When choosing an axe to restore, Brant & Cochran determines whether the axe bit has the requisite hardness to stand up to repeated, long term use. The steel at the bit edge on many newer axes and some older ones that were not properly cared for can be too soft to be of any use.
Steel can be graded using the Rockwell Hardness Scale. High quality axes sold today have steel with bits between 52-57 on the Rockwell Hardness Scale. Older axes may have considerably stronger steel in the 57-60 range. The steel at the poll may be significantly softer - around 45-50 on the Rockwell Hardness Scale.
Brant & Cochran uses hardness chisels to test the hardness at the bit of each axe it restores.
In some instances, axes which look fine to the naked eye have lost their temper either though excessive grinding when sharpening or being fired to remove a handle. Some are simply made with inferior steel. All restored axes sold by Brant & Cochran will have steel with a Rockwell hardness in the 52-60 range at the cutting edge.
Using hardness chisels
Thanks to Matt Parkinson @ Dragon's Breath Forge
For more information on hardening steel check out our blog post: