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Hardening a "brush hog" mower blade to retain its strength and edge [Texas] 

July 27, 2007

I find that tough grass dulls the blades of my brush hog rather quickly. I have to pull them off quite often and put an edge back on them. They are approx 18" long with a thickness of 1/2" with a leading sharp edge. This application is on a farm tractor not your reqular garden mower.

Jim Roberts
Shady Springs Farm - Gilmer, Texas

Depending on the type of steel that the blade is made of, you may consider cryogenic treatment to extend the useful life of the blade. Cryogenic treatment of carbon steels has been shown to extend the operational life of cutting tools by as much as two to three times. After cryogenic treatment, the wear resistance of the steel is increased, therby enhancing the tool's ability to retain a sharp edge. Deep cryogenic treatment, or cold treating, is similiar to heat treating in that Time and Temperature produce Transformations in the steel. These include the formation of a uniform grain (or crystal) structure that eliminates voids and imperfections (of retained austenite) by creating a pure, homogenous crystal structue (of martensite). Additionally, the carbon structure is modified through the formation (or precipatation) of eta-carbides. Lastly, residual stresses, that propigate into cracks, are greatly reduced to eliminate many failures typically attributed as fatique failures. I recommend that you give it try. Not only will the blades stay sharper longer, but because of the reduced sharpening required, they will have a longer fuctional life. The cost of cryogenic treatment usually is low enough to provide a fast payabck, especially when you look at eliminating the down time and associated expense of re-sharpening, plus extended life of the tool.

Robin Rhodes Cryogenic Institute of New England, Inc. Worcester, MA