Uddo Puukko : Enzo/O1


Knives :
  • Uddo Puukko

This review consists of :

Introduction and Specifications

Maker's YT page , basic specifications :

This is basically :

The Enzo blades are modified in various ways by Uddo :

A quick scan of YT shows the following general impressions :

In general given the makers practical approach to knife design/building it would be expected that the ELU would be pleased with the end product as long as they were looking for performance based expectations.

Extended Use

With any single bevel grind, it is almost immediate to do some wood carving as that is one of, if not the most promoted usages for that style of grinds. It is also obvious that style of grind (single bevel) is common in many wood working tools such as chisels and plane blades and it currently is extremely popular so much so that it is often argued as the only choice for wood work :

A Scandinavian, or scandi grind is a great grind for most if not all small woods chores, from carving tent stakes to making fuzz sticks. No other grind gives you the control, or the keenness of a scandi grind.

Now while this position may be a bit over the top, there is no doubt that such knives are commonly used for wood work. In regards to this knife there was some concern about the fact it was a three fingered grip and that might be a concern for fatigue, but with some use (see the video on the right) it was obvious that unless the amount of work was extreme (much more than 1000 slices) there was no real concern about fatigue. However there were some unfinished spots on the handle which left it fairly squarish and reduced comfort. As the handle is just epoxy these issues are easily resolved by a little sanding and then buffing.

Beyond wood carving, looking at this knife, given the narrow and short blade, It might be thought of akin to being a paring knife, however it has to be taken into account that :

As noted further below, it was actually quickly modified to a full/zero grind from the initial partial height grind, but even with this modification it is still a very robust knife. Consider that the primary grind, even when full is ~6 dps due to the thicker stock on the very narrow blade.

In short, this knife has a fairly high durability/strength given the cross section and so often gets used for difficult cutting. As an example of such it was to remove some sods for a walk-way. Now there are specialized knives for sod cutting (which are basically sharpened narrow trowels) but one of the nice things about a small neck knife is the fact it is almost always there when it is needed.

Even in this fairly demanding work the knife was :

As noted in the video on the right the only real downside in that type of heavy cutting is the small size which tended to limit depth of cuts.

Interesting enough on cutting up sods the narrow blade with was a negative as in pry up the sods it would often easily break them. In such work a much wider bladed knife like the AK-47 discussed in the video is more productive.

In the kitchen, as an actual paring knife, the Uddo Puukko works exceptionally well for peeling type work as it is :

and has a very acute edge and a steel which readily takes and holds a high polish. With a high grit finish the edge it will literally almost float through the skin of a potato and easily peel a turnip. However for coring and similar tasks a more precise / slim tip would be preferred but outside of a dedicated paring knife, this works in general very well.

Moving past paring and onto utility work :

Then the performance starts to be lacking but this is nothing more than attempting to push a paring knife outside where a paring knife is designed to be used. The knife simply lacks the length to make deep cuts and the heavier wedge shaped section due to the narrow blade on the moderate thickness stock also increases the force required to less than efficient levels.

Sheath

The sheath is a simple fold over style with a small drainage hole. There is no prominent thumb ramp however the lip has been flattened to give purchase.

There are a few issues :

The aesthetic issues of the edge and throat can be evened out with some sandpaper but are purely cosmetic. However the inability to draw the knife due to the very high retention of the sheath is a functional problem.

As Kydex is a thermoplastic it can be easily formed with heat. However before that was necessary the retention issue was resolved as the blade was later fully flat ground and this lowered the retention sufficiently to allow a smooth draw.

Uddo also uses a unique method of attachment of the cord to the sheath which is not to tie or knot the cord but to melt the ends. This has :

After carrying the knife for a couple of weeks the melted ends of the cord wore enough to allow the cord to slip out from the holes and release the sheath. Periodic inspection of the melted ends is critical to keep the attachment functional.

Grip

Ergonomics : the knife has an oval shape and works very well in a sabre grip (thumb on spine) as well as a forward pinch grip. As noted previously there were a few squarish spots on the handle (the handle/blade transition area) and these were lightly sanded and buffed to smooth them out.

