Thread: Grit issues, does any one else see a problem here

Originally Posted by eKretz

Aside from that, it's very difficult if not impossible to tell how an edge will shave (comfort/smoothness wise) from scope photos.

I'm not religious but that gets an amen! from me.

Originally Posted by eKretz

The OP still has some questions to answer before we can reliably diagnose his problem actually - like what was the exact progression on each of the photo sets? Did he take photos of his 8k work then go straight to the 16k and then immediately take photos again? Are the photos of the exact same area of the blade? How many strokes were done on the 16k? Also, how old was the 325 grit diamond plate? It is conceivable that he could have a plate that has shed a few diamond bits if it's new, as well as there being the possibility that if the resultant lapped surface on the stone could have been ragged enough that the stone shed some abrasive as slurry.

I will try to answer your questions, to the best of my ability.

First, just to reiterate, these are photos of a knife edge not a razor, just to make sure there is no confusion for any readers

The stone progression I do is 500,1k, 2k, 4k, 8k, 16k

the photos are two sections of the same side of the knife (a 7-8" fillet knife). The entire knife was honed to the 16k level. Then I marked half of the blade and honed the tip half on the 8k. The fillet had a slight bow in it curving very slightly to the left when the edge is pointed downward. Because of this I used the side that produced the best stone contact for the pics. As stated before even though I don't have pics of it the 8k I put on the knife before honing the entire edge on the 16k was comparable to the final 8k photos.

The photos again are two different spots, but I put in two photos of each spot just in case one was better than the other.

as for stroks on the 16k. I really don't know. For this I did not keep a log even though I'm hind sight it would have helped. I would say, and I know this was a lot, somewhere around 40 strokes on each the 8k and 16k. My goal was to show what the 8k was doing compared to the 16k.

My DMT is about 1 month old. But before it ever touched a stone I hit it hard with a large screw driver. And before this I had probably lapped flat my stones a total of 40 times plus also have used it to set bevels on about a dozen or so other knives

Before re honing on the 16k I lapped it flat with very light final pressure in hope thati would get a better finish.

As as a final note, since the beginning of this thread I have realized I must have been using too much pressure. Though I thought I was going light, I think I was still too heavy handed.

So I hope this answers some of your questions.

The diamond plate is a possible factor if it's only a month old. Have you lapped any very hard stones with it? Arks? Those will break in a diamond plate right quick. If you feel like you were using too much pressure it's possible you were dislodging abrasive particles from the binder and getting what amounts to a slurry...which is not good for finish. However it's odd that it isn't happening with the 8k also; unless you used less pressure with it than with the 16k.

Originally Posted by eKretz

The diamond plate is a possible factor if it's only a month old. Have you lapped any very hard stones with it? Arks? Those will break in a diamond plate right quick. If you feel like you were using too much pressure it's possible you were dislodging abrasive particles from the binder and getting what amounts to a slurry...which is not good for finish. However it's odd that it isn't happening with the 8k also; unless you used less pressure with it than with the 16k.

For lapping, I have only lapped all my Shapton GS hones and my Norton 4/8. The hardest hone it has touched was my C12k (PHID). So other than bevel setting several knives, then that's it.

Originally Posted by rlmnshvstr8

For lapping, I have only lapped all my Shapton GS hones and my Norton 4/8. The hardest hone it has touched was my C12k (PHID). So other than bevel setting several knives, then that's it.

It should be fine or you would see evidence of bad scratches on your stones.

Heres an example of what tiny high points a ml or so wide do to a King 1200

Agree, too much pressure appears to be the problem.
Scratch patterns are just patterns, it's how the edge looks that counts.
Never got too hung up on the science of the scratch, if it shaves comfortably it's right.
If the shaves uncomfortable and you can guarantee the bevel was fully set start at the top of your progression with a few very light laps, if still not there keep moving down shave testing as you go.
Also think different blades will contribute to differences in scratch patterns.
Interesting discussion but for me too much detail and analysis. I used to over complicate the science of honing, myopicaly looking at scratch patterns through a loupe but gave up and just checked the edge. I'm now very relaxed and chilled out!!

Come on now. The scratch pattern affects the edge. This is simple trigonometry. Doubly so as there are two bevels meeting at the apex. Just think about it - if you have a scratch of x depth on both bevels on a razor with a 17° bevel that coincide with each other at the apex, you're looking at a dip in the bevel of around 16*x. A scratch on a single bevel and you're looking at 8*x recession into the edge.

There's no need to obsess over scratch patterns, merely try to minimize scratch depth. The man asked us to analyze his problem, and again, this is not a razor, it's a knife. There's no shaving going on here.

Originally Posted by eKretz

Come on now. The scratch pattern affects the edge. This is simple trigonometry. Doubly so as there are two bevels meeting at the apex. Just think about it - if you have a scratch of x depth on both bevels on a razor with a 17° bevel that coincide with each other at the apex, you're looking at a dip in the bevel of around 16*x. A scratch on a single bevel and you're looking at 8*x recession into the edge.

There's no need to obsess over scratch patterns, merely try to minimize scratch depth. The man asked us to analyze his problem, and again, this is not a razor, it's a knife. There's no shaving going on here.

Ok agree on that point and bow to superior knowledge, geometry was never my strong point! Thinking about this some more as I've just been hand sanding a blade, I totally see your point as if the scratches aren't smoothed out I'd never get the metal smooth enough to get that mirror shine on the blade. Maybe I'll pay more attention to the edge patterns when I next hone a razor from bevel to finisher then compare the edge to another razor where I've not been as fussy. You see that's what I love about this site you're always learning and it makes you think. Thanks

I've been PM'ed by a member who was doing the math, and just wanted to add that the numbers above were done with quick mental arithmetic - I have since rechecked and the actual difference is 3.5*x for a single scratch of depth "x," 7*x for double coincident scratches of depth "x." Quick working sketch below with a theoretical example showing scratch depth of .001" for the sake of easy comparison. (I made a boo-boo here in my original mental calculation, the 7*x is for the double scratch as it's calculated to centerline).