Metal Core in Razors... True?

I was visiting with an old friend yesterday who knows nothing about straight razors, but has a good background in knives and such. I buy a lot of straight razors, and mentioned the fact that I have run into multiple occurences of a very odd type crack in blades. I was referring to the vertical crack in the tips of straight razors that typically extends about 1/2 to 3/4 inch into the blade. These cracks don't affect the cutting edge, since they occur about half way up the blade toward the spine.

He said something similar happens in axes, and surmised it is due to inserting a hardened core into a softer metal outer section. Something like this, he said, is done during manufacturing...

• Split the center of an ax blade in a V shape
• Insert into the V very hard, tempered steel
• Heat to white heat to fuse the metals together

That creates an ax of hard metal in the middle at the cutting edge, having softer metal for most of the rest of the ax head. He said you can't visually detect that there is a difference between the two type (temper types) metals. But, that occasionally, the ax head will split where the metals were incorrectly or incompletely fused.

My friend surmised that the same thing might be done with straight razors. And, it made sense. And, it would explain the frequent, but to me odd split in the tips of some razors.

Has anyone heard of this insertion of a core of harder temper steel into straight razors?

As an add on comment, if true, it would mean that the spine would be softer than the edge. (I have honed quite a few razors, and haven't noticed. This is probably because I am very careful in how I hold the razor while honing to keep as much pressure as possible off the spine, using the spine only for establishing honing angle and not for resting during the honing pass.)

Layering steel seems like a waste of time on a razor
IIRC layering with a softer outer shell is to give the blade some toughness to withstand impact
It could possibly be done with an old forged blade to save the good steel for edges, but doubt it would be possible on a 1/2 or more hollow

If it occur on the toe of a full hollow its more likely that the lack of shoulder on the toe end has resulted in a stress fracture

It's not generally done in mass produced razors, but you can get some customs such as the Takeda blades made by Mastro Livi. These have blades made from steel by Shosui Takeda, which is layered hard inner / softer outer similar to Japanese sword blades.

They are great shavers, but IMO layering is unnecessary in razor blades. You don't need it to withstand the treatment an old sword would get, hacking off heads etc.

Another consideration is that the honing angle will change over time, and get shallower and shallower as the spine wears more than the cutting edge.

It is virtually never done. If it is done at all, it is for aesthetic / novelty reasons. And you'll know it because you'll have paid for it. :)

San Mai Damascus has an SG1 core and steel of different composition surrounding it. It is not often used in straights due to its higher cost than carbon steel. I can not see the advantage of procuring such higher costs to use a core in a straight razor when they are primarily functional, and it is the edge that is critical. An Axe and a straight are designed and intended for entirely different functions.

If you consider an axe its primary use is to chop. Perhaps to reinforce it a stronger core would prevent the edge from folding. This is only a possible suggestion, I know very little about axes other than their function.

Now consider a straight razor. Its purpose is to cut hair as close to the skin as possible. It requires an extremely sharp edge which it is granted by the heat treatment of, and the properties of, the steel composition itself. It does not require a swinging force that an axe does in order to fulfil its purpose, rather very light pressure in addition to its own weight.

Other than the aesthetics that Takeda Damascus exhibits, which could be positive or negative depending upon one's own view; I can not see how a differently composed core would make any difference to or improve a straight razor, or improve it significantly or noticeably than quality carbon steel.

Of course not being a steel or razor smith I could be wrong and indeed my views ignorant and if so I would enjoy reading what is true about different cores in straight razors, if at all anything.

To add a little different thought, the grinds are not the same. An axe is a heavy convex grind where the side slabs would be a very heavy backing to the edge on either side. The (sometimes) heavy hollow grinding would remove all that extra support material on a razor and leave mostly only the good steel in the center. I think that would defeat the intended purpose.

It works for a larger blade where the more expensive good steel is not as readily available and you want it to go farther in the product. It would have been more a practical economy than anything. A smallish razor would not benefit as much since so much of the less expensive material would be removed by grinding.

Otherwise the technical skill and aesthetics would be better reasons for doing a complicated billet for such small blade.

Would it be possible to post pictures of a couple of these blades? In my experience, a vertical crack on a razor usually starts at the edge and extends upward toward the spine. There is a common area of corrosion, however, that resembles a crack but is not, and fits all your description except the "vertical" part. Many razors which are stored damp develop a line of corrosion which starts at the toe of the razor below the spine, and runs horizontally, longitudinally along the blade for about a half inch at the most. It looks like a short black line and feels rough. When sanded and polished, it turns out to just be pitting, not a crack at all. Sometimes the line is on both sides of the blade, sometimes on only one. I have personally never seen a razor that had a vertical crack in the blade that did not start at the edge. I have not seen a vintage razor that showed any type of metal core, either. Just my .02 cents worth!

