Testing Some Cheap Kitchen Knives

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me2

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I bought a RADA Cutlery Santoku a few weeks ago and have been using it for cutting vegies and such on a plastic cutting board. It would occasionally stick on the board on cutting, but only with tough cuts that required a bit of pressure, and even then, just enough to notice. For anyone not familiar w/ RADA, the knives are some form of stainless, mirror polished and about 1/32" at the spine, with a very thin edge. A 6" knife cost me $7 a the local flea market.

So, I decide to see how much of an edge it will hold on cardboard. I resharpened the knife with an 800 grit waterstone at 12 degrees to form a burr, and then used the 15 degree slots on the Sharpmaker with Medium flats of the rods. This produced a very sharp edge, capable of making strips of a plasting grocery bag. Much to my surprise, after only 10 cuts, the blade would not cut the bag.

As a check, I resharpened a Kroger house brand steak knife to the same profile using the same stones. This knife also came out very sharp, easily cutting the bag, but not as cleanly as the RADA. It took nearly 30 cuts to dull it to the point that it would not cut the bag any more.

I have compared the Kroger to my 805 TSEK in 440C from Benchmade, when both were finished fresh off the leather belt of the Harbor Freight belt sander. It came in at about 60% of the 440C, but I dont know for sure how close the blade angles were, as I just use the flat of the blade as a guide when using the sander, meaning I tilt the blade back (increase the angle) until I can barely see the flat of the blade, and then use this as the sharpening angle. It falls between 15 and 20 degrees, as edges off the sander can be touched up on the 20 degree sharpmaker slots, but not so much on the 15 degree ones, unless I take great care to use a very shallow angle.

Just to be clear, both blades were still quite sharp and easily usable in the kitchen. Both would still shave hair, even when the plastic bag could not be cut. There was a noticable roll on the RADA blade, and the Kroger blade as well. There may have been a slight burr left, but I used Jeff Clarks method of deburring with the Sharpmaker, which involves taking 30 degree per side strokes into the stone to remove any burr, then taking a few more to freshen up the edge.

Since I didnt use hardly any cardboard, I plan to repeat the tests tomorrow night using the Sharpmaker White stone fine finish, and then again at a 17/20 degree per side profile.

Every kitchen I've been in around where I grew up had several of this brand of knife. I'm quite surprised at the results, and suspect I need to repeat the test at the current angle/grit, but use a more extensive deburring step, to eliminate that possibility.

I would hazzard a guess at the hardness of the RADA blade at about 50-53 HRc. I just finished a 1095 Kiridashi that outlasted both knives by a factor of 10 and 5 for the RADA and Kroger respectively. The sharpening angels for the kiridashi are probably vastly different, as all the grinding and sharpening on it has been done free hand, including the finish sharpening using the Sharpmaker white stones.

For future reference in this thread, I rarely use the corners of the Sharpmaker rods anymore. They tend to cause more burrs than I've used them to remove, just due to the small contact area pushing the edge around a little. I say that just so from this point on, in this test, only the flats will be used for sharpening when putting on the final 15 or 20 degree bevel from the Sharpmaker.

Any more detailed info on either of these knives, and the RADA brand in general would be appreciated.
 
The Rada knives are made from T420 stainless, which I think falls a little between 420-J2 and 420-HC. I ran a sharpening experiment years ago where I totally flattened the edge of a Rada paring knife on a hone and restored it using only a V-rod sharpener. It took me 22 minutes to do the job (long for my expectation). My experience with Radas makes me think that they are much harder than you would think. I would guess that they are in the 56 to 58 range. They don't have much in the way of alloyed carbides so they should wear faster than 440A, but they may work better than you would expect.

http://www.radacutlery.com/FAQs.asp

http://www.bladeforums.com/forums/showthread.php?t=120186

Try completely removing the edge and start over. Sometimes the factory sharpening process leaves weak material at the edge that you need to strip off. Maybe your knife is softer than the ones that I have tried. The ones that I have sharpened feel funny when I hone them on a coarse hone. It just feel like a hard steel. It also takes longer to remove material than on a soft steel.

Please keep me posted on your experience. There is that concept that Cliff Stamp has been promoting that some of the simple stainless steels might work better than expected if they are heat treated to be harder than normal. This might show unexpected things possible with the 420-series alloys.
 