The very nicely rounded spine is an asset in most grips and unlike many knives which often at best just chamfer the spine this one is fully rounded similar to Reeves for example and thus is very comfortable.

The handle could use a little finishing work in general though if aesthetics were a concern. However as it is just an epoxy finish it is very difficult to maintain such a high level of finish as it is easily scratched, cut or abraded.

However hammer and reverse grips are not as comfortable in use. While they are certainly function there are issues with :

The partial length grip puts a lot of force against the ring finger in heavy force and for such heavy work in general a full sized grip is far more optimal, especially for extended work.

The narrow throat due to the index finger choil also makes such grips very sloppy/open in that region and reduces comfort and security. Again though such smaller knives are in general not intended to be used in such grips with such heavy force normally.

Security : the knife has decent security in moderate dynamic cutting through :

and it also has a lanyard hole which can be used with a loop for secondary retention in extreme circumstances.

The only thing to be aware of is that the index finger choil is not nearly as deep as is found for example on Fred Perrin's knives. It is only deep enough so that the guard is about half height on the finger and thus in a very hard stab/thrust then secondary retention through the lanyard is a sensible option.

The short and shallow nature of the guard can really be noticed in an ice pick grip which is commonly used in very heavy stabbing and/or digging. However due to the :

this grip is awkward at best.

Durability : one of the common concerns about the durability of the handles is heat considering that it is an epoxy based grip and it is known to boil many epoxies. Uddo shows clearly that the handles he uses are capable of handling extended soaks in boiling water without concerns YT and as well has subjected them to extreme impacts YT. However in this particular one, the epoxy used is fairly susceptible to abrasion and cuts and tends to needed to be sanded/buffed on a semi-regular basis to keep it smooth.

Construction : the construction of the handle is one of the most curious and interesting parts of the knife. Now Uddo may not be the first person to use cord + epoxy to make a handle but he certainly has popularized it on YouTube.

The procedure is quite simple and he has documented it on many videos. He uses an underlayer of cord and doesn't simply soak it in epoxy or give it a light coating as is common. Instead Uddo completely covers the cord to such an extent that it is completely and evenly covered by Epoxy and at times uses tang extenders to make sure the handle is of sufficient length.

Steel

The following specifications cover O1 Tool Steels :

Nominal composition of O1 :

As a bit of detail on the composition, as noted in the image on the right, it only requires a maximum of 0.6% carbon to produce maximum hardness, above that there is very little increase and there are issues with retained austenite and formation of plate (vs lathe) martensite. Why then does O1 have such a high level of carbon?

The extra carbon will form carbides which are much harder than the steel (martensite) such as cementite, and more importantly since O1 has a small but significant amount of alloy carbide formers in Tungsten, Vanadium and Chromium, all of which will tie up carbon in the formation of carbides. The carbon needs to be increased above 0.6% to ensure that a free amount of carbon is left to go in solution in the martensite to enhance the hardness.

In regards to the carbide formers, the tungsten and vanadium are mainly there as they will not dissolve in the austenite and thus they pin the austenite grains as they form and thus keep the grain very small which increases the strength and toughness of the steel. These very small and very hard carbides are much harder than the martensite and the cementite 1 and thus will contribute to the low stress abrasive wear resistance over a pure carbon steel such as 1095. However to really make this significant then a lot more Tungsten is needed, several percent such as steel in the cold work grades such as F2. 2

The other significant alloy influence in O1 is the manganese which is very beneficial to steels in many respects (it is a deoxidizer) and chromium, and to a lesser extent the silicon. These elements all increase the hardenability, or ease of forming martensite. This is why O1 can oil harden but 1095 for example needs a much faster quench and is usually water hardened. For the knife user, this makes little effect, but for the knife maker, not having to deal with the extreme quench of water and the risk of cracking can be of benefit.

