VIDEO: Spyderco ZDP-189 hard cutting/retention test

[unit]

As an update....

I had an illuminating discussion with a pretty smart fella' that suggested (in a round about way) that I look into the angle of the bevel a bit further. I got out the trusty precision micrometer and took some measurements of the bevel in a few places. A few calculations and sensitivity analysis later I felt pretty confident that I was a little off in my ability to hold the knife level during sharpening and my bevel angle was not exactly as I thought.

Turns out this thing is more like 11 degrees inclusive. It also shows a fairly high uniformity (very small variability in the bevel angle throughout the length of the blade). Not sure if anyone really cares (thin is thin...and perhaps most won't go this far anyway), but it does show me that ZDP is a very impressive steel.

For you number guys...the sensitivity analysis indicates that my measurements could yield angle estimates off by a half a degree either way. Regardless of the actual angle, I remain convinced that it is lower than 13 inclusive.

 

[ricklee4570]

Very impressive. I wouldnt have thought that the edge holding would be that good at such a shallow angle.

 

[unit]

Very impressive. I wouldnt have thought that the edge holding would be that good at such a shallow angle.

Well, it is and it isn't. What you saw was real...no tricks there, but the way I did those cuts did not encounter anything harder than nylon and polyester reinforced rubber (~3 different compounds of rubber...some soft some fairly hard). Point being, I never hit anything like metal or stone...if I had, you can bet that some degree of chipping or rolling would have occurred.

By taking the edge SUPER thin (it has now been thinned down even FURTHER to about 8 degrees inclusive) you get stellar cutting performance, but some chipping (if I encounter some of the harder stuff like stones and metal). The solution is to put on another steeper angle "micro" bevel that is just big enough to remove the small chips and voila! I have a bevel that the steel can better support, and a super thin blade immediately behind that (cutting) bevel.

Note "micro" is in quotes because it is a little more pronounced that a true micro bevel, but some people call it that.

 

[DennisStrickland]

ken i imagine that to get an equal angle bevel the length of the entire edge is a variable that many of us had'nt considered . i'm sure for that precision most would need good jigs. i'm still going to go the apex edge pro route. thanx for info.
dennis

 

[So-Lo]

Thanks for the update

 

[unit]

ken i imagine that to get an equal angle bevel the length of the entire edge is a variable that many of us had'nt considered . i'm sure for that precision most would need good jigs. i'm still going to go the apex edge pro route. thanx for info.
dennis

There in lies a "problem"...Jigs often tend to produce a variable angle as you trend away from the clamp attachment point on the blade. As you undoubtedly understand, the variability in the angle is consistent and reproducible (so long as you pay attention to your setup). It also is not really a "problem" if you like the results.

On a few of my blades I have intentionally used a thicker angle near the tip for edge strength in that area (especially useful for those of us who sometimes use our tips for enlarging holes and piercing).

Regardless, I think you will be quite happy with the Edge Pro...it looks like a fantastic device.

 

[unit]

Thanks for the update

You are very welcome. It looks like you have a nice review floating around regarding this knife:thumbup:

It is a nice and versatile package. It seems like the ZDP Stretch was a "sleeper" in the knife community for a long time, and now it seems to be gaining a lot more fan fair...perhaps that is just my perception. Regardless, I wish I had found it sooner!