Pruner blade steel question for Cliff, Joe and all steel experts

M

mark0

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Nov 26, 2002
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I have a question regarding steel for an often used tool.

I have a variety of knives, machetes and axes and while i find that there are indeed large differences in steels, I do not get enough field usage cutting, such that it really matters.

On the other hand I need to use a hand garden pruner very often.
This is the case with many people I believe, as well as the wine and fruit growers.
Some of these folks make thousands of cuts a day.

Now I have looked around and purchased the best pruners available: I have a Felco, Bahco Pradines, Fiskars, Corona.

While some of these are superb ergonomically they have terrible steel blades (best to worst as listed).

Even for my garden usage I have blade edges rolling and chipping (not so much dulling per say).
So it is quite surprising that there is not an aftermaket for custom pruner blades, especially for professionals.
I have been to garden centers, and have seen a bunch of "professional" pruners used by staff in absolutely terrible shape.

I resharpen my pruners before usage to form a nice micro-bevel,and this helps, but even so the steels are poor.

For a pruner, the blade does not suffer any impact but it is I believe subjected to serious bending forces at the tip (on dry wood especially).
Generally pruner blades are angled one side only, like a chisel.


So I am thinking of removing the blade from my Felco and Bahco pruners, finding a custom knifemaker and getting new blades made from an ultra hard, wear resistant steel.


What do you think this steel should be.


I have read previous forums and are aware of the "best" ones used for knives, but I think that something really hard RC 62 - 65 would be good for a pruner blade.

A CPM10V, M4, D2 or even a stainless BG42 perhaps?

I have a book called Tool Steels by Roberts and they discuss a steel class
called F (F1, F2, F3), Tunsten finishing steels.

They are used at extreme hardness ~ 64C
and still have good toughness.
They also have outstanding wear resistance. The downside is that F class is not good for hot hardness and therefore it has been totally supplanted by high speed steels.

This book gives relative toughness and wear properties.
F2 is rated as a 6 for toughness (same as an L6) and 8/9 for wear (same as M4).

They say the cost for this steel is very low but the avilability is poor.

Has anyone heard of F class and is it used at all for knives?

Getting back to my pruner blades, any suggestions would be welcome as well as any thougths on custom knifemakers that would be willing to make a few blades for me.


:) :)
 
You are seeing a problem not with wear resistance but with ductility mainly due to lack of strength. It sounds like the blades are simply too soft and/or the QC is overall poor. I have used a couple of cheap pruners with no problems, but *very* infrequently.

The solution would be to go to any decent custom maker, and have them make a set of blades out of any steel they are comfortable with, and is cheap. The difference between those blades and the ones you describe will be night and day.

For specifics, something simple, 1095, or a slightly alloyed version and get it close to full hard. This will leave the edge very strong and very resistant to denting or bending. This is how the Japanese make all their bladeware, the edges are 62-65 HRC. In fact you should be able to find japanese pruners with such blades.

Moving beyond this level of steel, into something like CPM-10V for wear resistance would only be necessary if the wood you were cutting was very abrasive, and not a lot of it is of that nature. A stainless steel blade is not needed on wood, but might be on "juicy" vegetation. I can't see that damaging a blade however as it is usually soft.

BG-42 and S90V at two nice stainless steels for such use as they can both get to 63-64 HRC, and have very high wear resistance on top of that, S90V more so, but is much more expensive to work.

The first thing I would try however is a simple carbon steel, hardened very well. These will be very cheap as the steel is not expensive, and easy to work. You might even have the maker try to reharden the existing blades on the pruner.


The only thing that I would be concerned about is any possible twisting of the edge during the cutting. However with a quality pruner, I don't see that as significant. Any micro-chipping would also be eliminated with a suitable micro-bevel.

The only maker I know of that has brought up F series steels for knifemaker is Alvin Johnson, mainly due to the very fine grain.

-Cliff
 
I believe that VG-10 is used for pruning tools in Japan. There are still available some plain edge Spyderco Merlins, a hawkbill suitable for pruning in VG-10. However, the plain edge has been discontinued so they won't be around long.
 
I'd agree with Cliff.I think the pruners are just cheap steels. A well heat treated 1095 or O1 would be fine ( my agrussell kukri is 1095 and it holds up to "pruning" very well).I have an old Camillus. pruner but haven't used it enough to know how well it holds up .If you want to go stainless try D2 or 154cm. No need to go to anything fancier. The "Tool Steels" book is my major tool steel reference, every metallurgist should have one. It shouldn't be difficult to find a knife maker who would make one.
 
