Thread: Bevel Up vs. Bevel Down edge wear

Curious: the flat side of a BU blade wore more than the bevel side?

So the bevel was 34*. What's the bed angle on these LN block planes?

I guess thinking about it there's less edge support on the flat side of a BU blade so it makes sense.

Oh dear! This thread could get worse that the politics ones

The wear is caused by lack of clearance angle in 12º bedded bevel-up planes. Wood fibers deflect ahead of the cutting edge and spring back when severed. There isn't enough clearance to allow the fibers to return to their position without rubbing on the back of the cutting edge. The more obtuse the bevel angle of the iron, the more deflection and the more spring-back and wear to the back side of the cutting edge. A dull iron will also exacerbate the problem.

The net effect is that this wear needs to be ground away at each sharpening and the edge doesn't last long. This adds considerable effort and labor to restoring a short-lived edge. The "ruler trick" only reduces the clearance angle more and adds to the problem.

G'day mate,

Would this be Mr. Larry Williams from 'Clark & Williams'?

Anyway, your explanation is highly appreciated. While I am not planning to purchase any bevel up planes, reading the blog post from Konrad Sauer did intrigue me on the comparisons between bevel up and bevel down planes.

Cheers

Gunn

Originally Posted by jimbur

Oh dear! This thread could get worse that the politics ones

"The differences between Big-Endians (those who broke their eggs at the larger end) and Little-Endians had given rise to "six rebellions... wherein one Emperor lost his life, and another his crown".

Read the replies on Konrad's blog.

The point I made there is, while wear is expected to occur on the back of the blade - which is does for both BU and BD blades - the amount of wear that he showed on his LN block plane blade is unusual. I have no explanation, but one simple observation is that if BU plane users all experienced wear like this, they would demand their money back. The unusualness of this wear was what brought Konrad's attention to the blade - keep in mind that he has used this plane for several years and not noticed wear such as this before.

The LN block plane has a 12 degree bed. Larry argues that "The wear is caused by lack of clearance angle in 12º bedded bevel-up planes". I would disagree with this. The wear occurs because wood wears steel when they they come in contact with one another. If it did not do so then we would have ever-lasting sharp blades This is Larry's (frequently cited) criticism of BU planes. Another equally cited reference is that of Leonard Lee (Rob's dad), who wrote that 7 degrees of clearance suffices. That leaves a good margin for error!

The bevel angle of the blade plays no part in this scenario (the article was about the wear on the back of the blade, not the bevel face). However bevel angles are important when one discusses BU versus BD planes. One big advantage of BU planes is the ease with which one may change cutting angles. In Australia, with our timbers that typically feature interlocked grains, the cutting angle is relevant. We benefit from planes with high cutting angles. Witness the popularity of planes such as the HNT Gordon range, which were developed for Australian conditions. The cutting angle becomes less important if you are not working with such timber.

Although there is no proof that BD planes cut for longer that a BU plane (all other factors held constant) that I am aware of, I would not be surprised that it was so. The differences are small enough to go unnoticed by the majority of woodworkers around the world. And even if it was a significant amount, I value the ability of a BU plane to work magic at high cutting angles. So wear is, frankly, academic.

That said, I am presently undertaking a very large research project into bevel wear using different steels (O1, A2, D2, CPM 3V) at different bed angles (12 degrees, 25 degrees and 45 degrees), different bevel angles (25, 35 and 50 degrees), and different cutting configurations (BU versus BD). Results include photos of edges magnified to 400 times. When will this be done? Don't hold your breath - at the earliest several months - as I said it is only of academic interest and I fit such projects (and reviews) in between building stuff. I'll keep you posted.

Regards from Perth

Derek

Originally Posted by Manuka Jock

"The differences between Big-Endians (those who broke their eggs at the larger end) and Little-Endians had given rise to "six rebellions... wherein one Emperor lost his life, and another his crown".

As opposed to the rest of us who just get on with eating them

Originally Posted by jimbur

As opposed to the rest of us who just get on with eating them

Didn't two nations go to war over which end of an egg to break?
Can you name the work of fiction in which this occurred?

Out of interest I will look forward eagerly to Derek's review.
I suspect that in the final wash-up there will be differences, but they will be so marginal that they will make little practical difference.
Cheers
SG

Originally Posted by Scribbly Gum

Didn't two nations go to war over which end of an egg to break?
Can you name the work of fiction in which this occurred?

Yes , I can .
Is there a prize ?

Originally Posted by Manuka Jock

Yes , I can .
Is there a prize ?

Me too. Do we have to share?

Ok. After you Jock

Half the answer each , ok Lilli ?

put. gulli dean

Jim , do we carry on or do we wait to see if there actually is a prize ?