works out where to set the knife for each can, then forges the bar, crank and knife and cuts a round opening.
Intermediate
About 3 hours

Instructions

1

Knife position for each can

Loading Jupyter Notebook...
2

A lever opener before it

The embedded blueprint saws round a can with a lever knife. Lecompte gives the knife a centre to turn about and a slot to set its radius.
3

Read US 50,011

"The end of the instrument is bent somewhat in the form of a crank, and pointed, as shown by the letters b c in Fig. 1. This enables the instrument to be thrust into the top of the can in such manner that the part c, which is bent at right angles to the bar A, will be encircled by the edges of the hole made in the top of the can, thus insuring a good and sufficient bearing to enable the instrument to be operated."
4

Slot the bar

Cut 170 mm of 25 × 3 mm flat bar. Drill a row of 5 mm holes along its centre from 25 to 70 mm from one end and file them into a slot.

Materials for this step:

Mild Steel Flat BarMild Steel Flat Bar1 piece

Tools needed:

HacksawHacksaw
Bench ViseBench Vise
Center PunchCenter Punch
Cordless DrillCordless Drill
Drill Bit SetDrill Bit Set
Needle File SetNeedle File Set
RulerRuler
5

Forge the crank point

File the bar's slotted end down to 6 mm wide for its last 30 mm. Bend it down 15 mm, along 10 mm, and down again 15 mm in the vice, and file the end to a sharp point.

Tools needed:

Files (Hand File)Files (Hand File)
Bench ViseBench Vise
HammerHammer
Clear Safety GlassesClear Safety Glasses
6

Make the knife

Cut a 6 × 25 mm knife from 1 mm steel sheet with a pointed lower end and a 5 mm hole at the top. Hone its edge.

Materials for this step:

Mild Steel SheetMild Steel Sheet1 piece

Tools needed:

Tin SnipsTin Snips
Cordless DrillCordless Drill
Drill Bit SetDrill Bit Set
Files (Hand File)Files (Hand File)
WhetstoneWhetstone
7

Fit the knife and handle

Bolt the knife under the slot with an M5 screw, washer and nut as the set screw. Fit a hardwood handle to the bar's other end with epoxy.

Materials for this step:

Machine ScrewsMachine Screws1 piece
Flat WasherFlat Washer1 piece
Hex NutHex Nut1 piece
Hardwood DowelsHardwood Dowels1 piece
Two-Part EpoxyTwo-Part Epoxy1 piece

Tools needed:

Adjustable SpannerAdjustable Spanner
Cordless DrillCordless Drill
Drill Bit SetDrill Bit Set
8

The patent drawing

US 50,011 drawing sheet, public domain (expired patent).
Step 8 - Image 1
9

Cut a round opening

Set the knife for the can and tighten it. Stand a sealed can on the kitchen scale, thrust the point through the top's centre, press the knife in and turn round; read the peak load, time it, and measure the hole.
Step 9 - Image 1

Materials for this step:

Tin CanTin Can1 piece

Tools needed:

Digital Kitchen ScaleDigital Kitchen Scale
StopwatchStopwatch
Digital Caliper 6-InchDigital Caliper 6-Inch
Leather Work GlovesLeather Work Gloves
10

A point that tears out, a knife that slips

Crank-point can opener troubleshooting.

Flow

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11

History and honest limits

**Samuel D. Lecompte** of Leavenworth, Kansas, received US 50,011, dated 19 September 1865, for cans used for fruits, preserves and oysters. He did not limit himself to one knife shape, having adopted various styles. The patent was reissued on 4 February 1868 (No. 2,851). F. S. Wyman's 1868 patent names it as the circular opener he added a side knife to. **Honest limits.** A bolt and nut stand in for his set screw, and the knife is unhardened. Your loads and times are the result.

Materials

8

Tools Required

17

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CC0 Public Domain

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