Camillus still makes a pruner, ask them about the steel and hardness.
 
You have nothing to lose by attempting to harden the existing blades yourself first. Get an acetylene torch (or borrow a friends), harden to nonmagnetic, quench in oil, and test for hardness with a file. if they hardened then temper in your kitchen oven at around 350 degrees for an hour and this should make them less prone to brittleness.

The worst that could probably happen is that they don't harden because they don't have enough carbon in them. In that case then pursue the custom made route. If you have good quality carbon steel pruner blades I would bet that you will get more hardness and save some money in the process. In any event it would be fun to experiment.
 
Thank you for the replies. I will give hardening one of the existing blades a try, before getting a custom one.

On my second point; has anyone heard or used steels classed as "tungsten finishing steels" F1, F2 for knifes?
 
You are likely to have warpage problems if you try and reharden the blades. If your pruners use a shearing action they may fit and cut properly if warped. If they work like some of the rose clippers where there is one sharp blade and a flat copper bar that the cutter impacts at a right angle. Those might work even if somewhat warped.
 
MarkO, now that I read your post a second and more carefull time. You should differentiate between pruning knife( Camillus still makes folders) and pruning shears and with shears do you prefer scissor type or blade and anvil type. For durable shears I would look into commercial brands.
 
The steel in the cutting blade (i.e. non-anvil) of Felco pruners seems fairly soft. This, combined with the fact that the primary bevel on the blade needs to be ground relatively acute in order to reduce binding, can produce a fragile edge.

The solution I found is simply to add a small secondary edge bevel, just as you might on a knife. I recently used my Felco #6 pruners to do quite a bit of cutting on some heavy bushes, as well as maple and other trees that were overhanging the roof of my house, and the blade held up extremely well. Many of the branches cut were 3/4"-7/8" diameter -- near the limit of what can be cut with this Felco model. The pruners performed very well and remained quite sharp, with no chipping or discernible blunting.

FWIW you can easily add a small secondary bevel to the blade with a fine India file or ceramic rod. You might want to try this first and see if it's satisfactory for your purposes; nothing to lose, except a few minutes of your time.
 
Indeed, I should have specified that it is pruning shears that I am talking about.

I will have to try hardening on a pair of the cheap ones; I can see that warpage could be a problem.

I have created secondary micro-bevels on all my pruners; this has helped but not enough I feel.
It is interesting that you have also found the blade on Felco's to be soft. Felco is considered tops in the commercial market, and has the best steel of all the pruners that I have tried.
I am looking to find some japanese ones with VG10 steel, but here in Canada, I have not found any so far.

The cutting issue is not so much with clean green wood, but with dried wood, as well as green wood that has dirt (i.e. sand particles) on it. This really gets the blades.

I know that the wine industry and fruit industry,(in California and other places), does a lot of hand pruning and training; these guys must do thousands of cuts a day. This is why I thought that there must be a custom aftermaket for replacement pruner blades; it does not seem to exist though.
I had a garden pro come to plant a larger tree in our yard and asked him about his pruners. They were Felco's, the blade was about a month old and in terrible shape, (dulled, edge bits missing).
He told me he has to replace the blades often. Felco makes replacement blades and at about ~ $ 15- 20 a pop I can see why they are not using better steel.

A pruner blade is small, it does not have a lot of steel, so even high quality should not be that expensive??

This prompted my original question; I think that shear pruner blades could do with a super hard, abrasion resistant steel (dirt and hard dried knots are the problem I believe).


The dirt problem is also experienced by hunters skinning dirt encrusted hides, but maybe not as evident since the knife angles are larger (not chisel ground), as well as the blade not being totally fixed
with respect to the object being cut; which in a hand pruner it almost is.



Cliff has suggested using 1095 at max hardness.
I am certain this would be a great improvement to the commercial "buttery" blades but likely not able to handle "dirt" branches and small dried knots.

Any further thoughts are appreciated.
 
Once you know better, it does hurt to see the mediocre quality that is passed off to the consumer marketplace. The average Joe simply won't pay up, and so good quality cutting tools are indeed hard to find.

Here is one cheap idea... Fiskars (Gerber's parent) does make an upgraded shear.

http://gardening.fiskars.com/show_product.html?SKU=8109&main=Garden Tools

I bought a pair of their bypass loppers with this blade technology, but sure don't know what they've done to increase the cutting edge durability. It just looks chrome plated to me, but I'm guessing hard chrome (~Rc60) wouldn't last long before it flaked off under stress unless they put it on thick and with a really good process, so that probably isn't it.

