Author Topic: Was it the PA-70 John D. Verhoeven tested?  (Read 1711 times)

Offline Sharpco

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Was it the PA-70 John D. Verhoeven tested?
« on: October 14, 2017, 02:07:32 pm »
http://www.bushcraftuk.com/downloads/pdf/knifeshexps.pdf

Does the Chrome oxide compound on page 27 mean the PA-70?

Offline cbwx34

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Re: Was it the PA-70 John D. Verhoeven tested?
« Reply #1 on: October 14, 2017, 03:30:36 pm »
http://www.bushcraftuk.com/downloads/pdf/knifeshexps.pdf

Does the Chrome oxide compound on page 27 mean the PA-70?

It doesn't look like it, if you read these two quotes...

Quote
This was followed by experiments done on leather strops coated with a thin layer of honing compound. The compound used here is called Micro Fine Honing Compound supplied in the form of a wax impregnated bar having a deep green color. The abrasive contained in the wax bar is a 0.5 micron size chromium oxide.  Unless other wise stated this was the honing compound used on the subsequent experiments described here.  p.19

and

Quote
The experiments of the previous sections demonstrated the advantages of using chrome oxide polishing compound with leather strops. Hence the leather polishing wheel of the Tormek machine was only used after charging with the chrome oxide compound. The procedure for charging was to coat the leather with mineral oil, apply the wax stick to the rotating wheel to produce a non-uniform heavy layer on the leather and then smooth this layer to a thin thickness with a knife edge on the rotating wheel.  p.25

I'm glad you posted this... I've read it before, but reading it after spending some time on this forum, sheds new light on it. 
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Offline Ken S

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Re: Was it the PA-70 John D. Verhoeven tested?
« Reply #2 on: October 14, 2017, 03:50:08 pm »
Interesting post and reply. Like CB, I have seen this study before. It deserves more careful and thorough reading. (I saved it to ibooks.)

I think of chromium oxide compound as green colored sticks. They are a staple in the honing arsenal. Given the thoroughness of the report, I expect the author would have specified Tormek PA-70 Honing Compound if he had used it. I may be wrong, however, I recall the abrasive in the Tormek compound is aluminum oxide. It is initially more coarse and breaks down to a much finer grit with use. It may not be as exotic as some of the newest diamond compounds, however, it has performed trooper service for decades and continues to do so. So much of sharpening, honing, and polishing is a balancing act between fast cutting and leaving a smooth surface. In my opinion, PA-70 favors leaving a smooth surface. It cuts reasonably fast and leaves a nicely polished surface.

Ken

Offline Ken S

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Re: Was it the PA-70 John D. Verhoeven tested?
« Reply #3 on: October 14, 2017, 04:55:30 pm »
A thorough reading of the report will require more time than I have available now. Based on a quick reading:

I do not recall any mention of the stone grader. As much as we might like to proceed directly from the 220 grit SG wheel to the leather honing wheel, proper sharpening requires the middle step. The middle step diminishes the scratches to enable the leather honing wheel to polish the edge. Tormek has always been up front about the three step process.

I can understand the desire for consistency in the test, however, the part of the test using the Tormek should have followed Tormek's recommended procedure, including using PA-70 honing compound. I do not doubt the good intentions to produce an honest evaluation. This test reminds me of the tests comparing fifteen film developers the photo magazines used to run periodically. The tests were fair and uniform. However, the expert doing the tests invariably used only one or two developers for his own work. With either film developing or sharpening, I would expect a skilled, experienced operator to have more nuanced skill with his preferred methods. I would expert this expert to be reasonably skilled with all the choices. Whether it is film developing or sharpening, I would prefer each method to be tested by an expert in that particular method using a combination if the recommended factory technique and his personal preferences developed over years of use.

I will study the test more thoroughly as time permits.

Ken

Offline wootz

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Re: Was it the PA-70 John D. Verhoeven tested?
« Reply #4 on: October 16, 2017, 02:38:42 pm »
Tormek Honing Compound grit is 6000-8000, particles 3 to 1 micron - vs Chrome Oxide 0.5 micron