Sharpness testing

[grepper]

I was a bit reticent to post this as it has been discussed here before, and at this point I'm more than fashionably late in joining the party, but the Cliff Stamp stuff got me interested enough in edge retention that I needed some way to measure edge sharpness.  So, finally, I ponied up and bought an Edge On Up sharpness tester.  I had delayed because at my age I'm trying to shed rather than collect stuff, and I thought I'd test a few edges, get a feeling for what it meant, and it would become yet another closet dust collector.

I had suffered the same misgivings about getting a microscope, but now I use it all the time.  I am finding the same to be true of the sharpness tester.  In just a few short days, it has joined the microscope as simply part of my regular sharpening routine.

One aspect I hadn't really appreciated was how informative the thing is in experimenting with what does and does not work in various sharpening procedures.  Things like how more or less pressure when honing affects the sharpness.  Did additional honing increase or decrease sharpness?  And this can vary from blade to blade, with different edge angles, steel types and amount of burr present.

I'm finding its accuracy and repeatability good enough to provide real, useful information, especially in conjunction with a microscope.  A sharpness tester does not provide visual edge assessment, and a microscope does not test sharpness, but together they provide a pretty broad picture of what is happening down there at the cutting edge that isn't readily apparent without instrumentation.   Cool tools.

Anyway, I thought it was interesting enough that, even though I'm late to the party, I'd chime in too.   

[Ken S]

Being able to repeatably quantify sharpness is a giant step forward. Two recent test results come to mind:
1) With my test chisels, the 80 grit CBN wheel alone yielded a BESS reading of 500. Using the same chisel and wheel, but grinding away from the edge produced a BESS reading of 400.

2) These chisels, going directly from the 80 grit wheel to the leather honing wheel with Tormek honing compound gave a BESS reading of 130. This was remarkable, but not as sharp as the traditional Tormek three step method with the SG-250. This yielded a BESS reading of 90-100.

Much more to learn.

Ken

[grepper]

I suspect that was simply showing that there was a big old, nasty, gnarly burr and your most excellent honing procedure removed it.

Edge inspection without even looking at it.

[Ken S]

I suspect that was simply showing that there was a big old, nasty, gnarly burr and your most excellent honing procedure removed it.

Grepper, the 80 grit produces the most excellent "big, old, nasty, gnarly burrs", and does so quickly. Quickly is the key word, especially since those burrs were part of a major reshaping (bowl shape back to spindle shape). For day to day work, I still feel more comfortable with a finer, slower stone and more genteel burrs. I confess that it is nice to have such fire power availablewhen needed.

Ken

[RichColvin]

I have great respect for Ken, & he has been referencing his Edge On Up for ages.  He is a great resource for product testing :   Our own version of Consumer Reports. 

I've just not seen how it would be used to make me a better sharpener.  Alas, Grepper has enlightened me.

So, I'm interested in which model of Edge On Up tester that you bought

[grepper]

I purchased the PT50B, which is the next iteration of the PT50.  It's not widely available yet, but just shoot Edge On Up an email and order directly from them.  Here's a hint- You might as well get an extra spool of test media while you're at it.  EOU is in the process of redoing their web site to reflect new stock, and it should be live very soon.

Here's one example of how it's useful.  I wanted to regrind the bevel on a knife to a more acute angle, and it needed sharpening anyhow.  I knew it was sitting at about 225g BESS.  So I ground away with a coarse grind, gave it a light hone and tested it.  It had the same reading. 

How could that be?  Under a light, it looked like I had completely set the new angle.  I knew that I must not have ground completely to the edge, but just for grins and to test my gut feeling I threw it under the microscope.  Sure enough, there was still a micro bevel from the old edge angle. 

So after a little more grinding and a light hone I tested again; 140 this time, which was about where I wanted to be for that knife.  Yes, it could be sharper, but 140 really is pretty sharp, and I generally don't want to turn my kitchen knives into a DE razor blade.

It does not take long to get a good feeling for about how sharp your general method of sharpening gets a blade.  If a test shows it's out of spec, then you know something's up. Maybe there is some micro burr left, or the blade still needs more grinding, etc.

As well as learning by experimenting with different methods, and how consistent you are in getting the entire edge sharp, etc., it also helps with QC/consistency of the final edge.  Once a blade is pretty sharp, it's, well, pretty sharp.  Without test equipment, that's about all you can say about it... It seems pretty sharp and call it good.  But with the tester you can quantify it with an actual number.

One thing about the Tormek is repeatability and consistency.  A sharpness tester provides the same to the level of sharpness you are producing.  A cool tool to add to your arsenal I think, and it's fun.

[Ken S]

I really like using BESS because it gives a known, repeatable number to edge sharpness at a reasonable cost. I can make sharpness readings in Ohio, USA, and share them with members throughout the world. This is more dependable than cutting paper.

It allow me to compare two sharpening methods. Identical tests may not produce identical readings, however, the readings will be close enough for close comparison.

I second Grepper's recommendation of the PT-50. I have used three models. The PT-50 is more accurate than the smaller unit, and more convenient to use than the KN-100 model.

Ken