Heat treatment

[bigbob]

Hope you dont mind a small piece of advice when tempering or annealing your own blades. It's better to use a 'clean oil' rather than used sump oil as sump oil is full of impurities that can permeate the molecular structure of the blade and affect it, and when quenching a blade lower it point first into the warmed [ so as not to 'shock' the blade] oil bath as if it is laid in horiziontally it can 'pull' to the nearest side as it quenches.As a new member [ and old retired boily] of the site may I offer congratulations for some awesome knives on these posts.

[Steven J]

Welcome to the site Bob. Thanks for the tip. I have not made many knives, however any heat treating I have done has been quenched by laying the spine into the oil first. I have tried point first but still had distortions of the blade. When I was mucking about I generally used vegetable oil and found this fine for hardening file steel.

Steve

[bigbob]

When I said lowered into the oil bath i really should have said 'plunged' into it so the contractions caused by the molecular structure of the heated blade returning to a more normal unstressed state are uniformly acted on by the cooling process.Vegetable oil is okay for quenching as you say.