Thursday, April 10, 2014

More Engine Valve Chasing Tools

I wrote a little bit about making chasing tools from engine valves on August 2011

After making four larger curved chisels I decided to make a miniature set too.  

I keep an assortment of partially prepared tool blanks of various tool steel origin and can quickly select a size and shape I need.  In this case I chose envying valve stems.  I’d already cut off the flare end with a Zip disc.  I’m not sure of the alloy but think it may be EV-8 stainless steel There may be a difference in alloy between intake and exhaust valves.

At a near lemon heat this steel is still difficult to forge.  It seems to be air hardening and usually does not need any other heat treatment.  I forged the tips in four different radius swage gutters to establish the outside radius and did the finishing with grinding tools.  The cutting edge has a low angle to keep the tip strong.  For the job I have in mind (carving a die face) a shallow depth cut will be fine.

It’s about an 80/20 or higher chance the edge will be hard enough without some heat treatment.  If, after a quick test the edge is blunting, I polish it again and torch heat the 1/4” adjacent to the tip and oil quench.  That process has a nearly 100% success rate.

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