The paramount effect of bond type on finished surface roughness

[Mr.Wizard]

As the creator of an abrasives reference chart I clearly state "The chart does not and cannot quantify or compare absolute performance." When I get questions like "which is finer" I try to point out that many factors affect how coarse or fine a particular abrasive behaves.

Nevertheless when I came across the graph below while browsing abrasives catalogs I was surprised by the magnitude of the effect of just one of these factors: bond type. Of course this is not a universal graph and it cannot be applied as a general correction factor; rather it illustrates just how much variability in performance there can be even with the same abrasive grain.

D Diemaker Have you had a surface roughness analysis performed on the finishes produced by your Matrix stones?

From Asahi Diamond, Diamond and CBN wheels catalog:

 

[Diemaker]

No, the most analysis that has been done is with my microscope. One other very large variable is how Matrix stones perform depending on how well and how recently they were dressed.

By the way your Diamond and CBN wheels catalog: link comes up blank, which is strange because when I hover over it I see what looks like the right address in the lower left corner of my monitor.

 

[Mr.Wizard]

D Diemaker the link is to a PDF file; perhaps your browser or network is blocking it?

 

[Diemaker]

I recently loaded Win10 from 7 and since then my browser doesn't open pdfs, it downloads them without opening them. I just found a few copies in my download folder. Time to look at my settings.

 

[Gritomatic]

I'm confused by Ry values. How comes 250-micron stone (60 grit) creates 4-microns groves maximum?

 

[bucketstove]

I'm confused by Ry values. How comes 250-micron stone (60 grit) creates 4-microns groves maximum?

Thats blue line for resin stone,
resin is probably masking the grits
its filling the gaps

 

[Mr.Wizard]

Gritomatic That's really surprising isn't it? This is the most extreme example I recall seeing claimed. I suppose if only the tips of the grains are exposed and the resin doesn't erode faster than the grains themselves this is possible.

 

[Diemaker]

Think of the context in which the abrasive is used. A powered wheel over a precision table with a controlled feed rate designed to make the smallest scratches with said abrasive. Totally different than sharpening a knife by hand. The metal bond wheel will grind smoother surfaces the longer they work since the proud abrasives will get worn down evening out the surface of the wheel. Resin bond is smoothed out when it is dressed.

 

[FortyTwoBlades]

That's a major factor in how synthetic razor hones were made. They had fairly large grit by most folks' modern standards, but they used a special surface finishing process to get it so the abrasive grains only just barely protruded above the shellac bond. It's why they often had the instructions to NOT resurface them. I liken it to setting the depth of the iron on a hand plane.

 

[eKretz]

Yeah Diemaker is absolutely correct. You can not compare a grinding machine's finishes to what you will get by hand. A grinding machine runs the wheel at very high surface speed (this alone improves finish significantly) and can just barely skim the surface, along with making repeated passes over the same area. That's how it can make a very fine finish even with what seems like a coarse grit.

 

[Mr.Wizard]

I am aware of the averaging effect of a powered wheel but that applies to all wheel types in the graph so it cannot explain the performance gulf between the metal-bond and resin-bond. Like I wrote "many factors" and this is just one of them.

 

[DeadboxHero]

The important take away here is bonding type and hardness makes a huge difference.

 

[DaveDM]

Why does the relative surface finsish between electroplated and metal bond change for diamond vs CBN. The other two bonds maintain relative performace.

 

[FortyTwoBlades]

Why does the relative surface finsish between electroplated and metal bond change for diamond vs CBN. The other two bonds maintain relative performace.

If you're talking about the two graphs shown in the .pdf you'll notice that one shows the medium being ground is ceramic and the other is hardened steel. My guess is you're seeing the difference in the suitability of the bond type for a hard/rigid/friable type of material vs. one that is comparatively soft and flexible (despite being "hard" by most common standards.)

 

[DeadboxHero]

That graph is not to be used verbatim for our purposes sharpening knife steels on sharpening stones.

It should just be used as a reminder that there are differences to surface finish between the bond type not just the grit size.

It can be a very curious thing to some folks when a stone that has a larger abrasive grain size has a finer finish than a stone that has a smaller abrasive grain size.
The bond and bond type is a big clue why.

Why does the relative surface finsish between electroplated and metal bond change for diamond vs CBN. The other two bonds maintain relative performace.