Thread: Edge Restoration - Heavy Bevel setting

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.

I am going to stay away from diamond plates on every razor except the very worst that need a lot of metal removed for the simple reason that a rogue chunk in my fine hone put DEEP gouges in a couple of razors, just not worth it. YMMV.

Ditto that - I only use them for heavy damage repair such as chip removal or complete blade reshaping. I'll stick to my C1k or SP2k for bevel setting.

After seeing Todd's images of the DMT plate surfaces it's pretty clear where those rogue scratches are coming from. His images show quite a few rogue diamond particles that are far larger than the plates' specified grit level. Most of these are torn out during "break-in" of the plate, but some do remain.

Originally Posted by eKretz

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 going to try this on the next razor that I make. If the edge on impact is the problem, which I suspect it is, then this should eliminate the damage. Might be a while, work and taxes have priority.

For me the solution is simple, I do not fully set bevels with Diamonds even high grit diamonds,1k.

I get the bevels close but not meeting, then fully bring them together with stones, joint the edge and fully re-set the bevel with a 4k again.

Most recently I have been experimenting with a Naniwa 2k green brick, with very good results as a bevel setter with a much shallower stria. I do believe on some razors even 1k stones may be too aggressive.

Jointing and removing a bit of the edge, helps get to good, solid steel.

Victor, it would be interesting to see what happens with a new razor. But I suspect with some hard razors, Hart’s for example, much the same is happening with aggressive belts used for grinding on hard steels. CNTG made a nice razor that was very, very hard from his knife steel and very prone to chipping, much of the edge had to be removed to get to good steel that would hold an edge, this I suspect was from grinding and hard steel.

They stopped selling them, for that reason I believe, before I could buy more to test further. For Harts, jointing and lapping film work well for a chip free edge, some just have to be honed a few times to remove enough metal.

Look forward to your results.

Originally Posted by Euclid440

Victor, it would be interesting to see what happens with a new razor. But I suspect with some hard razors, Hart’s for example, much the same is happening with aggressive belts used for grinding on hard steels.

Look forward to your results.

Bruno demonstrated his edge trailing finish grinding at Charlie Lewis' razor making meet last week. Probably another good idea for avoiding edge on impact.