a carbon steel blade?

[meuharris]

I got a garden knife some years (10?) ago and it was the sharpest I had ever used -like cut glass. . It was serrated and it would cut through small branches like butter (we used them for pruning young trees) The downside was it was really brittle and if you were tempted to push it instead of drawing it towards you it would snap. Would that have been a carbon steel blade? Where could I order them from (I don't seem to have much joy in googling *carbon steel blade* so maybe it is some other manufacturing method.....

[Steve Firth]

Are you sure this was a knife and not a pruning saw?

For knives, I would be surprised if you couldn't find a particular style of knife here:

I have the suspicion that what you actually had was something like this:

look like folding knives but they are saws that cut on the pull stroke. The design of the teeth gives a smooth cut and it takes very little effort to cut through even thick branches. As you say, the blades are usually high carbon steel and they are brittle and can be easily broken.

I prune several hundred trees a year and use a combination of a chainsaw and one of the Felco folding pruning saws. Felco tools are fairly standard for professional use, since they offer a good price/performance balance.

[Don]

Was it a Japanese pull saw by any chance?

[Dave Baker]

What you had was probably a pruning saw. Sharpened to cut on the pull stroke rather than the push stroke like a conventional saw has two advantages. You can use it more easily in confined spaces and when it's working the blade is in tension rather than compression so it can be harder and more brittle because it'll be less likely to bend and break. That means it can take a longer lasting edge. The disadvantage is you can't put as much down force into the cut as you can when pushing a saw.

Brittleness in steel is mainly a function of the hardness rather than the carbon content. A blade heat treated to very high hardness levels will hold an edge for longer but snap easily. A softer blade will blunt quickly but be easier to resharpen. The trick is getting the balance right. If it was plain carbon steel it would have rusted quickly after outdoor use and if it was stainless steel it wouldn't. That might tell you more about what it was made from. Spring steel, about the most elastic steel you can make is actually just a plain carbon steel heat treated and then tempered back to reduce the hardness.