Popular Woodworking 2005-06 № 148, страница 14

Letters

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when I came across the WoodRat. It does everything I had envisioned and more. I've had mine for three years now, and if all my tools were stolen, or destroyed, it would be one of the first things I would replace.

Randall Thomas Henderson, Nevada

Thoughts on High-speed Steel Chisels

The testing protocols devised by Christopher Schwarz for chisels ("High-speed Steel Chisels are Beyond Tough" February 2005) are objective and the results surprised me. In metal-working, high-speed steels, especially those alloyed with cobalt, often are brittle. I would have expected the edge to fracture in hard service as readily as a carbon-steel edge.

High-speed steels were originally devised to obtain "hot-hardness" (the ability to retain as-quenched hardness for hours) when working at temperatures that would draw the temper out of quenched carbon steels. There are different analyses of high-speed steel and, especially for industrial woodworking, certain analyses vary in their resistance to abrasion and even a type of dulling caused by steam and heartwood extractives at the cutting edge - more akin to accelerated corrosion than abrasion. High-speed steels really shine predominantly when hot-hardness is needed.

When a carbon steel chisel is sharpened on a grinder and the edge turns blue, the temper is drawn and that edge is ruined. Mr. Schwarz correctly points out that these high-speed steel chisels are designed for rough applications and I would like to point out that these chisels could be sharpened expeditiously on grinders and returned to service with the edge hardness unimpaired, even if discolored. I have done quite a bit of flooring and Victorian restoration, and these are two applications where I often had to do whatever it took, and unpleasant surprises go with the territory. These chisels could justify their premium price primarily where rapid return to serviceability after severe damage is necessary. PW

Cameron Brown Salem, Oregon

CORRECTION

In the "One-weekend Router Table" article (April 2005), the Milwaukee router we used was model 5625-20, not 5625-29 as stated in the text.

CIRCLE NO. 156 ON FREE INFORMATION CARD.

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Popular Woodworking June 2005