Opinions wanted on 4340 steel

[LRB]

Is it even worthy of consideration as a knife steel?

 

[deker]

Is it even worthy of consideration as a knife steel?

For things that need to be tough more than sharp sure. Throwing knives and throwing axes come to mind. In big stock it's also good for hammer making and power hammer dies.

-d

 

[mete]

Agreed . Hammers and 'hawks .Like 4140 only tougher .

 

[scottickes]

4340 is commonly used to make Case Carburized tapered roller bearings from. The ring is machined to a bearing shape, then it is place into a carbon rich furnace and soaked to allow carbon to penetrate the outer layers. Making it somewhat like the structure of an M&M candy. Hard shell on the outside, soft tough inner core. This allows a bearing made this way to be very tough and resist cracking all the way through.

This is why it would make a great throwing knife as stated above, since it would be very tough. The edge would not get hard enough to remain sharp in even the lightest of most knife cutting duties.

Before anyone asks, it would be extremely difficult to get the atmosphere in small furnaces to produce enough carbon from the burning, excess propane to create a hard outer shell without compromising the atmosphere with excess oxygen. The furnaces used to case carburize bearings are very sophisticated and expensive.

I'm a bearing representative and couldn't imagine pulling it off in my home shop.

 

[mete]

Since when does Timken use 4340 ?? When I was there we made it from 4620, 4320,3310 .Carburizing grades are usually no more than .20% carbon !!

 

[scottickes]

We've been using some steels in the .4 percent range for a while. You made me look it up to make sure that my memory was accurate. The .4 percent carbon in the core, allows for a bearing that is less likely to flex under heavy loads, but still able to handle shock loading without cracking through.