Thread: D2 Steel: Sharpening, belt sander - belt comparison.

I received the zirconia belts today so I was finally able to compare the belts to find out which one cut faster and whether the investment is worth it.

The belt sander:
1.5hp
150mm wide belt
running at 1725 rpm (2700FPM)

The Belts:
Pic #1 - Zirconia 60 grit 'blue' belt ($15 new, special order through Alltools)
Pic #2 - Standard 60 grit 'brown' belt (40 minutes of previous use but in very good condition). General purpose use, can normally be used to sharpen tools. (Search for Derek Cohen and belt sander for some good posts)

The D2 Steel:
Pic #3 - Part of buy #1 organised by Thumbsucker. Two identical blades were used for the comparison, neither had been ground before. Each was 50mm x 100mm x 8mm.

The Comparison:
I decided that there was no need to grind for a long period to start with. If the results were not clear after 3 minutes then I would simply repeat at 10 minutes until a result was apparent.

Although the recommendation for the zirconia belts is to use heavier pressure I used the same pressure as I used for the standard belt to make measurement simpler. Later I did try heavier pressure, see below.

Pic #4 - The timing was done using a standard kitchen timer set for 3 minutes. I stopped the timer at 1 minute intervals (i.e. twice) to cool the blade. Even though it was not necessary for the standard belt I wanted to do it that way so it would be the same as the zirconia, since I suspected that would generate more heat.

Angle - I set the table at a 45 degree angle as I hoped it would make for a clearer photo.

The standard belt.
Pic #5 - The three minutes passed uneventfully, the blade was slid across the belt in a repeated fashion using moderate pressure, stopping twice to dip in water and cool it. At the end of the three minutes I measured the bevel. You can clearly see it is 3mm.

The zirconia belt:
The first thing I noticed with this belt was the straw coloured sparks that went all the way around the belt shroud and emerged at the top coming down towards my hands. I could also detect a 'coarser' feel to the blade running across the belt. Again, the blade was slid across the belt in a repeated fashion using moderate pressure, stopping twice to dip in water and cool it, except this time I needed to stop as I could feel the heat in my fingertips, stopping again at 2 minutes because I had to (close to being too hot this time but I wanted to use the same timings). At the end of the three minutes I measured the bevel. In pics 6 & 7 you can clearly see it is twice the size of the other bevel.

The result was decisive at 3 minutes so no further comparison was attempted. I'm sure a mathematically minded member could work out how much more metal was removed but I can tell you it was more than double.

Clear Winner.
The blue zirconia belt is, by far, the fastest stock removal abrasive I have used for these D2 blades. At $15 for the belt, it will save quite a few hours establishing bevels and re-sharpening my four blades. The items below are listed in order of effectiveness for abrading D2.

1. blue zirconia belt (1)
2. standard brown belt
3. aluminium oxide grinding wheel (to hollow grind)
4. blue-max grinding wheel
5. grey grinding wheel
6. very coarse/coarse DMT diamond plate
7. fine/ultra fine DMT diamond plate (form a fine bevel and flatten the back)
8. shapton 5000 grit pro stone (hone the bevel)
9. finer shaptons to polish the bevel as desired.

I would not recommend:
King Stones - I found they simply did not cut effectively on the hard D2. I 'think' the bond is too weak. (they are great for other steels though!)
Scary sharp (wet and dry paper). The blades are simply too hard. But! I have not tried it, this is supposition.

Recommended approach to sharpening a new D2 steel block:
Ideally, for new blade that needs a complete grind, my experience to date leads me to believe the following methods to be the best approach:

• Use the blue zirconia (1) to establish the primary bevel at 25 degrees (for the same reasons given by Derek Cohen in a previous post).
• Next, the aluminium oxide grinding wheel (3) to hollow grind the bevel and make it easier to sharpen in future.
• The fine diamond plate (7) can be used to prepare the bevel for honing and to flatten the back. Note that members have already noticed the D2 steel (as supplied) needs to be "roughed-up" so the wedge can grip it. The top two thirds of the blade are sufficient for this and the diamond stones (6) or (7) will do a quick job of it.
• Finally the honing is best done with a Shapton Pro stone. I used a 5000 grit and got a mirror surface reasonably quickly. Use other Shapton higher grits if desired.

Note on Diamond Paste - I do not have any and I cannot say whether it would be an advantage over any method I have listed, however, I would imagine it would not be of any use until after the main bevel has been created. From there, only a little work is left so paste would most likely work as well as the Shaptons.

Caveat - please remember this comparison is specifically for the very hard D2 steel and the recommendations do not apply to softer steels. Furthermore, any of the other methods will work, just less efficiently (in my limited experience with D2). Use whatever you have, but if you can get hold of something with zirconia in it you should see a marked improvement.


Footnote. As mentioned at the start of the comparison, I used even pressure when grinding on both belts. Research into a specialist website found by BobL indicated you needed to use heavy pressure with zirconia to get it to cut effectively. I can vouch that THIS IS CORRECT. After the comparison I did a further grind for three minutes - see the last pic, #8. It really chewed into it, it also generated heat quickly and quenching was done in 25 second intervals.