Thread: Broken razors and grain structure

I remember seeing some videos of someone breaking some bigger razor names and they would snap cleanly except the last few mm near the edge which would be springy and hold together. Would have to flex it back and forth before it would break. Have any of you notice this in any of the razors that you've broke? I've been trying to find the video of it.

The ones I did all snapped because I clamped them in a vise and hit them with a hammer.
If the crack would stop near the edge, I think that would indicate that the edge is tempered significantly softer than the body.

glad to see the blade get some use!!!! very interesting , it does look clean and tight grained tc but it still makes me queasy seeing it again,, I was going to ask for it back after your done and frame it ,, might reconsider that

Originally Posted by tcrideshd

glad to see the blade get some use!!!! very interesting , it does look clean and tight grained tc but it still makes me queasy seeing it again,, I was going to ask for it back after your done and frame it ,, might reconsider that

Oh no problem. After all I only need it to make an exact replica. Once done you can get those pieces back with the new blade. It has a history with you so it is only fitting that you have the final say about what to do with them

Originally Posted by JSmith1983

I remember seeing some videos of someone breaking some bigger razor names and they would snap cleanly except the last few mm near the edge which would be springy and hold together. Would have to flex it back and forth before it would break. Have any of you notice this in any of the razors that you've broke? I've been trying to find the video of it.

Like Bruno, all mine were clamped a a vise and broke (all snapped clean).

Originally Posted by JSmith1983

I remember seeing some videos of someone breaking some bigger razor names and they would snap cleanly except the last few mm near the edge which would be springy and hold together. Would have to flex it back and forth before it would break. Have any of you notice this in any of the razors that you've broke? I've been trying to find the video of it.

Steel can be hard and flexible. The flexibility in the videos would most likely be attributed to a very thin thickness of a factory ground razor. Modulus of Elasticity does not change with hardness. Think fillet knife, feeler gauges, or a singing razor.

Just thinking out loud.

Charlie

Originally Posted by spazola

Steel can be hard and flexible. The flexibility in the videos would most likely be attributed to a very thin thickness of a factory ground razor. Modulus of Elasticity does not change with hardness. Think fillet knife, feeler gauges, or a singing razor.

Just thinking out loud.

Charlie

I agree steel can be hard and flexible.
Once brought to a breaking point can a portion break and a portion stay attached? My thought would be no unless there was some type of differential heat treating.
I've broken more then my fair share of razors I've never had a razor only partially break unless I didn't something wrong with the HT.
That being said, I could be wrong! It won't be the first or last time

There is a differential in thickness, where it is thicker it will break, where it is thinner it can bend. The heat treat can be constant and have this work.

When I mess up grinding and turn a blade into foil, the steel is hard but very flexible.

Charlie

I have seen that too. However, on any razor that is still thick enough to be a razor, a crack should propagate all the way through unless there is a hardness gradient breaking the crystalline surface.

Actually, I had a razor that I water quenched by partially dunking it in water, and then pulled out. The differential hardening was clearly visible as a hamon afterwards. I pulled out the blade and let the heat from the thick spine seep back into the blade, tempering it on the go. I saw this trick from an old sheffield knifemaker. I think he was 82 or such, and the video was from the eithies iirc. Sadly I cannot find the video anymore.

Anyway, as it was tempering, I noticed the straw blueish color crawl back to the edge. When the edge was straw, I dunked it whole. Unfortunately, there was still too much heat in the spine, and the edge had lost all flex. It cracked in 2 spots. However, the cracks both stopped at the line where straw became blue. It is now a 6/8 razor

This leads me to believe that indeed, a crack will run propagate until it stops at a hardness gradient.

Originally Posted by spazola

There is a differential in thickness, where it is thicker it will break, where it is thinner it can bend. The heat treat can be constant and have this work.

When I mess up grinding and turn a blade into foil, the steel is hard but very flexible.

Charlie

I totally agree, if ground to point of tin foil the hardness can still be there. I've done it a few times, most of the time it's thin enough for me to break the edge with my fingers.
I guess I'm just have a hard time seeing how the edge could survive the force required to break the spine. I may have a razor around that I tin foiled. If so I'll video it and see what happens.