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Originally Posted by Croaker

Would it be possible to post pictures of a couple of these blades? In my experience, a vertical crack on a razor usually starts at the edge and extends upward toward the spine. There is a common area of corrosion, however, that resembles a crack but is not, and fits all your description except the "vertical" part. Many razors which are stored damp develop a line of corrosion which starts at the toe of the razor below the spine, and runs horizontally, longitudinally along the blade for about a half inch at the most. It looks like a short black line and feels rough. When sanded and polished, it turns out to just be pitting, not a crack at all. Sometimes the line is on both sides of the blade, sometimes on only one. I have personally never seen a razor that had a vertical crack in the blade that did not start at the edge. I have not seen a vintage razor that showed any type of metal core, either. Just my .02 cents worth!

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+1... the scale/wedge line,, this line usually corresponds with the spot where the blade can touch the scale and the water that was trapped in the wedge-scale space gets on the blade...I see this a lot, but vertical is much much more rare and like Croaker said "usually starts at the edge"...

Just a quick note regarding that axe construction.

That is reminiscent of the construction of samurai swords where an extremely strong core of high-carbon steel which serves as the edge metal is surrounded by (and hammer welded to) a softer core which serves as the body of the sword.

The metal on the edge (which is tempered to higher level of hardness) takes an extremely keen cutting edge, but is brittle. The softer metal which forms the rest of the blade is softer and 'cushions' the shock when the sword is used. The two steels sandwiched together allow for superiour qualities compared to a blade made of either steel alone.

The same technique is employed in the axe construction. Again, this would be with an eye towards allowing the axe to have an extremely hard metal to take a long-lasting, sharp cutting edge which is then supported by the body of the axe made of a softer grade of steel which allows the axe head to absorb shock without shattering.

Straight razors are not intended for, nor subjected to, these sudden striking forces. To that end, sandwich construction is normally not required. Instead, the blade is one piece of forged steel which is then hardened to suit the requirements of the cutting edge.

Hullo, I found this particular crack in my new Dovo just yesterday.

A couple of people have been commenting on rust along the spine of new Dovo's so I got mine out for a look. To the naked eye I found 3 rust spots in a line down the centre of the tip. Under 20x on my loupe, there is indeed a crack from the spine, extending pretty much the depth of the wedge section of the tip. This crack runs almost the full length of the spine, with corrosion starting in several spots.

Being a straights newbie, I've been trying to ascertain if this would be classed as a manufacturing fault, or just something I'm stuck with. I guess an email to the UK wouldnt hurt?

I recently saw a wedge razor with a clearly visible core when viewed end on and my guess would be that it would be similar to some knives with a high carbon core and low carbon shell,when the blade is hardened and tempered the low carbon shell is hard enough to resist excessive wear but soft enough to wear easily at the edge exposing the hard core making sharpening easier,i have seen more japanese chef knives made like this than other styles/makes and some are done for costs because of the steel used for the core,some even have a stainless shell to comply with sanitation requirements,there are so many variations on this sort of practise that it's really hard to know exactly what they use and how it's tempered

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Originally Posted by Picaro

Hullo, I found this particular crack in my new Dovo just yesterday.

A couple of people have been commenting on rust along the spine of new Dovo's so I got mine out for a look. To the naked eye I found 3 rust spots in a line down the centre of the tip. Under 20x on my loupe, there is indeed a crack from the spine, extending pretty much the depth of the wedge section of the tip. This crack runs almost the full length of the spine, with corrosion starting in several spots.

Being a straights newbie, I've been trying to ascertain if this would be classed as a manufacturing fault, or just something I'm stuck with. I guess an email to the UK wouldnt hurt?

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Dovo razors are stamped or drop forged if you prefer the term. Its possibly a section that was not cleaned up fully in the grinding stage.

Hey Picaro, could you post a picture of what is going on with your blade?

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Originally Posted by onimaru55

Dovo razors are stamped or drop forged if you prefer the term. Its possibly a section that was not cleaned up fully in the grinding stage.

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Drop forging will leave a line where the flashing occurs between the two halves of the forging dies. This is a good choice for possible explanations. But I would have thought that the finishing process would remove most of that.

The other test would be to etch the blade in some cider vinegar. Any differences in the two steels, if welded that way, will be readily apparent.

The only other factor, especially in a monosteel, would be heat treatment stresses. These are small blades and making steel hard is a violent process. Without pictures, this discussion stalls a little.

This is my first attempt at magnified photo's so I hope this is ok.

Yep, that looks like a crack.

Looks symmetrical enough to be from the drop forge rather than a crack but pics can lie.

The rust coming out of it makes me think it is a crack, and that water has wicked into the crack and caused the rust.
I'd start getting happy about sending it back.

It certainly looks like a crack from two metals not fusing together properly. However I would say, due to lack of distortion between the two sides as well as the location of the crack, the two metals fused together were of the same composite.
I don't know how the blade was forged however my observations would support the suggestion that it was caused because of a drop forging process.