Choice of steel and heat treatment is directly related to the durability of the knife. My goal is your survival.  Many knives  are  brittle
as the steel must be hardened in order to hold an edge.  Breakage is possible  with the application of lateral force. Tempering removes some of the
brittleness, but the softer the steel the less edge holding ability. Modern CPM steels
negate the need for ultra hardness somewhat, but the brittle factor remains.
Steel Chart

ZONE tempering is stock on every Relentless knife. It is a process that has been perfected  by Japanese Samurai sword makers and used for thousands of years.  It is time consuming and difficult, but the end result is a knife with great break resistance as well as edge holding ability.

Zone tempering is NOT as seen on some production or semi production knives that can for sure absorb lots of lateral force, but trade this for
wear resistance  i.e. edge retention.
The steel used is spring steel, or (previously
spring steel i.e. 1095). or on very low quality knives stainless steel with high cromium and low carbon content.
So you get a durable knife in one aspect
but not the other. You'll spend more time sharpening which wears away your knife.

Further, it's NOT what is often seen on knives with a soft spine and hard edge with acid etched to bring out the temper lines.
That is often termed differentual tempering
and done by many bladesmiths to make the knife more durable, and good looking
as the tempering lines usually show a nice pattern etc. The spine on top of the blade is soft with the edge harder for edge retention.
Certainly this is good, and for sure gives you a sturdier knife.
OK, but we want more.
There is no beauty to it, until you need to pry open a door or window with your knife.
Then do a lot of cutting.
This process is no big secret, just a lot of extra work.
Many knife makers not willing to take the  time or expense condesendingly  call it a crowbar with an edge, claiming that knives are made to cut , nothing more.
Well I can not dispute their claim.....I just  hate to waste, so why not get the most possible use from the tool.
That is what you get from a Relentless knife.
A  process  that imparts a spring temper in the center of the knife running from pommel to tip.
This process gives you a knife that resists both bending and breaking at the application of lateral force on the knife. The steel I use is selected to enhance this process giving you a knife that is not totally unbreakable, but very nearly so with good to excellent edge holding. The spine of the knife is not soft, having the same hardness as the edge. It is also not brittle due to the use of rugged steels designed to endure.

Steel Chart Explained

Wear resistance
=edge holding ability

=resistance to strong lateral force
without deformation or breakage.
I use the steels with the
relentless logo on the chart.
CPM 3V  Super High performance Semi stainless
steel.  Super performance with strength far exceeding
all of the rest.  More expensive due to its difficulty to work with, but an investment that will be with you for a lifetime.  With properly prepared 3V steel you get a
knife that will endure extreme conditions with ease.
Easy to sharpen and keep sharp.

CPM S35V  High performance stainless steel is an improved s30V formula that offers you a better finish with more strength and ability to resist lateral force.  It sharpens easily compared to s30V steel with no edge chipping like s30V.  It resists rust and corrosion better than most stainless steels, although more
expensive.  It is the best choice for a stainless extreme
use knife available today.
8670M/L6  Extremely rugged High Carbon  Alloy steel. It has better  edge holding than 1095 with twice the toughness.
This is an L6 steel variant .
Hard to get but well worth it
if you cannot or will not afford the CPM steels.

  2017 and beyond CPM s30V and 5160 available only by request as the other steels perform better.

What about RUST and Stain

Yes rust and stain can be a problem, even on stainless steel.
Remember STAINLESS = stain- less. It stains less than non stainless but can still rust and stain if not maintained.

Interestingly the best way to STOP
rust on your knife is to use it a lot.
Since knives do their work via abraision, rust has little chance to form. It's like continually rubbing it with fine sandpaper depending on what your cutting.
Rust can and will dull your knife as the reason it is sharp is because at the edge there is a very fine feather of steel that stands up when the knife is sharp.
So keep the edge coated with a thin film of P.B. Blaster or any good
This repels the moisture in the air that would otherwise dull even stainless steel knives.


Myself and Lt Col Humphrey have done  rust tests on the steels used in Relentless Knives.
My choice for the BEST steel, CPM 3V did for sure survive 30 days submurgence in sea salt water.
The result shown in the photos below.
The knife was easily still useable and quickly brought back to new again. No oil was used to protect the knife.

Our tests were done before s35V was available.
CPM s30V rusted 2 days after a sea salt water bath.  It was
left it unattended and not dried or rinsed with fresh water.
rusts easily if not maintained or put to the hard and heavy use for which it is intended.  It can benefit from KG Gun Kote, Dura Coat, Gun bluing, or Parkerizing.


When failure is not an option, equipment that won't fail is your only option.
Incorporating the most durable steels,
exotic heat treatment and Trademarked Tri a symetrical grind gives you extreme
break resistance, exceptional edge retention,
and a strong sharp point
resulting in unequaled functional reliability.

Copyright 2016 by Daniel M. Certo Additionally, no material from this site may be copied, reproduced, republished, uploaded, posted, transmitted, resold, or distributed in any way without Daniel M. Certo's written permission. All rights reserves, and all Copyright,Trade mark and Patent laws strictly enforced