Tempering problem?

kelbro · 07-11-2008, 04:47 PM

Thought I would post this here as well as the honing forum because I'm pretty sure that it's not a honing issue...

I have an old Sheffield quarter-hollow blade that has been giving me fits. Setting the bevel was not a problem. Honing on the lower grits yields a shaving edge, just a little 'gritty'. It feels great on the TPT. The problem seems to occur when I get to the higher grits or try to strop it with either a pasted paddle or the linen/leather, the edge simply goes away. It will not pass HHT and will only make about 1/2 of a shave before it becomes useless.I have seen this situation before in sharpening knives and was usually able to attribute it to cheap steel but this is not a cheap blade. Is it possible that this blade is just not tempered very well? I have put great edges on a lot of razors but this one has me pulling my hair out, literally

Thanks for any suggestions.

Mike Blue · 07-11-2008, 05:34 PM

It doesn't sound like a problem with the blade being hard enough because you would have noticed it abrading more during honing. Maybe a wire edge/angle issue?

kelbro · 07-11-2008, 07:22 PM

Quote:

Originally Posted by Mike Blue

It doesn't sound like a problem with the blade being hard enough because you would have noticed it abrading more during honing. Maybe a wire edge/angle issue?

It does hone quickly. Maybe a little too quick. That is what prompted my concern. It hones quick and then loses it quick. Leaves a little more swarf on the stones than some razors too. I thought that I might be rolling the edge on the strops but it looks good under magnification (15x and 150x). Puzzling when it's just one razor that exhibits this symptom.

JoshEarl · 07-11-2008, 07:28 PM

I have made a couple of blades that were quite soft but still shaved well and held an edge just fine. Mike tested one for me, and it came back at 52-54 Rockwell C. A typical Sheffield blade might be 59, and a Solingen blade might be 60.

So I don't think that's your problem. Unless the blade looks like it's been through a fire or something... Did it have any multi-colored tarnish on it?

If I were you, I'd spend some more time working it on a fairly coarse hone in the 1-4K range. The type of thing you're describing usually happens to me when the edge isn't quite set properly. The bevels aren't meeting completely, so you're getting a wire edge that seems sharp and then instantly crumbles. Quarter-hollows and wedges will require a surprising amount of work to get them shaving the first time.

That's my theory.

Josh

kelbro · 07-12-2008, 04:05 AM

Well, same thing tonight so I thought that I would try something that I read on this site. Taping the spine. I have used this idea of a secondary bevel on working knives and it seems to work there. It makes touchups a breeze for several honings until you have to reset the primary bevel. The edge on this razor got up and stayed up through my fine hones and 50 laps on the strop. I'll try shaving with it in the morning and see how it holds up.Thanks for the suggestions.

randydance062449 · 07-12-2008, 04:48 PM

I agree with Josh. It sounds like the bevel is not yet developed. The test results are a "false positive". The old wedges take a lot of work on the bevels. Sorry!

smythe · 07-12-2008, 05:37 PM

That blade could be a “lemon”, tempering could be bad, geometry could be off…
If you use a layer or two of tape and the edge improve then shave with it a few times to see how long the edge lasts. If it does not improve… the steel may have been badly tempered (or somehow lost it at some point in its life).

Another suggestion is to take your self out of the equation… send it out to another honemieter, I am sure someone out there would love to help resolve this mystery.

CS

Mike Blue · 07-12-2008, 07:12 PM

Sadly, there is a phenomena called decarburization that can occur when the blade is being brought up to heat treatment temperature and allowed to soak too long in too hot a fire, like at the end of a batch of blades. Sometimes that layer of steel needs to be sharpened away before getting down to the hard steel underneath. I like all the other suggestions too.

kelbro · 07-12-2008, 08:13 PM

As an update, I shaved with it this morning and it did pretty well. Held up the entire shave and still passed HHT after my normal 10 lap post-shave stropping. It could be the extra thickness but it sort of points to a bevel-setting problem. I am pretty sure that I had good bevels both times before but who knows? If the edge lasts, I may return to the un-taped process, re-set the bevel, and see if it will hold up. Interesting problem. I have restored quite a few razors and never had one this challenging. Live and learn!

Mike_ratliff · 07-13-2008, 01:15 AM

You would be amazed at the things you will find when honing different razors.
I've honed several hundred razors, and I'm still learning and discovering new things. Lynn's honed probably several thousand blades, if not tens of thousands of blades, and I'm sure he still gets an occasional surprise.

JoshEarl · 07-13-2008, 01:53 PM

Definitely points to a bevel issue, as you've noted. I have a couple of wedges that have edges that look great but pulled like crazy, even after several hours of fiddling. In the end, I was able to get them shaving nicely by using a pasted hanging strop. The pasted hangers can be a good way to bludgeon uncooperative edges into submission in a hurry.

Josh