# Metal properties of a knife with a durable edge **URL:** \ **Category:** Factual Questions\ **Tags:** tools-electric-diy\ **Created:** [July 30, 2023, 1:57am UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811 "2023-07-30T01:57:45Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [July 31, 2023, 11:57am UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/21 "2023-07-31T11:57:15Z")
> [@HoneyBadgerDC](#): > > It is a Greenlee, made in Rockford Illinois Well that should be a good one. Greenlee are a very reputable manufacturer. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [July 31, 2023, 12:22pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/22 "2023-07-31T12:22:26Z")
May be worth mentioning that as for the guy I knew (he is no longer around to ask, unfortunately) who made knives out of tool steel, they were “normal” knives, not thin blades for woodworking. There may be a general tradeoff between toughness against chipping/fracturing and edge retention, with a super durable edge obtainable by using a very hard steel. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [July 31, 2023, 12:27pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/23 "2023-07-31T12:27:44Z")
> [@Francis\_Vaughan](#): > > Well that should be a good one. Greenlee are a very reputable manufacturer. It is a very good one, I think this one might be from the late 1950’s , Another tool I have problems with is my wood rasps. They started manufacturing them in Brazil and Mexico and the quality took a dive. My favorite rasp in a Nicholson 49, less than 8 hours use and they are pretty much shot. They seemed to go downhill in the 1990’s. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [July 31, 2023, 6:32pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/24 "2023-07-31T18:32:24Z")
Here’s an article from [**toolmanblog** on older blades made from crucible steel.](https://toolmanblog.wordpress.com/2016/01/22/what-is-cast-steel/) I’m not familiar with the site. It discusses the use of crucible steel and how some tools will be marked with **WAR** , indicating a product known as **Warranted Cast Steel** which was crucible steel cast into bars. ---
**Author:** ![Steven\_Maven](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/steven_maven/32/3272_2.png) [@Steven\_Maven](https://boards.straightdope.com/u/Steven_Maven)\ **Post date:** [August 4, 2023, 2:28pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/25 "2023-08-04T14:28:10Z")
> [@HoneyBadgerDC](#): > > One time I was telling a student that I preferred a not so sharp draw knife, and I ran my finger over the edge. It was razor sharp and cut me quickly. When I was a Boy Scout in the late 1950s, they taught us that the safe way to determine the sharpness of an edge is to draw your fingertip PERPENDICULAR to the edge. Perhaps you knew that but forgot momentarily? ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [August 4, 2023, 2:31pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/26 "2023-08-04T14:31:17Z")
> [@Steven\_Maven](#): > > When I was a Boy Scout in the late 1950s, they taught us that the safe way to determine the sharpness of an edge is to draw your fingertip PERPENDICULAR to the edge. How on earth is cutting your finger a safe way to test a sharp knife? And if it doesn’t cut your finger it’s not a test for sharpness at all. ---
**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\ **Post date:** [August 4, 2023, 3:55pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/27 "2023-08-04T15:55:58Z")
I used to test my pocket knives by shaving my arm. I have less hair than i used to. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [August 4, 2023, 4:22pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/28 "2023-08-04T16:22:24Z")
That is what is usually considered a safe way to test a knife’s edge. I usually just try to cut a sheet of paper held in the air when I’m sharpening a kitchen knife so arm hair doesn’t end up on food, utensils, or countertops. ---
**Author:** ![Steven\_Maven](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/steven_maven/32/3272_2.png) [@Steven\_Maven](https://boards.straightdope.com/u/Steven_Maven)\ **Post date:** [August 4, 2023, 10:36pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/29 "2023-08-04T22:36:41Z")
> [@TriPolar](#): > > > [@Steven\_Maven](#): > > > > When I was a Boy Scout in the late 1950s, they taught us that the safe way to determine the sharpness of an edge is to draw your fingertip PERPENDICULAR to the edge. > > How on earth is cutting your finger a safe way to test a sharp knife? And if it doesn’t cut your finger it’s not a test for sharpness at all. I thought that when I used the word “safe,” it would be obvious that you WOULDN’T get cut. On one hand, apparently almost everyone else on this thread knows WAY more about knives than I do. On the other hand, I consider this tip to be part of Knives 101. I am surprised that it is unfamiliar. Does anyone else know this? Maybe my description wasn’t clear. Let me try again in much more detail, and hope that my explanation is not condescending. FIRST Hold a butter knife in your less dominant hand with the blade vertical and the edge up. Run your fingertip along the edge in the direction of the blade. Clearly, if the blade were sharp, you would have cut yourself. Now lightly pull your fingertip PERPENDICULAR to the edge of the blade. You will be able to feel how sharp the edge is (not very), but you will not get cut. NEXT Try the same motions with a carrot (or any other vegetable of your choice) on a sharp knife. The first motion will cut the veggie depending on how hard you press. The second motion will not harm the veggie. (It might shave a little off the surface, but your skin is stronger.) LAST Now you should be confident enough to try your fingertip on a sharp knife. **Obviously DO NOT run your fingertip in the direction of the blade.** Lightly pull your fingertip PERPENDICULAR to the edge. You will be able to feel how sharp the edge is, but you will not get cut. Try several more knives (depending on how many you own) to compare their relative sharpness. Is that clearer? ---