The chromium in the steel increases the hardenability by reducing the high temperature diffusion reactions. This means as the blade cools, the chromium stops pearlite from forming The manganese addition has a similar effect, it also reduces the formation of pearlite, but it does so in another way. manganese expanding the austenite phase to being stable (existing) lower temperatures. This ideally prevents the ferrite from forming until ideally the temperature has been reduced by the quench to the point martensite starts to form. These alloy additions to O1 over the plain carbon steels and the effect they have on the reduction of the pearlite and thus the increase in the hardenability can be readily seen in the TTT curves to the right.

O1, like most of the high carbon or high alloy steels can benefit from an extended quench where the steel is taken to below room temperature. The main reasons for this are the :

The combination of these two effects can produce an increased hardness of 2-3 HRC points and an increase in low stress wear resistance by a factor of 2. 2a .

What does all of this mean as to how the steel performs? As always, it is of benefit to look at some comments/feedback on steels from the woodworking industry as it is a very common chisel and plane steel. In general O1 is considered an entry level steel for such materials when compared to White, Blue and HSS chisels using M2 or similar steels. All of these materials will have a significantly higher carbide content, but still retain a very fine, well distributed carbide network as noted in the image on the right. 3 The apex stability in M2 and similar steels is therefore still high enough they tend to blunt by slow wear and can maintain a high sharpness.

The PM-V11 and the White Steel really do deliver. The gap between them and the A2 and O1/HCS is very large.

Now a frequent point of contention in such materials is O1 vs A2 and in general the argument is A2 will make a stronger and more wear resistant edge but it is harder to grind :

A2 is a great steel that offers a real improvement in edge retention. O1, on the other hand, is still preferred by many for its relative ease of sharpening and its ability to get sharper.

However the difference in these materials in terms of abrasive wear resistance is actually quite small and they both have the same working hardness ranges and maximum obtainable hardness. In practice then what is often seen in terms of one out performing the other is dependent more on which manufacture made which chisel in a particular steel and the random stresses on it in a particular use. Brent Beach for example compared a large range of planes in various steels and while the HSS blades in M2 did consistently offer superior performance the performance of A1 vs O2 was just a random spread around each other :

  • Lee Valley A2 , 6
  • Lie Nielsen A2 , 6
  • Lee Valley block plane A2 , 12
  • Lie Nielsen #62 O1 , 18
  • Hock O1 , 9
  • Knight O1 , 6

  • While the data show a weak increase in performance of A2 over O1, the numbers listed (which are the wear bevel sizes) differ in the random spread much larger than the difference between them so there is no statistical significance. Beach was also doing a very controlled comparison, in normal work it is even more unlikely a consistent performance increase would be seen unless careful observations were made over a very long time period.

    In regards to edge retention on this knife, it was used for extended slicing comparisons on 1/2" hemp and cardboard and performed well, similar to other steels in its class in regards to generally blunting by slow wear and resisting chipping and significant deformation. 4 , 5 . In order to have the performance significantly exceeded in regards to edge retention it was necessary to step up to steels such as Elmax and M4, or use a steel similar to this one, but hardened differently such as customs in 1095 which are at maximum hardness, 66/67 HRC. Of course while the edge retention slicing abrasive materials is higher in those examples, they trade off grindability and toughness to obtain the higher strength and wear resistance.

    An example of the kind of tradeoff in terms of toughness and how it influences performance can be seen in the comparison of various steels cutting used carpet6 . Carpet, especially when used, is a very abrasive material and it has grits large enough to seriously wear a steel edge, and since it is hard to cut the forces involved can also cause fracture as well. In such cases, picking a steel which has the highest hardness and carbide volume might not always perform the highest.

    As the work is pretty demanding on an edge and can cause fracture, there is also a significant requirement for toughness/durability. The O1 blade from Uddo shows its versatility here as it could easily do extended slicing without any significant damage and just blunted by slow wear. The fact that it takes no visible damage in such work has a significant effect on the ease, or speed of resharpening.