I plan to remove the edge from the RADA knife with the stone. I think the Kroger will have to go to the sander. It was sharpened last on the sander about a month ago, but picked up several dings in the edge that I may not have gotten out. Also, I plan to deburr by cutting straight into the stone before moving to the sharpmaker, then deburring there as well. I was quite surprised by the Kroger, as it took over 150 cuts to stop cutting the bag off the leather on the belt sander. I already reprofiled the RADA the night after I bought it, but it would probably still benefit from a couple of cuts into the edge to remove any issues.

That is a surprising hardness for these knives. I tested one a couple of years ago and compared it to a blade I'd made from a cheap hacksaw blade. It out cut the hacksaw consistently, and I was very surprised, as I rehardened the home made blade and tempered it very low. Of course, that saw blade may have been just case hardened, because it would just barely cut annealed O1, and was a joke on Home Depot steel at 3/16. I ended up drilling holes and cutting the HD steel with a dremel. I tested them by cutting aluminum cans until they wouldnt shave anymore. My Old Timer peanut made over 100 cuts and would still shave after the same test, but both of these were about 30 to 50 or so. Anyway, its Monday and I can test knives and watch wrestling at the same time. No, really, I can. And yes, I still watch wrestling.

"Please keep me posted on your experience. There is that concept that Cliff Stamp has been promoting that some of the simple stainless steels might work better than expected if they are heat treated to be harder than normal. This might show unexpected things possible with the 420-series alloys. "

Many years ago, I repaired the broken tip on a BM balisong. I spent years trying to figure out the steel used, because it cut easily with a file, yet sharpened quickly and got sharper than my Buck. I later guessed it was 12C27. I am eager to try some of the Kershaw knives in 13C26 at the higher hardness of around 60.
 
Ok, round 2 is done with these 2 kitchen knives, the Kroger and the RADA. Both were resharpened, burrs removed by cutting into the stone, then going to the Sharpmaker medium rods in the 15 degree slots. The Kroger was reground on a 120 grit belt, followed by deburring and then Sharpmaker. The RADA was done on the 800 grit waterstone, then the burr removed by cutting 90 degrees into the stone. This was repeated before the cutting began. Both would cut curls from the plastic bags before the cutting began. The results are about the same as before, relatively speaking.

The RADA knive took about 15-20 cuts to stop cutting the bag, the Kroger took about 50-60. Both went up, which shows a good sharpening can help remove worn metal and leave a longer lasting edge.

Next, I'd like to see what a larger angle does, somewhere about 17 degrees for burr raising, then the 20 degree slots on the Sharpmaker.
 
This is a nice test. It is good to see that starting with a fresh edge does make a difference. I have been doing it routinely for so many decades that I start to lose confidence in how I reached my original conclusions. It would help if you could add a couple more well known kitchen knives into the comparison. Would you have something like a Victorinox, Wusthof, or Henckles around?
 
Sadly, no. I have been eyeing the damascus-ish blades sold at Bed, Bath and Beyond, but havent shelled out the cash yet. I have some Faberware knives that could be used, but they are the best kitchen knives I have. I was also eyeing the Henkels santoku at the local Target, but it's about 6 times the price of the RADA. I'll check the angle on my 8" Faberware chef's knife and maybe add it to the mix, most likely for the higher angle tests.

I will say one thing. You can sharpen these knives and test them in the same hour. There is none of this 500 cut business before the knife gets sufficiently dull. It would be interesting to see what the thread cutting load is when the bag stops being cut, just to quantify it for easier comparison.
 
I make the rounds of local thrift stores, Salvation Army, Goodwill, ARC etc, and pick up dull knives. You might find some good knives that way. I could probably send you some (I have hundreds). Click on my name and see if you can send me an email.
 
I forgot, I have an Old Hickory 6" boning knife that would fit in nicely. I just need a handle for it, maybe. I'll try later, maybe tonight, and see if I can cut without a handle.
 
