Plane blade edge durability

[Jim Watkinson]

I've recently switched to Hock's cryo blades but have been dissapointed in the durability in the edges. I'm working in fairly common woods like oak and maple and occasionally bubinga and do a fair amount of planning. I grew tired of having to touch up a blade very 5-10 minutes with the old tool steel blades supplied with my planes, so I switched to Hock's blades. After several weeks of work I'm finding that I still have to resharpen every 5-10 minutes due to edge degradation. On something like bubinga I've been getting no more than 40 short strokes before I'm back at the waterstones.

What experiences have other been getting with these blades?

[Jack Camillo]

that bites. haven't tried hock's, just LV and LN A2. I noticed that out of the box, and one initial honing by me (talking chisels and plane blades), the edges would degrade faster than expected. I was really bummed the first time, wanted to find a hardness tester and make a stink. but, after about the third honing, the edge lasts nicely. I wonder if there's something similar with the cryos - the new edge it comes with is brittle or something?

[Wiley Horne]

Jim,

Is the Hock 'cryo' blade the A2 blade? If so, what bevel angle are you using?

Reason I ask is that Steve Elliott, who is a careful worker, has done some testing on the edge durability of various steels at different bevel angles. He found that his A2 blade (which happened to be a Hock A2) chipped in cherry at honing angles less than 34 degrees. LN recommends an included angle of 35 degrees for their A2 chisels.

Here is a summary chart of Elliott's findings on edge durability:

http://bladetest.infillplane.com/html/bevel_angles.html

Wiley

[Marcus Ward]

A2 has a tendency to have minuscule chips in it rather than just going dull which may be what you're experiencing. Try a microbevel of ~35 deg and see how it does.

[Ron Brese]

When making irons, the primary bevel angle has to be ground prior to heat treating, the very edge of the iron is of course thinner than the surrounding metal and as a result takes a bit more abuse thru the heat treating process. For the same reason the thinner edge may also temper a bit differently than the thicker areas. This has the potential to make the first part of the edge a bit softer than the rest of the iron. You may find that it takes several regrindings before you get into the really good metal of an iron.


Ron Brese

[Mike Henderson]

When making irons, the primary bevel angle has to be ground prior to heat treating, the very edge of the iron is of course thinner than the surrounding metal and as a result takes a bit more abuse thru the heat treating process. For the same reason the thinner edge may also temper a bit differently than the thicker areas. This has the potential to make the first part of the edge a bit softer than the rest of the iron. You may find that it takes several regrindings before you get into the really good metal of an iron.


Ron Brese
Ron - why is it that the bevel must be ground before heat treating? Seems that you could grind the bevel after heat treating, especially if the grinding was done with water (or oil) cooling so as not to affect the temper. Of course, we grind the bevel after heat treatment when we sharpen the tool.

I got some Henry Taylor carving tools that had the same problem - the edge would fracture out of the package but the steel was fine after a few sharpenings. Other brands of carving tools don't have that problem so I assumed they ground the bevel after the heat treatment.

Mike

[rick fulton]

Wiley,

Thanks for the link. Very interesting findings.
Have to check it out further when I have some time.

rick

[Ron Brese]

Mike,

Removing that much material on a hardened piece of tool steel without affecting the temper would be very time consuming and would change the price of irons significantly. However if one does most of the grinding and leaves the edge somewhat blunt this helps considerably, this however makes for more labor input to bring the iron to sharp prior to shipping.

Ron Brese

[Jack Camillo]

yah, that's exactly what i was saying (but you put it so elequently, Ron! thanks)

[Jim Watkinson]

These are all very good replies and exactly what I was looking for. My current bevel on the blade that has been a problem is 25 degrees (block plane) and it sounds like this angle is inherently weak for an A2 cryo. I'll re-set the bevel to 30-35 and test it out.

I was not aware that the heat treating process leaves the first few mm of the blade weaker than the rest. It makes perfect sense though, considering the thinness at that point. When I change the bevel I'll give it an extra deep cut. I use paper on this work so there's no risk of heating the blade and damaging it.

Perhaps the Hock people would want to include a notation with their product about the early edge status and the issue about bevel angles.

I'll let you all know what happens.

[Eddie Darby]

These are all very good replies and exactly what I was looking for. My current bevel on the blade that has been a problem is 25 degrees (block plane) and it sounds like this angle is inherently weak for an A2 cryo. I'll re-set the bevel to 30-35 and test it out.

I think the suggestion of using a 35* angle was for bench planes, and not block planes.

After sharpening a few times things should be alright at 25*.

At 20* built in angle on a standard block plane and a 35* bevel on the blade, you will be cutting at 55* which is pretty steep.
If you have a 12* low angle block plane then the angle will be 47* which is still fairly steep.

One of the advantages of using the 'block plane', or it's bigger cousins from the 'Bevel Up Gang', is that you can go from attacking 'end grain' with a low angle plane, set with a low angle beveled blade, to nicely slice off the ends of the end grain, to a high beveled blade like say 50* to attack wild grain that changes direction quickly. All this range is possible with these block planes, and the bigger block planes on steroids because of their Bevel Up, BU, configuration.

Lee Valley knowing this sell their blades with various angles, 25*, 38* and 50*. Saves a lot on the elbow grease, not to mention the savings in not wasting abrasives. Very user friendly idea.:D

The trade off for all this flexibility is that you need to adjust your sharpening to compensate for the added wear that happens with Bevel Up planes. Easily done by just adding a very small 'back bevel' to the blade in the area of just a few degrees or thereabouts.

http://www3.telus.net/BrentBeach/Sharpen/bevel%20up.html

The up side to all this is that you don't have to lap the backs of the blades since you are putting a micro 'back bevel' onto the back of the blade.

Should add that I picked up a nice Ron Hock blade on Sale because someone returned it for just this reason, and after removing a little more metal it gained it's well deserved reputation back.