Thread: I need advice on a crumbling edge.

A few days ago, a member send a Wade & Butcher "American Razor", for honing.
It arrived in a "dull as butterknife" state, with only a partial bevel. I have completed the bevel 3 times now. Each time I come close to completing it, the toe half of the very edge completely crumbles away. At first I thought it was caused by some corrosion at the edge. The blade is restored to a mirror finish, but there is a lot of corrosion pitting as evidence that the razor has been seriously rusted at one point in time.
I have removed the crumbles with a few careful breadknifing strokes, and started over 3 times already, spending my entire afternoon at it today.. For the 4th time, I'm once more at the verge of completing the bevel, but the first signs of disintegration are already showing again.
After further contemplation, my best hunch is that during restoration, part of the razor overheated and lost its temper?

I've asked the owner to provide me with any additional information about this razor.

I managed to shoot a picture of a chunk of the very edge, that's loosing integrity. If I perform 2 or 3 more laps, the chunk will be missing, leaving an indentation at the edge, that can be seen with the naked eye (just above the visual threshold). The entire toe half of the edge is full of those chips missing. The other half of the edge develops just fine and smoothly.

Anybody has any ideas?

From what I have read and been told, a loss of temper is not going to cause a defect like this.

what it could be perhaps and inclusion, or the result of micro cracks caused by initial quenching, or the toe may be too hard and brittle

Always happens in the exact same place or near? Does the blade taper toward the toe? Wouldn't this effectively lower the bevel angle?

One thing I have considered but have not investigated too in depth is the possibility that some razors either by flawed design or premature hone wear on the spine have bevel angle too low, which may cause micro-chipping to occur too easily. So, just like a chisel that chips in a given task- raise the bevel angle until it stops

It occurs along the entire first half, from the toe to the middle.
Upon inspection, I can see fine lines, parallel to the edge, running through the bevel. I looks as if the ruptures occur at these microcracks.
I have raised the honing angle to 6 layers of tape, without any improvement. I also expected to get rid of the problem, once I got into "fresher" steel. Not.
The blade didn't taper near the end. Actually it is a bit wider near the toe, as typical on many of these old blades. By the way, the razor is a wedge (slightly hollow). I don't have an overly wide bevel, which seems to suggest that the honing angle is not too shallow.

Bart.

Damage like that I agree looks like it is internal to the steel. The question is what caused it. If the rust was severe it could have compromised the structure of the steel. If the edge was too thin and that was causing that situation it would just micro chip but that's not the case you have there.

Bart was kind enough to not mention before contating me, but these are my razors he is dealing with. The one in question was a resto done by another member on SRP who I am currently trying to contact to find out more info about it.

Also I am glad it was not simply my terrible honing abilities that meant this razor wasnt being honed effectively. But if anyone can sort this, surely Bart and the rest of you honemeisters can.

I'll welcome any questions I can answer.

I went back and really looked at the pic Bart, The lines you are talking about I can't really make out, but I think if they are rather fine and pretty straight, that Kevin might be right and you are looking at a initial heat treating issue... If the lines are rather squiggly then I think I might be right, and this is a corrosion issue.... After you did the bread-knife strokes and reset the bevel could you see the lines more easily????

It's a beautiful restoration. And if I understand well, we should rule out the possibility of temper issues. I hope the member that did the restoration job understands that I had to ask in order to rule it out as a possibility.

Do you guys think I should raise the honing angle any further?
If so, more tape than 6 layers is going to be awkward. Maybe it would be better to attach a thin aluminum strip of under one layer of tape.
Has anyone any experience with raising the spine that high?
Other suggestions?

Thanks,
Bart.

It's acting more like corrosion damage Bart, the rust is inside the steel creating a swiss cheese effect under the nice shiny outside...

This is one reason I always post, that if you are going to restore a previously rusted edge, The first step should be to set a rough bevel "Before" doing all the clean and shine work...That way you can look at it under magnification and see what the underlying steel looks like...

I have only had a very few heat damaged blades cross my bench and they normally hone fine, out to about the 8k level, then they just will not hold that edge after one shave, but I haven't had them lose chunks like that only the swiss cheese steel from rust is what I have seen act that way....

Good points on that post Kevin....

Here’s one theory -

“The combined effects of stress and corrosion can result in a special type of failure known as Stress Corrosion Cracking (SCC). This arises under a particular set of circumstances for a given alloy: specific alloy condition plus specific corrosive media and sufficient local tensile stress. Chloride induced cracking of stainless steels, caustic cracking of plain carbon steels and ammonia damage to copper alloys are typical examples of this problem.

SCC is believed to be nucleated at pitting damage sites and develops under the action of local tensile stresses as a highly branched network of fine cracks. At each crack tip the combined action of the tensile stress and specific ions in the corrosive media cause continual crack propagation with little evidence of local deformation.

Stress corrosion cracking presents an especially difficult problem, since not only is it highly localized but it can occur in environments that are merely mildly corrosive to the material. The damaging concentration of the harmful ions in that environment may be quite small and difficult to detect and, even in the absence of applied stress, residual stresses in a structure can often be of a sufficiently high level to cause SCC and failure in service.
In a given situation the time of exposure needed to cause SCC failure depends on the stress intensity at any pre-existing or developed crack tip. The concentration of stress at the tip of a sharp crack or flaw can be quantified in terms of the Stress Intensity Factor, K1. It determines the growth rate of SCC cracks for a specific alloy environment combination. Catastrophic failure of a component will occur when this factor reaches a critical value, the Fracture toughness of the material, K1C. This enables the determination of allowable defect size in design to avoid failure under given loading conditions.”
Your fine old Wade & Butcher has likely been exposed to over 100 years of corrosive influences and in all probability the stress induced in the polishing & honing process was sufficient to begin the failure.

There is obviously no way of telling how far the micro-cracking permeates the metal or how much will have to be removed to find that perfect edge, but I wish you good luck!