Are my loppers "way better" than others? I dunno. Haven't used them enough or side-by-side with say Corona loppers to be sure. I only cut a couple dozen branches, bought them after having trimmed my 4 Crape Myrtles this spring with a borrowed pair of Sears loppers that were cr@ppy. [Obscure Frank Zappa reference: "Now, is that a real poncho? Or a Sears poncho?"]

I bought my Mom a pair of the same Fiskars loppers if that is any indication I thought they were a reasonable design and value, mostly because they do have some built in mechanical advantage and she's getting up there in years, and she likes them mechanically (and is terrible about maintaining her carbon steel Felco's blades).

Anyway, these shears might be worth a try if the price if you can find them, or just buy on Amazon for around $17. I'm afraid you could spent WAY too much chasing custom made blades from a maker...especially since they are typically curved blades and he'd have to do some work to make them fit right.

Heat treating yourself would be a fun experiment but I had the same immediate thought Jeff Clark did...warpage... and that'll kill the bypass pruners pronto, maybe not the anvils. Great experiment though... let us know if you try it out, for better or for worse.

http://www.amazon.com/exec/obidos/t...63297-3128753?v=glance&s=home-garden&n=507846

The Fiskars UltraBlade™ Pruner sets a new standard for lasting sharpness and corrosion resistance, staying sharp 5 times longer than standard pruners. The UltraBlade™ process increases blade hardness and is proven to maintain edge sharpness, and the UltraBlade™ coating will never wear off. The UltraBlade™ will cut with less effort far longer than either a blade with no coating or a non-stick coated blade. This means more comfortable use, less fatigue and less need for sharpening. In addition, UltraBlade™ offers corrosion resistance greater than that of stainless steel.


Features
Stays sharp 5 times longer
UltraBlade™ coating will never wear off
More corrosion resistant than stainless steel
Less fatigue on hands
5/8" cutting capacity
Lifetime Warranty
Click to expand...


And if you try the Fiskars UltraBlade shears and they beat the Felco's, let me know... I have some Felco's, but they are pricey, so finding an improved tool at 1/2 the cost speaks to me.
 
In regards to the knots, it would depend on how much twisting there is going through them. If the action is very chisel-like, with no snapping around the edge, then it would not be a problem. This is a geometry more so than a steel issue however. As for dirt, with high abrasive content, you might see an advantage in going to M2. However the cost from 1095 to M2 is going to be fairly large.

-Cliff
 
I doubt bypass pruners could ever be expected to hold up well cutting dead branches/shoots, especially with a lot of accumulated dirt; anvil pruners would be the better choice for such work. See:

http://www.thisoldhouse.com/toh/knowhow/yardandgarden/article/0,16417,435550-2,00.html

I actually find a Japanese tree saw much handier than pruners or loppers for dry/dead/dirty wood (between drought and heavy off-season snow storms, we've seen a bunch of that kind of work around here lately.) It's amazing how these saws hold up, even cutting roots from sandy-clay soil. On smaller, dry branches, just score and snap.

BTW ... my Felcos are a pair I found, and had some pretty extensive damage to the cutting blade which I had to clean up; this is how I know how soft the steel is. Sharpening a tool like this, you really gain an appreciation for how an edge has to be profiled in order to minimize binding, without being made too weak. When I first sharpened them, I didn't add a secondary bevel, and while they cut like crazy at first, the edge quickly rolled. Adding the ~35 degree secondary bevel -- only slightly more obtuse than many wood chisels designed for controlled, precision work -- didn't degrade initial performance much, but improved durability dramatically.

Interesting topic and discussion -- thanks to all who contributed.
 
Yes, Japanese saws with HSS edges work great for cutting small hardwoods. They excell in abrasive and dirty material. The steel is after all designed to cut metals.

-Cliff
 
It sounds to me that commercial users in the US have gone more to the replace often, inexpensive side of the street for pruning shears--similar to the knives employed for meat and fish processing.

There are several vendors of Japanese garden tools on the net. I'd bet that that a quality pair of Japanese shears is constructed with the thought of providing a lifetime of service. Bonsai and Japanese gardening place great importance on getting the cleanest cut possible, so the tools are likely to hold a good edge.

Here's one such site:

http://www.stonelantern.com/masakunishears.html

TM-2001-01.jpg


Masakune $175

TO-101LG-01.jpg


Okatsune $49 or $59 depending upon size.

There is also a variety of loppers and heavy-duty snips on the site. No anvil pruners though.
 
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