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Blade Testing

Steve Elliott

>All cryo does on A2 is reduce the size of carbon bits so the blades will sharpen to a bit finer edge and not be so brittle.

When steel is heat treated it forms grain that resembles grains of sand packed together. Finer grained steels are supposed to have better edge holding properties.

In addition to grain, some alloys form carbides. If the carbide particles are small and evenly distributed, they increase the steel's wear resistance. Large carbide particles unevenly distributed can make the blade hard to grind without imparting good edge qualities. I don't know if cryo treatment affects the size of carbides. One of the advantages of particle metallurgy steels is that a higher percentage of carbide-forming metals such as vanadium can be used without the problem of carbide segregation, which causes large carbide particles.

Does this testing include cryo treated blades? Would a less brittle finer edge at this acute angle hold an edge better and be easier to sharpen? Did this breakdown at 25 deg occur in dense or soft woods.

I had one of my CPM 3V blades heat treated to Rc 59 instead of Rc 61 so that it would be less brittle. That blade at a 25 degree bevel angle looked like this after it was used to plane Port Orford cedar, which is the softest of my test woods:

The largest chip is about .008" wide. I began increasing the bevel angle to avoid this sort of edge failure. In my experience, bevel angles under 29 degrees or so don't hold up when used in planes with bed angles of 45 to 48 degrees. They probably hold up better in low angle planes.

One of the questions I'm trying to answer is whether some types of steel will take a sharper edge than other types. I've heard from several knowledgeable sources that high carbon steels will take a sharper edge than most alloys. My attempts to detect differences in "sharpest possible edges" using different alloys has been unsuccessful. On the other hand, I've found it possible to put wickedly sharp edges on all of the blades I've worked with.

As for the actual results of my blade testing, I haven't yet done enough planing and comparing of results to have anything solid to report. I've learned a lot about sharpening and the various ways edges can fail, and have produced some silky-smooth surfaces on wood. But I'm holding off posting results until I trust my procedure.

Re: Yes!Yes!Yes!

Lyn J. Mangiameli

>"My attempts to detect differences in "sharpest possible edges" using different alloys has been unsuccessful. On the other hand, I've found it possible to put wickedly sharp edges on all of the blades I've worked with. "

I'm certainly no metalurgist, but I sure have a lot of experience sharpening plane blades and evaluating the surface they leave when put in a finely tuned plane. I've tried almost everything, Japanese laminated blades, English laminated blades, A2 and A11 blades, M2 and M4 blades, O2 blades, and a bunch more that don't immediately come to mind. When sharpened with the appropriate media and technique, I just don't find any reliable differences in performance when freshly sharpened. Some blades have longer edge retention for a given angle, but all quality blades I have examined can be taken to an edge that performs comparably.

HIJACK: Lyn, how is your hand mending?

Don Thompson - Cutler Ridge, Florida

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hand mending

Lyn J. Mangiameli

>Hi Don,

I'm out of the casts now, and the bulk of the bandaging is now reduced. I can type fairly well (as you have likely noticed)--at least relative to how I could before. Alas, I can't apply much force through the hand right now (mostly because of some deep rips in the palm and by the thumb that are still healing), so I can't really plane, or hold turning tools, or weight lift (and I'm crankier because of it).

Perhaps the good thing is that now that I can type but can't do the other things, I'm more motivated to sit down and get the writing out of the way that is long overdue.

Re: hand mending

Don Thompson - South of Miami

>I am saddened by the cause of the speeding up of the release, but I sure will be glad to see your latest plane paper.

Get well soon!

Re: Yes!Yes!Yes! *LINK*

Brent

>There are two questions here, both of which are important.

Steve showed a blade with a chipped edge. Earlier in the thread I think there was a suggestion that the edge rolled over. I don't think steel this hard can roll over - I suspect it actually chipped out.

Steve reports chip out on all his blades at low angles. In my experience with about 35 different blades, only A2 and the Holtey blade chipped out. Standard high carbon steel blades have never chipped out for me.

Lyn's point about sharpness is somewhat different. I agree that all the blades I have tested can be brought to the same shape - you can get a full width edge with the same included angle. So, the initial state is the same.

However, if the edge quickly chips out (carbide drop out), the starting point is rapidly lost so the distinction is unimportant.

Brent

PS For a whole lot more on sharpening plane irons with lots of microscope pictures, check out my sharpening pages.


http://www3.telus.net/BrentBeach/Sharpen/overview.

Carbon Steel Blades & Chipping

Steve Elliott

>Carbon steel blades can chip, although they resist it better than most other types of steel.

In my testing I've used an old William Marples laminated blade as a benchmark for the performance of traditional steels. It's a very old blade, judging by its appearance, and I believe the body of the blade might be wrought iron instead of mild steel. The cutting edge grinds very slowly and takes an edge well using waterstones.

Here's an image of the edge, sharpened at 32 degrees, after planing 100 lineal feet of cherry:

After I had planed this piece of cherry with several blades, I found that most of the blades had chips near the right side. Looking very closely at the cherry, I found a very tiny pin knot that must have caused the chipping.

Carbon steels such as W2 and O1 have shock resistance (toughness) of about 80 foot-pounds in the Charpy V-notch test. O1 tests at about 40 ft.-lbs. and A2 tests at about 20 ft.-lbs. CPM 3V is somewhere between A2 and O1, but the test results I've found for it were from the Charpy C-notch test, which gives numbers that can't be compared directly.

My own experience confirms these rankings. Even the toughest steels will chip if the bevel angle is too acute for the hardness of the material being planed.

Correction: In my first post, I said incorrectly that the chip in the edge was the result of planing Port Orford cedar. It was actually caused by planing soft pine end grain.

Hock's chip

bill tindall

>I made a low angle plane fitted with a carbon steel "woodie" iron. With a bevel angle of some where between 25-30 degrees it chips when planning end grain. It seems that end grain is hard on edges.

You're back? how was trip?

bill tindall

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Re: Carbon Steel Blades & Chipping

Brent

>Great picture.

My testing seems to be omitting an important aspect of plane blade durability. I do all my testing on knot-free air-dried douglas-fir boards that came from a single tree.

With this test material I have never had a chip with standard high carbon steel blades, but HAVE had chips with most A2 blades (except a CRYO treated Hock blade - but I am not going to restart that thread here).

Thanks for the numbers on toughness.

Brent

Planing Douglas Fir

Steve Elliott

>Brent-

Douglas fir may be one of the best species to use for blade testing because the rings have very soft and quite hard wood side by side. I've also found it to be much more difficult to produce a good surface on Doug fir than most domestic hardwoods. If I ever get a low angle plane, I hope that will help.

After doing some work on blade testing, my hat is off to you for all you've done. My results so far generally confirm yours, but mine are so anecdotal that I don't trust them yet. Most of what I've learned so far is about the drawbacks of my sharpening technique and the difficulty of working out a reliable testing procedure. It's been interesting and fun, though, which is why I'm doing it.