which tool steel

And where were you when I had logged the ## of that "knife steel" on IRC ???

Alas, its probly too late now...

I missed telling everyone a MAJOR point. Its magnetic and will rust, but very slowly. I have some old shears that sat in a shed for years with slight rusting. (I watch Ebay for limb lopper and buy them all)The shears in daily use show no rusting.

Of these candidates, do any rust but slowly?

stainless 440C H13 D2

Karl

Yes, it rusts when not full hard. Is magnetic

I don't know

Yes, it rusts slowly

There is a 440A and 440B also. I wouldn't use any 440 for this, not very tough, breaks easy. There is a 420 that may work. Used for plastic extrusion dies.

D2 is abrasion resistant would would not file well, even fairly soft. Other than that, it is a good steel for this application with an RC around 55

Don't forget 455 stainless, it come up to about 55 Rc

Beege

Karl, Steels in general rust less when heat treated, and the higher they are to their maximum hardness the less they rust.

I still think 4140 is the best choice for your job. 440 SST, H13, and D2 if hardened to anywhere near their max will be difficult to sharpen with a file as you stated in your original post. I doubt that the original manufacture used something as "exotic" as the above mentioned steels.

Also most of the loper blades that I have seen looked to be forged, which gives them very different properties than a blade made from bar stock.

Good point. A forged blade or wrench will perform unlike anything machined from stock due to the grain structure from the material flow.

With that said, some shapes (like a lawn mower blade) do not require forging to obtain the advantages of grain direction because they can be cut and formed so the grain of the steel flows along the length of the part. The rolling process for the raw material does the same thing as forging (for that shape). The cutting edge of the shear may be the same way, so long as you respect the grain direction of the material you start with.

Years ago while I was in college, I worked as a hack machinist for a manufacturing company in Raleigh. A linkage in a hydraulic assembly in a tube bender failed due to metal fatigue. I replaced it with a piece of unhardened tool steel. O1 probably. It was a very pretty piece and I was so proud to make this pretty part and get production going on that tube bender again. I expected it to be way stronger than the cold rolled steel part it replaced.

I was very surprised when it failed in less than one shift. I had the grain directing off by 90 deg. And tool steel is not very tough. I made another shaft out of some ugly old hot rolled steel and to my knowledge it is working to this day.

Grain direction man.

...

I learn something everyday on this NG. I knew wood had grain, didn't know that about steel. The original is forged, can't duplicate that. The outline shape will be laser cut out of bar stock, I'll be sure and have the length of the part line up for maximum strength. My son is having this done as a government job where he works. He asked me to provide the stock. I'll try three of the best candidates for a trial.

Thanks for all the help.

Karl

for a

I worked quiet a while at a place that made rotary cutting and creasing machines. They used 4140ht for the knives. Heat treated and ground. At one time we made some prototypes from material called "Ferrotic". It was new technology at the time. The knives worked great but the company did a great deal of business on replacement parts so they priced them where no one would buy them and then discontinued production due to low demand. I believe it is a pressed powdered carbide and something else product. You had to heat treat the stuff wrapped in foil packed in charcoal. It was interesting. this is the stuff:

apples

ye, I meant quite

Perhaps you should consider sending your orchards overseas instead of dealing with all the hassle of making new blades :)

Im thinking S7. Do a google and you will see it would work perfect.

Hi Karl,

If you come up with a version suitable for manual use with handles I would be interested in a set. Just the shear and hook, I can make up handles of some sort.

A good heavy duty hand lopper is hard to come by now days. Most of them have weak parts and take very little abuse, err hard use...

Keep me in mind if your parts aren't too expensive.