    In terms of performance, in regards to the steels used :

    the top performance in edge retention was seen in S30V. However the O1 blade is significantly easier to grind and when the two are combined to represent a kind of edge retention - efficiency measurement then the O1 is ahead of the S30V. Now of course if the knife is power sharpened or very coarse / high end stones are used to grind it, then this kind of measurement is moot as grinding speed can be rapidly reduced in such methods.

    The same kind of benefit was seen to an even greater extent when the knife was used to cut up some sods alongside a few other folders. 7 :

    As noted in the chart at the right it was among the fastest to sharpen as it again took very little damage and the steel has a high grindability.

    In regards to sharpening, O1 in general gets high praise for ease of sharpening, not only as noted by the woodworkers as noted previously but by knife users as well. It is one of the easier to sharpen steels possible as it has :

    As this blade is hardened for high durability, then it compromises a little on the edge retention in light use for performance in light use as noted in the above. However This means that in general the chip resistance is fairly high (compared to steels such as D2, TS-34, 10V) and in heavier use it can excel where such steels would chip. In general due to the combination of toughness and strength the edge tends to blunt by slow wear as noted in the image on the right which also increased the ease of sharpening by reducing the necessary grinding as seen in the carpet cutting previously.

    This knife came with a single-bevel grind, often called a Scandinavian grind. As with most single bevel grinds they are often considered to be easy to sharpen due to the built in sharpening jig of the very wide bevel. As the bevel is so wide it is very easy to keep it flat on the stone so it is often preferred by novice sharpeners.

    He still wanted the short bevel grind and explained that most people who attended his courses weren’t necessarily “knife people” and that it would be easier for them to sharpen if they could lay the whole bevel on the hone.

    The downside of having to sharpen a very wide bevel is the time and effort required to plane down that wide strip of steel hence why such grinds should be in a easy to grind and tough steel. However in this particular knife the primary grind was not true flat and uneven from one side to another. The first few attempts to sharpen the knife flat to the stone were not overly productive. Since the bevel needed to be flattened anyway, in order to simplify sharpening and increase cutting ability and future ease of sharpening the grind was converted to full flat.

    This also allows a greater range of optimization of :

    as the high primary grind can be strengthened with a small secondary or even micro-bevel at a higher angle to drastically increase the strength and durability of the edge with only a minor decrease in cutting ability.

    As this is an easy to grind steel many modern stones can actually break down too fast as they are often optimized to cut harder to grind steels. In that case an alteration of normal sharpening methods can be used to prevent excessive wear of the stone.

    The image on the right was used to minimize the wear on a 700X Bester by :

    This starts the stone cutting fast for metal removal during the initial shaping. However as the stone dries then the rate of material removal from the stone slows. This kept the stone wear to a minimum during the 300 pps as seen from the minimal abrasive wiped off on the paper towel.

    As for corrosion resistance, while O1 has a small amount of chromium as noted in the above, it is no where near the amount necessary to produce significant corrosion resistance. It will naturally form a patina even in mild environments and needs significant protection against rust.

    Overview

    A few key details :

    Cutting performance is similar to a standard Mora as it initially had the same grind. It was later reground to full flat to increase :

    Comments and references

    Comments can be emailed to cliffstamp[REMOVE]@gmail.com or by posting to the following thread :

    and/or the YouTube Playlist.

    Most of the pictures in the above are in the PhotoBucket album.

    1 : Hardness Tables, Ted Pella, Inc.

    2 : Steel-Grades.com, F2

    2a : Wear resistance improvement at various stages of cryogenic treatment of o1 steel, P. Sekhar Babu , P. Rajendran

    3 : Record of Microstructures

    4 :Edge Retention slicing 1/2" hemp, 6 micron, 25 dps micro-bevel

    5 :Edge Retention slicing cardboard, 25 micron, 15 dps micro-bevel

    6 :Edge retention slicing carpet with 3Cr13, O1, K390, S30V and 121REX

    7 : Sods : Uddo, Temperance, Surefire, AK-47


    Last updated :
    Originally written: 01/07/2013
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