When using a secondary bevel does the primary bevel need to be sharpened past coarse?

[Aaron Karp]

I was sharpening my block plane iron yesterday and needed to reestablish the primary 25° bevel. For this I used 120g sandpaper. Then I established a secondary bevel on a 400g stone and proceeded to hone and polish the secondary bevel on 1000g and 5000g stones. The primary bevel looks rough, but the secondary bevel is shiny and sharp. Did I do this correctly?

[Kent A Bathurst]

Primary bevel never gets near the wood. Does the 2dary bevel do what you want in use? Yes? Then you're done. Making the primary pretty is a waste of time.

[Edward Weber]

Yep, that's all you need to do

[Robert Hazelwood]

No it does not. In fact 120 grit is a bit fine IMO, I use 80 or 60 grit. Gets the job done even faster. And if you're using a power tool to grind, you really want to avoid finer grits because they generate more heat.

[Reed Gray]

I am now using an 80 grit CBN wheel to form the primary bevel. My sharpening platform seems to be at about 23 or 24 degrees, but secondary bevel is at 30. I do take the first few strokes on the secondary bevel with 220, then maybe 400 to get rid of the deep 80 grit scratches, then on to the high grits. I generally don't sharpen the secondary bevel all the way to the cutting edge/secondary bevel, so in that case, I just start at 4000 or 8000 grit. 80 grit scratches are pretty deep and I would want them gone. A toothed blade does have its uses, but not for fine finish cuts. Supposedly grits above the 600 to 700 grit range are not visible to the human eye.

robo hippy

[Jack Dover]

Yes, you're doing it right.

Polishing is required for the cutting edge only. It is required because if a cutting edge sharp, but jagged - the sticking out bits will crumble out taking surrounding grains out, quickly degrading the sharpness. Kind of like a dead twig can break out a chunk from a trunk, leaving a deep tear out. You could try it, just remove a wire edge on a coarse stone. Counterintuitively the blade will shave, but it will go dull pretty much instantly and you will see damages to an edge with a naked eye.

[Chuck Hill]

I am not sure that I understand. For "I generally don't sharpen the secondary bevel all the way to the cutting edge/secondary bevel" did you meant to type "don't sharpen the PRIMARY bevel all the way to the cutting edge"

Before you go to the CBN wheel, the secondary bevel is at whatever grit you normally finish at, or strop to if you strop. When you regrind, you should get close to, but not grind away the existing secondary bevel. You don't want the grinding to shorten the blade. Then you just continue honing the secondary bevel as usual. Is that what you meant?

[John C Cox]

My experience has been that edge damage is very slow to hone out. Often the problem isn't just the wear on the bevel. The back sees wear and edge damage as well.

Grinding back to fresh steel, including wiping out the secondary bevel, lets you clean off the worn steel on both the bevel and the back. Re-honing the secondary bevel then takes only a few moments.

Since I'm now power sharpening and then buffing the edges, I just use one angle. 25 for paring and 30 or 35 for chopping. The buffer takes care of the rest.

[Reed Gray]

Been out of whack for a few days, viral infection the doctors told me. I even cancelled front row tickets to see Ringo Starr and his All Star Band last night. I do sharpen the primary bevel up almost all the way to the secondary bevel. The part that wears the most is the secondary bevel, and we just sharpen that on the really fine stones.

robo hippy

[Tony Shea]

I would recommend using something coarser for the primary bevel. This bevel doesn't see wood therefore doesn't need to be fine. I also don't bother using something as coarse as the 400 grit stone once you start on the secondary bevel. The first time you hone your secondary after grinding, there is very little steel that needs to be honed. Starting with your middle grit stone, (1K grit in your case and 5K in my case) is plenty coarse enough to start creating the secondary bevel. This will give you a much smaller secondary bevel after grinding your primary therefore lasting longer between grinding sessions. I used to work the initial secondary bevel with coarse stones thinking I needed to remove the grinding scratches. Removing these scratches is still very necessary but using a much finer stone on that tiny surface area is much easier than one would think.

[Derek Cohen]

I was sharpening my block plane iron yesterday and needed to reestablish the primary 25° bevel. For this I used 120g sandpaper. Then I established a secondary bevel on a 400g stone and proceeded to hone and polish the secondary bevel on 1000g and 5000g stones. The primary bevel looks rough, but the secondary bevel is shiny and sharp. Did I do this correctly?

Hi Aaron

I create the primary bevel on a bench grinder. The finish at the bevel edge is important.

Hollow grinding on a 180 grit CBN wheel is noticeably smoother than a 80 grit wheel, but both are a lot finer than a white wheel. Further, my set up uses a Tormek guide for holding the blade. The result is a finer and straighter edge. The relevance of this is that it requires LESS work to hone the micro bevel. The smoother edge will also likely last longer owing to less serrations to create micro chipping.

Regards from Perth

Derek