Tempering makes your knife slightly less hard but tougher and more durable. Without tempering, your blade is much more likely to crack and therefore become useless. There are rare cases where tempering a knife is not required.
I know a guy who started making knives without even know that tempering exists. You may guess how his knives ended only after the first use. So, after explaining to him the importance of tempering a blade after quenching, his knives suddenly became durable and finally useful. This is why you should always take enough time to learn and inform yourself before you start anything, including knifemaking.
It is not so uncommon for a beginner to get confused about the parts of heat treating and many other terms used in knife making. In short, hardening involves heating the steel to non-magnetic temperature and then rapidly quenched in oil or water. As its name suggests, the goal is to increase the hardness of the steel. On the other side, tempering is the process of heating the steel below the critical temperature, usually in the oven.
Its primary goal is to reduce the hardness in exchange for increased strength and durability. To fully understand this, it is good to know what is going on during temper. After that, you let the blade cool down to room temperature. Keep in mind that your blade is still useless as it is too brittle. One drop on the floor and it is done. The goal here is to make the martensite stable and allow the austenite to finish. Now, by heating up the blade to about the martensitic start temperature and keeping it for enough time, martensite loses its brittleness.
This typically happens due to the changes in the grain boundaries. At this temperature, the austenite is much more active so it slowly finishes its conversion to martensite good. Set time and temperature play a crucial role in this process. The blade is then cooled down to room temperature. The steel now consists of tempered martensite which is good, and untampered martensite which is not good.
This is why we need to do another tempering cycle to finish the conversion of leftover austenite. The amount of tempering needed mainly depends on the intended usage of the material. Install the app. Welcome back! Did you know you can mentor other members here at H-M? JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser. Thread starter ecdez Start date Aug 21, Welp, I had my first crack at making a forming tool from O-1 tool steel.
Here's what I did. First try. Do a little more research for the second try. Second try. Heat steel to I think Test with a magnet and it's not at all attracted to the magnet according to the internet this is an indication it's ready Quench in oil Check with file and it slides right off, yea! I can tell it's harder, but the file still digs in I got the temperatures right off the sleeve the steel came in from Travers.
I'm using clean motor oil last resort I know, but it's what I have on hand I did use the same piece for the second try which might have been a bad idea but I figured if it didn't work the first time then it's not hardened and can be tried again. Anyway, I was hoping someone here might have some experience and can point out my obvious flaw in my process.
Thanks in advance! Joined Feb 1, Messages 6, Click to expand Thanks for the response. I used separate ovens for the two different processes. I did not do a file test on the first try between the two processes. One the second attempt I may not have been as thorough in my filing process as I should have. Mueller Manufacturing Company [10]. Because O1 became a very popular tool steel, it is relatively difficult to determine who used it in knives first.
It has been popular with both forging bladesmiths and stock removal knifemakers due to its wide availability in a range of sizes, and ease in forging and heat treating. One knifemaker known for his use of O1 was W. I contacted Randall Made Knives and they confirmed to me that their understanding is that the steel used did not change. An article on Randall knives by Jim Williamson identifies the steel as being produced by Uddeholm [14].
Uddeholm sold a version of O1 under the name UHB at that time [15]. So while it is hard to say that Randall was the first to use O1 he was an influential user of it in the very early period of American-made custom knives.
I am not sure why he used Uddeholm steel. Perhaps it was available in a better size, cost, or he felt the steel was higher quality. Below I have a micrograph of O1 that I took. You can compare it against other knife steels by reading this article. The carbides are relatively small and well distributed.
Fine carbides generally mean good toughness and edge stability. A cold treatment can be added after the quench for a small increase in hardness as well as a corresponding decrease in toughness not tested here. Despite the fine carbide structure of O1, its toughness is not particularly high when compared with other steels.
For example, A2 is probably the closest counterpart to O1 in terms of use in die steels but is air hardening instead of oil hardening. However, A2 has both better toughness and wear resistance than O1, despite the fine carbide structure of O1. The relatively poor toughness of O1 seems to be a consistent finding whether in toughness testing of Knife Steel Nerds, Crucible, or Carpenter.
Here is a comparison between Knife Steel Nerds and Crucible toughness numbers showing that they correlate very well and that the results for O1 are also similar note the scales are different due to different sample geometries :. O1 is not known for high wear resistance, it has significantly lower abrasion resistance than D2, for example [17].
And generic ratings from steel manufacturers typically show O1 having lower wear resistance than the majority of their other die steels. O1 was tested at a very high hardness 64 Rc but its edge retention was clearly lower than the other steels:. This is easy to understand through knowledge of the effects of carbides on edge retention which you can read about here. Low alloy steels in general , , O1, W2, etc.
The biggest benefit of O1 over the years has been its availability nearly everywhere and relatively low cost. It is also relatively easy to heat treat due to its austenitizing requriements being similar to other low alloy steels with the benefit of being easy to quench for full hardness, even with slow oil because of its high hardenability.
The downside is it is more difficult to anneal due to its high hardenability. Learn about annealing here: Part 1 and Part 2. O1 is also easy to finish and sharpen because of its low wear resistance. The forgeability of O1 is also very good. Halcomb Steel was purchased by Crucible only a few years later but continued to sell the steel as Halcomb Ketos for many years, and Crucible continues to sell O1 as Ketos steel.
Oil hardening steel was very popular with tool and die companies due to the very small amount of warping, distortion, and size changes the steel would see due to oil hardening. The other major tool steel companies made their own oil hardening steels which were all versions of O1 and O2.
O1 has a fine microstructure of cementite. Its edge retention is relatively low due to the small amount of soft iron carbides cementite. O1 has been common in knives for decades. Famously O1 has been used by Randall Knives starting in or so and continuing to today. Cambridge University Press, Steel Treat 21 : Steel Treat 9 :
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