Ok, I tested the Old Hickory a few minutes ago. I want to repeat the test after I get done regrinding the edge, but so far it looks like its slightly ahead of the RADA Cutlery knife, 30-40 cuts before failing to slice the bag. I sharpened it with an 80 grit belt, then the Sharpmaker. It was very sharp, easily slicing the bag, but possibly not as sharp as the others were initially. The 15 degree slots on the Sharpmaker left a pretty wide scratch pattern, so the edge may not have had all the course grit marks removed. I deburred the edge twice, so I dont think that was an issue. Anyway, I have some reprofiling to do before I get reliable results. There is just too much metal to take off using the 800 grit waterstone, so I'll be moving to a 120 belt then the Sharpmaker, the same as the Kroger knife. Just a reminder, even when the blades will not cut the plastic bag anymore, they will still shave using a slice and considerable pressure. I realize this tests only the short term sharpness, but once a knife gets to the point that it will barely shave, I touch it up on the Sharpmaker or fine India stone, so short term is really what I'm looking for anyway.

Edited to add: the edge on this knife was very worn, as it had been used to cut fireproofing from structural steel for a few years before I got it. Its possible that this was a factor for the relatively low cutting duration.
 
One of the reasons that I suggested finding other knives for comparison is that I suspect that your Kroeger knife is actually made of a pretty decent steel. A well processed 440A alloy blade does better at abrasion resistance than your typical 420 series. I have often found cheap Japanese no-name knives that were very tough to sharpen or dull.
 
I'll keep that in mind for the Kroger.

I just finished another test of the Old Hickory. It almost doubled the performance. I reground the edge on the sander and then sharpened on the Sharpmaker at the 15 degree slots again. This time I used the same 120x belt as on the Kroger. I suppose for the sake of thoroughness, I should resharpen the O.H. using the waterstone and retest. Sometime this week, I hope to try the Faberware chef's knife. It depends on if it needs reprofiling to reach the 12/15 degree edge I've been using.
 
Me2, a quick dumb question - is this a test with the grocery bag on a cutting board, or something else (suspended etc)?
 
Nick Hyle said:
Me2, a quick dumb question - is this a test with the grocery bag on a cutting board, or something else (suspended etc)?
Click to expand...

I just hold the bag and slice from the handle I'm holding toward the bottom of the opposite side. The really sharp ones will just keep cutting until a piece falls off. Its subjective, and the bags all have to be from the same store, but it is quicker and more consistent from person to person than shaving arm hair, which gives sporadic results for me. I tried switching from Ingles bags to Wal Mart when I ran out, and knives that wouldnt start a cut in the Ingles bags easily cut the Wal Mart ones.
 
Well, I found the downside to the 15 degree bevels on what I consider to be weaker steel. The RADA Santoku that started the thread has a nick in the blade from, as far as I know, contact with the cutting board, a polymer board. From what I saw, the nick is from a deep rolling of the edge, not chipping. Its about 1/3 or 1/4 of the actual edge bevel.

I suspect that the blunting of these knives, and many other kitchen knives has a great deal more to do with contact with the board than the food. I touched up the RADA on the sharpmaker and then cut a bananna on the board. The blade wouldnt shave afterward in the area used for cutting.
 
I agree that cutting boards are harder on blades than most meats, fruits, and veggies. How hard is your polymer board?
 
Have no idea. Its the only polymer cutting board I've ever used. My previous ones were wood of some persuasion. The RADA knife will snag and make thin cuts into the surface, so it must have hit a corner, or maybe it happened while it was drying in the dish drain. I'm usually very careful about hitting it with anything else while it dries, but that may be the cause as well. Maybe this weekend I'll test the increased edge on the Old Hickory. I upped the bevel to 17/20 on the sharpmaker. The primary bevel was too thick to cut down on the 800 grit waterstone, and using the sander polished it half way up the blade. It was originally a fireproofing knife from work anyway, so the higher bevel angle should help with durability when it goes back to work.
 
Ok, after a month or more, I've rebeveled the Faberware Chef's knife and will test it tomorrow on more of the same box used for the other tests. I have my doubts about this one, but we'll see. The thing took 3 deburring sequences on the Sharpmaker at 60 degrees included, and a boat load of strokes to remove the burr and leave a fine slicing edge off the medium stone flats. The rebeveling was done with an 80 grit belt, new this time, so only about 4 passes total were needed to reduce the bevel to somewhere near 12 degrees, so the 15 degree Sharpmaker slots leave a barely visible microbevel along the edge. I really like this knife, as it has more heft than the RADA Santoku. My only complaint is the lack of sufficient finger clearance above the cutting board, no doubt due to many sharpenings since we got it 6 years ago.
 
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