10 replies to this topic

[RingingAnvil]

I have found a couple of boxes of old planer blades and due to the slight thickness and width i thought they would make a great series of fillet knives for the entire world. Does anyone know what kind of steel they might be (i put their birthday at 1958) and how to treat them? Perhaps they wouldn't make good blades at all.

[bigfootnampa]

I've no idea what steel they might be but likely one that will make blades with decent cutting qualities. You might find them a tad on the smallish side for filet knives but they should make some nice carving knives and you might get some smallish filet knives from them. They should make decent hook knives or hoof knives.

[ThomasPowers]

Planer blades are often alloys of extreme hardness and NOT FLEXIBLE.

Think about getting some *large* (as in 6" wide) bandsaw blades used for cutting trees into lumber for material that is both flexible and capable of taking a good edge.

[BIGGUNDOCTOR]

My friend's neighbor was a custom bladesmith, I believe his name was Bob Howell. He made one regular knife, and it was a fillet knife which he sold to commercial fishermen. He use Ats 34 stainless for his blades. He took one that he had finished put the tip against the table top, then pushed the handle down until the blade was forming a 90 degree vee, Very flexible, and yet quite hard with good edge holding qualities.

By planer blades I take it that you are talking about a large power planer, not block/hand planes. Most planer blades I have seen are made of High Speed Steel, and would not make a good fillet knife. It may be worth your while to find out what kind of planer that they fit, and sell them. Take that money, and buy some known alloy to make fillet knives;Ats34, 1095 spring steel, etc.

[RingingAnvil]

Thanks for the all the help and advice everyone.

[steve sells]

RingingAnvil, on 09 March 2010 - 11:42 AM, said:

Thanks for the all the help and advice everyone.

you will find even more information if you read in our blade smithing section.

[thingmaker3]

Here we go again...

"Flexible" means "thin." And that's all it means. An annealed peice of given size takes the same force as an as-quenched piece of same size when it comes to bending. Do NOT take my word for this - go out to your shop and TRY IT.

Sure, some steels have higher strength than others and will take a set (or snap off) with less force per unit cross section. But you can't "heat treat for flexibility." You have to design for it!

[reefera4m]

thingmaker3, on 17 March 2010 - 08:28 PM, said:

Here we go again...

"Flexible" means "thin." And that's all it means. An annealed peice of given size takes the same force as an as-quenched piece of same size when it comes to bending. Do NOT take my word for this - go out to your shop and TRY IT.

Sure, some steels have higher strength than others and will take a set (or snap off) with less force per unit cross section. But you can't "heat treat for flexibility." You have to design for it!

I'm trying to understand your 'you can't heat treat for flexiblility' statment. While I agree that the 'design' (as in blade geometry) is a significant factor (as is the steel you choose), I also know that heat treating can also affect flexibililty. If I were to take a leaf spring of 5160, 'flexible' in the beginning then forge and shape it to a common hunting knife shape then improperly heat treat it, it would end up either too soft and flexible (or just soft and bendable) or too hard and brittle. If I heat treat it properly the blade will have some 'flex' to it and yet be quite tough. When adding the 'edge quenching' aspect of heat treating, you harden the edge more that the spine with the intent of having an edge that will retain its sharpness while the softer spine will be more flexible and not as brittle. I consider the proper combination of annealing, normalizing, quenching and tempering to all be under the umbrella of 'heat treating'. The opposite of 'you can't heat treat for flexibility' would be you can "heat treat for brittleness'. Forget to temper and see how 'inflexible' the blade can be - just drop it on a concrete floor.

[Robert Mayo]

thingmaker3, on 17 March 2010 - 08:28 PM, said:

Here we go again...

"Flexible" means "thin." And that's all it means. An annealed peice of given size takes the same force as an as-quenched piece of same size when it comes to bending. Do NOT take my word for this - go out to your shop and TRY IT.

Sure, some steels have higher strength than others and will take a set (or snap off) with less force per unit cross section. But you can't "heat treat for flexibility." You have to design for it!

Finaly someone understands ground thin and proper heat treat makes flexible without breaking.

Thankyou Bob

[son_of_bluegrass]

reefera4m, on 29 August 2010 - 11:09 PM, said:

I'm trying to understand your 'you can't heat treat for flexiblility' statment.

I think (and I could be wrong), this a question of semantics. One way to define flexibility is simply the ability to be bent. From one stand-point, heat treating has nothing to do with flexibility so narrowly defined, the flexibility merely comes from the alloy and shape. The amount of force required to put some level of bend in the blade is the same regardless of heat treat.
A looser definition of flexibility includes the ability to return to the prior shape. This is resilience. Using this definition, heat treat does have an effect as the heat treat helps determine when the metal takes a permanent bend or breaks.

ron

[thingmaker3]

reefera4m, on 29 August 2010 - 11:09 PM, said:

If I were to take a leaf spring of 5160, 'flexible' in the beginning then forge and shape it to a common hunting knife shape then improperly heat treat it, it would end up either too soft and flexible

No, it would not. You would have the wrong elastic limit, but you would not have changed the Young's modulus. It would still take the same force to bend the knife by a given ammount prior to exceeding that elastic limit. It just takes a set more easily, which is NOT the same thing.

Don't take my word for it... TRY IT.

son_of_bluegrass, on 30 August 2010 - 02:33 PM, said:

I think (and I could be wrong), this a question of semantics.

Yes. Most knifemakers use the wrong semantics and confusion reigns supreme. I encourage everyone here to learn what these words actually mean.

son_of_bluegrass, on 30 August 2010 - 02:33 PM, said:

A looser definition of flexibility includes the ability to return to the prior shape.

A piece of steel returns to shape when we do not exceede the elastic limit. And yes, heat treatment definately changes the elastic limit of a piece of steel.

But heat treatment does NOT change the Young's modulus aka modulus of elasticity. Nor does heat-treating change the modulus of rigidity.

The modulus of rigidity, by the way, is proportional to the third power of thickness. If a knife B is 1.25x as thick as knife A, we need almost twice as much force to bend it the same ammount. That 1.95x force goes into 1.25x the area, though.



And HARDER steel has a HIGHER elastic limit. Again - don't take my word for it, go out to your shop and experiment!!!!