Thread: Edge Restoration - Heavy Bevel setting

OK, so I agree that a deep stria from low grit anything will result in a notch on the edge (can we call this kind of notch something other than a chip, because chip, to me, means it fractured) . I'm questioning this sub surface, work hardening damage idea, where if a notch occurred, it would indeed be a chip because it would be caused by the breaking of a brittle area in the edge.

I was rewriting some of the last paragraph in my previous post while you posted so it may read differently to what you had read.

The more I think about this subject and how to test for it, the more I realize why there is no consensus on what is actually occurring.

I will have my metallurgist brother read this exchange when he is here over the weekend and see if he has any input. I'm not sure he has done much with abrasive wear though.

It is an easy problem to replicate, just set a bevel on a 325 DMT with pressure then hone it, see if it chips at the finisher.

As to why, exactly… don’t know, were all guessing. Do know the fix, though.

I think I see why I'm not having these chipping issues. I tend to be somewhat light handed and I was not really noticing all of the posts saying "pressure". Even setting a first bevel on a newly forged razor I tend to stay pretty light.

Being a knife guy for so long has been a bad thing when it comes to razor honing, dang if I don't over pressure anytime I'm not in full concentration, a couple of Old Razors end up with chipping no matter what I do, heck, they can chip out stropping too heavy on the hanging unit.
More time, more muscle memory, more solid concentration, all things I have to work on to avoid micro chipping.

I'm having fun though Lynn.

Bluesman
Is there any follow up on this topic, or on another post. You brother could maybe answer some important questions.

Alx

Originally Posted by bluesman7

The more I think about this subject and how to test for it, the more I realize why there is no consensus on what is actually occurring.

I will have my metallurgist brother read this exchange when he is here over the weekend and see if he has any input. I'm not sure he has done much with abrasive wear though.

Originally Posted by alx

Bluesman
Is there any follow up on this topic, or on another post. You brother could maybe answer some important questions.

Alx

At the time I decided that I would have a hard time describing what the mechanical properties of the situation are, since that is part of our quest. Without hands on type knowledge of honing I doubt any material science types would be able to shed any light on what is actually occurring.

Thinking about it further I think that it is safe to say that a rouge particle that can put a deep scratch in the bevel is either attached to the hone or firmly anchored by keying into the hone grit. As such the edge could hit the particle head on. In that scenario it would be easy for the pressure to be high enough to distort the steel past yield and cause brittleness due to work hardening. Earlier in the thread I could not see this occurring because I was trying to imagine the work hardening happening within the steel under the scratch and I thought that the thin edge would just deflect away relieving the pressure, but a head on hit to the edge eliminates this deflection possibility.

Hmmm. I just finished making another razor. When making a razor, setting the first bevel can take some time and I know that many makers use diamond plates 'at this point in time' figuring that there is already some damaged steel from the grinding to get past anyway. This time I did all of my bevel setting with a 1k Chosera to evaluate whether I was really saving time with coarser hones. I had much less problems with chipping and felt that there was less damaged steel to get past. In the end it likely saved time. I did make some changes to my heat treating on this razor, so that could be part of it, but for now I'm in the 'avoid coarse hones' camp.

Just posted this on another thread but it is appropriate here too.





The third picture at the site; https://jendeindustries.wordpress.co...razors-part-1/ shows some chips at the same places where gouges show further back on the bevel (IIRC these pictures are a knife edge not a razor, but for discussion it does not matter) I used to think that this type of chip was actually just an exposed groove, but it is clear that the groove is completely honed out just behind the edge. I now believe that the steel does get damaged when the edge hits the high particle straight on and then the particle goes on to cut a gouge in the bevel. In a softer hone, a rogue particle has a better chance of fracturing or simple moving out of the way and doing less impact on the edge.

Oops, missed this when it was fresh. I agree that the coarse hard particles could likely cause this type of sub-surface damage pretty easily. The key thing is to look at it as Victor described - the impact occurring in line with the apex as the edge is brought into the particle in question. This is a tiny area of impact, so it wouldn't take a whole lot to get to that 100ksi number.

It isn't probably going to occur in the other plane along the flat area of the bevel - which makes sense, as all the damage seems to occur only at the edge. The impact could be enough to fatigue that bit of steel that gets driven back to the point that it weakens and gets ripped out later after more honing and possibly flexing a bit.

Another thing to consider - using the diamond plate in the opposite direction (edge trailing rather than edge leading) might well prevent this damage, after which one could switch to edge leading for the 1k and up stones. I am quite keen to try edge trailing strokes for the whole job until the very end as well after seeing some of Todd's latest images and ideas at scienceofsharp.