**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\ **Post date:** [August 4, 2023, 10:39pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/30 "2023-08-04T22:39:11Z")
I understood the first time. But I wouldn’t do that with a sharp knife. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [August 4, 2023, 10:43pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/31 "2023-08-04T22:43:53Z")
> [@Steven\_Maven](#): > > Lightly pull your fingertip PERPENDICULAR to the edge. Note that when you shave with a razor-sharp… razor, obviously you do not slice, but you do not hold the edge perpendicular to the skin, either— maybe at a 30-degree angle at most. Otherwise you will get cuts and nicks and scrape/irritate your skin. Also NB the sharper an edge is, the less force it takes to cut into your skin. So if it is really absurdly sharp and you run your thumb across the edge, it gets risky. E.g., would you do it with a diamond knife? ---
**Author:** ![crowmanyclouds](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crowmanyclouds/32/19884_2.png) [@crowmanyclouds](https://boards.straightdope.com/u/crowmanyclouds)\ **Post date:** [August 4, 2023, 10:44pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/32 "2023-08-04T22:44:05Z")
> [@DPRK](#): > > I met a machinist who made some knives out of D2. I’m to no end amused by the fact that not that long ago D2 was only seen in custom/semi-custom knives and today it’s dismissed as a ‘budget steel’. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [August 5, 2023, 2:13pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/33 "2023-08-05T14:13:34Z")
> [@Steven\_Maven](#): > > Is that clearer? I must apologize. I should have figured out that’s what you meant in the first place. However, while that seems to be a reasonable means of determining when a blade is dull and needs sharpening it doesn’t sound all that useful for telling when you are done sharpening. ---
**Author:** ![Steven\_Maven](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/steven_maven/32/3272_2.png) [@Steven\_Maven](https://boards.straightdope.com/u/Steven_Maven)\ **Post date:** [August 5, 2023, 5:58pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/34 "2023-08-05T17:58:14Z")
> [@TriPolar](#): > > while that seems to be a reasonable means of determining when a blade is dull and needs sharpening it doesn’t sound all that useful for telling when you are done sharpening. I will stipulate that. I started to draft another long message but I just decided not to post it. ---
**Author:** ![Steven\_Maven](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/steven_maven/32/3272_2.png) [@Steven\_Maven](https://boards.straightdope.com/u/Steven_Maven)\ **Post date:** [August 5, 2023, 6:02pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/35 "2023-08-05T18:02:09Z")
> [@DPRK](#): > > would you do it with a diamond knife? Like I said, I know very little about knives. I’ve never heard of a “diamond knife” but I would do this with anything. You just have to keep your touch VERY gentle. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [August 5, 2023, 6:25pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/36 "2023-08-05T18:25:30Z")
A diamond knife is a knife with the edge made out of diamond. Not for kitchen use, because it would be too brittle (even though the edge is hard and durable) and way too expensive, so they are for medical and scientific use. I thought of it because the edge radius is a few atoms; in fact putting any pressure on it, with your finger or otherwise, at right angles to the edge will chip and ruin it (regardless of how careful you are not to slice your finger off); it is for cutting only and not flexible like metal (think of those ceramic kitchen knives). ---
**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\ **Post date:** [August 5, 2023, 7:03pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/37 "2023-08-05T19:03:41Z")
Curiosity piqued by this thread, i tried gently running my thumb perpendicular to the blade of my kitchen ceramic knife, which is reasonably sharp, but not razor sharp. It just felt like a knife. I couldn’t tell boo about how sharp it might be. ---
**Author:** ![Steven\_Maven](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/steven_maven/32/3272_2.png) [@Steven\_Maven](https://boards.straightdope.com/u/Steven_Maven)\ **Post date:** [August 5, 2023, 7:54pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/38 "2023-08-05T19:54:42Z")
Since you didn’t say that you got cut, I’m going to assume that **didn’t** get cut. That was my only point. Thanks for the validation. (Mic drop emoji) ---
**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\ **Post date:** [August 5, 2023, 7:59pm UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/39 "2023-08-05T19:59:43Z")
It’s just a kitchen ceramic knife. It’s not as sharp as the knives i whittle with. I still wouldn’t try it with a sharp knife. Also, i didn’t press down hard enough to have any sense at all of how sharp it is. The answer is, it’s still plenty sharp for its job. The micro-serrations help with that. But i couldn’t tell that by feeling it. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [August 15, 2023, 5:11am UTC](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811/40 "2023-08-15T05:11:54Z")
I found some scalpel blades made by coating steel with zirconium nitride via physical vapor deposition. Seems even harder than the standard zirconium dioxide ceramic kitchen knives. Is there some reason why one could not make an entire knife out of it (which could be sharpened) rather than just an edge? [Previous page](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811.md?page=1) [Next page](https://boards.straightdope.com/t/metal-properties-of-a-knife-with-a-durable-edge/987811.md?page=3)