Tapered Iron Hollow Grind Question

[gregbois]

I am restoring a wooden jointer plane with a 2" wide tapered laminated iron.  

I have two basic questions:

1.  What is the appropriate bevel angle for such a plane iron?

2.  Should I hollow grind the bevel?

I realize these two questions are linked, as I surmise that the lower the angle of the bevel the less likely it is that a hollow grind would leave sufficient heft in the blade.  I'm also inclined to treat the blade as akin to a Japanese iron, which you never hollow grind, allowing the thickness and the softer steel to brace the hardened steel edge.  

Any wise and sage words of advice are greatly appreciated.

Thanks!

[Admiral]

I am restoring a wooden jointer plane with a 2" wide tapered laminated iron.  

I have two basic questions:

1.  What is the appropriate bevel angle for such a plane iron?

2.  Should I hollow grind the bevel?

I realize these two questions are linked, as I surmise that the lower the angle of the bevel the less likely it is that a hollow grind would leave sufficient heft in the blade.  I'm also inclined to treat the blade as akin to a Japanese iron, which you never hollow grind, allowing the thickness and the softer steel to brace the hardened steel edge.  

Any wise and sage words of advice are greatly appreciated.

Thanks!

I would go between 25 and 30 deg on the bevel; you likely have to square it up so there would likely be a lot of removal, I'd hollow grind (light passes, quenching often) then flatten the hollow on stones once you have the square working edge established.  Others may have different opinions.

[JimReed@Tallahassee]

Admiral is right. I bevel my plane irons from 25-35. It depends on the hardness of the steel and the characteristics of the wood you are dealing with. Softer blades don't like low angles and tough wood.

I also hollow grind every sharpened edge in my shop and have never had a chipping problem. That goes for Japanese chisels, too. But I hollow grind only the first half of the bevel surface. Grinding takes time and cutting only happens on the very edge. YMMV

[Rick Barton]

Oh yeah, a hollow grind, especially on something as wide as plane irons, sure makes final sharpening and honing much quicker and easier. I also can't see a down side to the practice assuming you have a good, accurate way to do it. I use my Scheppach (Tormek clone) grinder for this which makes it quick, repeatable and best of all, easy. Plane irons I personally grind at 25 degrees tho steeper is good too. Its the lower than 25 degrees that can lead to edge retention issues in inferior steel.

[gregbois]

Thanks one and all.  Sound like 25 degree bevel is in the correct, as is hollow grind.  I can do that on my Tormek.  I principally am planing hard woods, maple chiefly.  So, I'll give it a whirl and see if I need to increase the angle.

Much appreciated.

Greg

[Timberwolf]

I am restoring a wooden jointer plane with a 2" wide tapered laminated iron.  

I have two basic questions:

1.  What is the appropriate bevel angle for such a plane iron?

2.  Should I hollow grind the bevel?

I realize these two questions are linked, as I surmise that the lower the angle of the bevel the less likely it is that a hollow grind would leave sufficient heft in the blade.  I'm also inclined to treat the blade as akin to a Japanese iron, which you never hollow grind, allowing the thickness and the softer steel to brace the hardened steel edge.  

Any wise and sage words of advice are greatly appreciated.

Thanks!

.............
I like hollow grinding and prefer to grind at the lowest angle the steel will allow before becoming too blunt..If that occurs to soon to suit me, I then micro-bevel it...Hollow grinding, if nothing else, presents less resistance to the flow of the shavings.

[Derek Cohen]

I am restoring a wooden jointer plane with a 2" wide tapered laminated iron.  

I have two basic questions:

1.  What is the appropriate bevel angle for such a plane iron?

2.  Should I hollow grind the bevel?

I realize these two questions are linked, as I surmise that the lower the angle of the bevel the less likely it is that a hollow grind would leave sufficient heft in the blade.  I'm also inclined to treat the blade as akin to a Japanese iron, which you never hollow grind, allowing the thickness and the softer steel to brace the hardened steel edge.  

Any wise and sage words of advice are greatly appreciated.

Thanks!

Hi Greg

Woodworkers have hollow ground their laminated blades for a very long time. I began hollow grounding Japanese bench chisels well over a decade ago, and have never experienced a problem.

If you are looking for the most efficient way to hone a thick blade - and these laminated woodie blades tend to get to 3/16" at the pointy end - then creates a micro bevel either on a hollow grind or a straight grind. This can take the form of a microbevel directly on a hollow, or a micro secondary bevel on the hollow or a flat primary bevel.

The bottom line is that the final bevel needs to be around 30 degrees. Only a primary bevel may be 25 degrees. If you do grind to 25 degrees, then you need to add a 30 degree secondary bevel. My preference is to hollow grind a 30 degree primary bevel, and hone directly on the hollow, using the sides of the hollow as a jig when free hand sharpening. If you use a honing guide, then you will be honing a secondary bevel (and may start with a 25 degree primary bevel).

Why 30 degrees? Because anything lower will wear more rapidly.

Regards from Perth

Derek

[gregbois]

Hi Greg

Woodworkers have hollow ground their laminated blades for a very long time. I began hollow grounding Japanese bench chisels well over a decade ago, and have never experienced a problem.

If you are looking for the most efficient way to hone a thick blade - and these laminated woodie blades tend to get to 3/16" at the pointy end - then creates a micro bevel either on a hollow grind or a straight grind. This can take the form of a microbevel directly on a hollow, or a micro secondary bevel on the hollow or a flat primary bevel.

The bottom line is that the final bevel needs to be around 30 degrees. Only a primary bevel may be 25 degrees. If you do grind to 25 degrees, then you need to add a 30 degree secondary bevel. My preference is to hollow grind a 30 degree primary bevel, and hone directly on the hollow, using the sides of the hollow as a jig when free hand sharpening. If you use a honing guide, then you will be honing a secondary bevel (and may start with a 25 degree primary bevel).

Why 30 degrees? Because anything lower will wear more rapidly.

Regards from Perth

Derek

Hi Derek,

I really appreciate your (as usual) insights.  I'm going to hollow grind the bevel at 30 degrees and sharpen, as I always do, by hand.  Never did get the hang of honing guides.

Cheers from Sunny Southern California

Greg

[Skip J.]

I'm going to hollow grind the bevel at 30 degrees and sharpen, as I always do, by hand.  Never did get the hang of honing guides.

Cheers from Sunny Southern California

Greg

Me neither... got the honing guides.. don't use'em...

[JimReed@Tallahassee]

My experience says that honing guides are useful but only as training wheels. Once you train yourself how to keep the blade moving at a constant angle, you can ditch the guide. Of course, the guide has its own learning curve. The result is that once you master the guide you don't need it anymore.