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Rose Engine Fly Cutter, Traditional

  
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Edge Angle

Sharpen the edge using a goniostat (or goneostat, if you prefer the Queen's English) to ensure the correct angle is maintained.

Sharpening with lapping compounds of 6, 3, 2, and finally 1 micron are recommended. The 1 micron paste should also used for resharpening via a micro bevel approach.

Additional honing information is in the Notes & Comments section below.

Considering the tools and machinery available in the 1800s, it is amazing such beautiful works were made. They must have been better machinists than we.

Rich Colvin

Some historical information about sharpening these is available on the Ornamental Turning Book of Knowledge.

General Guidelines

Usage

 α

Micro bevel

Sharp
ness

Comments
Hardwoods and Ivory-like Materials 60° - 65° 3° - 5°
8

This is recommended by Holtzapffel, but if the original angle is different, it is best to match that.

Higher angles are recommended for reducing chatter in the cutting operation.

Metal 70° - 75° 3° - 5°
8
 

Notes & Comments

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Examples of Historical Cutter Shapes

Historical Cutter Sharpening Method

With regards to sharpening, the method outlined by J.H. Evans in Ornamental Turning, Chapter VI (1903) is:

  1. Primary Bevel
    1. Use an oil stone
    2. Use a brass plate with oilstone powder and oil
  2. Secondary / Micro bevel (Evans recommended +3°)
    1. Use a brass plate with oilstone powder and oil
    2. Use a cast iron plate with very fine crocus powder and oil
  3. Debur - very lightly on the back side
    1. Use a cast iron plate with very fine crocus powder and oil

Newer Sharpening Tools

The Accu-Finish machine has been used for years by machinists. These machines use diamond wheels, or a ceramic lapping wheel with a diamond spray. It is is a really great machine, especially as it has a built-in goniostat, but it can be a bit expensive.

I've found the Tormek grinder to meet my needs, though I did have to make some of my own jigs.

Sharpness Scale

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Example icon

Sharpness scales (as shown in the grey icon to the left) are used to indicate the recommended sharpness for the blades noted above. You can click on any of the icons showing the sharpness scale and be redirected to the page describing this more. Lower numbers are duller; higher numbers sharper.

These are general recommendations; you will need to use your own judgment, based on the knive’s intended purpose.

More Information

Books & Papers

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