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Self-Closing Float Dasher Churn: Floats That Open to Churn and Close to Gather
Woody

Created by

Woody

6. October 2026NO
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Self-Closing Float Dasher Churn: Floats That Open to Churn and Close to Gather

Davis wanted one dasher that would churn "in the most effectual manner," then gather the butter and work out the buttermilk. Robert W. Davis of Rodgersville, New York, received US 7,233, dated 2 April 1850, for self-adjusting rotary churn-dashers. The dasher's fixed slats are set "at such angles as to force the cream toward the center"; movable floats hinged to its sides stand open when turning that way and move it outward, "which various and contrary motions so agitate it, that the butter is soon formed." Turned backward, the floats close on the slats so the outside forms "a uniform curve concentric to the axis," which throws the butter to the sides and bottom and presses it free of milk. This rung looks at the floats' swing, then prints the sides, slats and floats, assembles the dasher in a box, and makes butter.
Intermediate
About 4 hours, plus printing

Instructions

1

The floats' swing

Loading Jupyter Notebook...
2

A dasher that churns one way and gathers the other before it

The embedded blueprint reverses fixed paired blades to roll the butter up. Davis lets hinged floats change shape by themselves when the crank is reversed.
3

Read US 7,233

"In order to gather the butter and work it, the dasher is then turned in the contrary direction, and the movable slats then closing the outside of the slats of the dasher form a uniform curve concentric to the axis and moving with the convex side foremost. By a few revolutions of the dasher the butter is thrown from the center to the sides and bottom of the churn box, and these gathered into a roll."
4

Print the parts

Print two side pieces (/uploads/blueprints/self-closing-float-dasher-churn-side.stl), four fixed slats (/uploads/blueprints/self-closing-float-dasher-churn-slat.stl), four curved floats with hinge eyes (/uploads/blueprints/self-closing-float-dasher-churn-float.stl) and the crank arm (/uploads/blueprints/self-closing-float-dasher-churn-crank-arm.stl). Print in PLA at 0.2 mm layers, 30 % infill, 4 walls; wash before first use.

Materials for this step:

PLA FilamentPLA Filament1 piece

Tools needed:

FDM 3D PrinterFDM 3D Printer
5

Assemble the dasher

Slide the two side pieces onto a 10 mm square hardwood shaft 148 mm apart and screw the four slats between them. Hang each float between the arms' knuckles on a 3 mm stainless rod as its hinge, so it swings open one way and lies against its slat the other.

Materials for this step:

Hardwood DowelsHardwood Dowels1 piece
Mild Steel RodMild Steel Rod1 piece
Machine ScrewsMachine Screws1 piece
Wood GlueWood Glue1 piece

Tools needed:

HacksawHacksaw
Screwdriver SetScrewdriver Set
Hand SawHand Saw
6

The box

Take a food-safe box about 230 × 190 × 200 mm. Drill both ends on the axis 100 mm up, pass the shaft through with a leather washer at each end, and glue the crank arm and a dowel handle on.

Materials for this step:

Food-Grade Storage ContainerFood-Grade Storage Container1 piece
Leather StripLeather Strip1 piece
Wood GlueWood Glue1 piece

Tools needed:

Cordless DrillCordless Drill
Drill Bit SetDrill Bit Set
7

The build in 3D

FreeCAD model of this build, not of the patent: the box with one side off to show the dasher's side pieces, the fixed slats and the hinged curved floats, and the crank.
Design FileBLENDCC0 - Free
8

Churn forward, gather backward

Let the heavy cream stand until it reaches about 15 °C, checked with the thermometer. Pour in 1.5 litres. Crank forward, floats open; time until the butter comes. Then crank backward so the floats close and the round dasher gathers the butter into a roll; draw off the buttermilk and keep cranking to work it, as he did. Pour off the buttermilk, add cold water, churn a little and pour off again until it runs clear; work in a pinch of salt and weigh the butter.
Step 8 - Image 1

Materials for this step:

Heavy CreamHeavy Cream1500 ml
Coarse Sea SaltCoarse Sea Salt1 piece
WaterWater1 piece

Tools needed:

Leave-In Probe ThermometerLeave-In Probe Thermometer
StopwatchStopwatch
Digital Kitchen ScaleDigital Kitchen Scale
Stainless Steel Mixing Bowl (Large)Stainless Steel Mixing Bowl (Large)
9

Floats that won't open or close

Self-closing float dasher troubleshooting.

Flow

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10

History and honest limits

**Robert W. Davis** of Rodgersville, Steuben County, New York, received US 7,233, dated 2 April 1850. His drawing shows the dasher in a churn box with slats D strengthening it. He claimed "the self adjusting float or slat (C) which opens when churning the cream and closes of itself when the dasher is turned in the opposite direction to gather the butter." **Honest limits.** A food-safe box and printed parts stand in for his wooden box and dasher. FDM prints hold food in their layer lines, so wash well and replace when worn. Your times and weights are the result.

Materials

10

Tools Required

10

Design Files

1

CC0 Public Domain

This blueprint is released under CC0. You are free to copy, modify, distribute, and use this work for any purpose, without asking permission.

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