QUESTION ON 52100 AND 416 SS San Mai


I have an unlimited supply of rollers from Timken roller bearings. They are about 1 1/2 in in diameter and about 2 inches long and are just the perfect size for knife blanks and other things. I have used them with 15N20 and they make great Damascus, recently I have been using them for the center core in my San Mai.
After forging and running the rollers trough my rolling mill I let them cool in vermiculite. I can then cut when with a band saw or drill holes in them. Sometimes it is tough cutting and drilling, but doable.

When I use this stock to make my San Mai after forging I also put the billet in vermiculite to let it slow cool. I have been able to cut it however it is really slow and hard on saw blades. As for drilling, forget it. As soon as you drill through the 416SS and hit that 52100 center core it just takes the edge right of a HSS drill bit and it is impossible to drill.
I now have a set of 1/8,3/16 and 1/4 carbide bits. It is the only way to get hole through this stuff.

I would have thought that coating the 52100 with the 416 SS and putting it in vermiculite should slow down the cooling of the 52100 and if anything make it a bit softer and easier to work with.

Any help or solutions to this problem would be much appreciated.


Kevin R. Cashen

Super Moderator
The problem is the vermiculite. Heating to solution and then slow cooling 52100 results in sheeting and segregation of proeutectoid carbide. The only way to really guard against these issues and avoid embrittlement due to grain boundary carbide load up is to spheroidize anneal. This annealing is done below recrystallization and is a more thorough method of softening that will not result in carbide blocks or sheets. With a proper spheroidal anneal drilling will be as easy as it can get.

Casey Brown

Well-Known Member
Is this more of an issue with lamellar annealing of 52100 because of the significantly higher carbon content compared to most of the other forging steels?