Reason for secondary bevel ?

[mike stenson]

The references to plane irons were included because they can be sharpened in a similar manner. I always think of the "face" of a chisel or plane iron as the flat side of the tool, so the bevel side is the "back". Some people refer to them in the opposite way, the OP may be one of them, who knows. It helps top think that the face is what makes contact with the wood.

See, I am certainly one who refers to the flat / reference side as the "back". As in "flattening the back of a chisel".

[Rafael Herrera]

See, I am certainly one who refers to the flat / reference side as the "back". As in "flattening the back of a chisel".

You certainly don't put one of those terrible ruler trick "back bevels", do you? That's one of the worst suggestions coming out of the Internet's gurudom.

[mike stenson]

You certainly don't put one of those terrible ruler trick "back bevels", do you? That's one of the worst suggestions coming out of the Internet's gurudom.

on a chisel? nope.

my great-uncle was effectively doing that on his plane irons in the 1930s btw.

[Alex Shanku]

That's one of the worst suggestions coming out of the Internet's gurudom.

With a ruler that's 1/16" thick, it's about 1* of bevel and about 1/8" long. Surely there must be many worse suggestions out there

Also, I've never heard anybody refer to the flat surface of a chisel or plane as the "face", is this carry over from another trade/industry?

[Jim Koepke]

I've only used bench chisels always sharpened using Japanese stones completely honing the entire face, as you can imagine this process takes a lot of time & effort especially if there's a nick. I just ordered a set of mortise chisels (Narex) and reading about secondary bevels being the way to go. From what I gather the big advantage to a secondary bevel is you only have to sharpen a small part of the face which makes sense, the other is the edge will stay sharp longer but that part really doesn't make sense to me. Is there some science behind that or is it just expert wood workers and experience that claim this ? Either way I'm going to try the secondary bevel just for ease of sharping.
Thanks

For my bench chisels, a honing the entire face is preferred. If care is taken to not hit nails or get into other incidents to damage the blade it doesn't seem to take much more time to keep my edges sharp.

For mortise chisels some like a secondary bevel and others prefer a convex bevel. A convex bevel can have a higher angle flat bevel at the business end if one so desires. A convex bevel also lends some help when levering out mortise waste.

jtk

[Edward Weber]

[QUOTE=Rafael Herrera;3285926]The references to plane irons were included because they can be sharpened in a similar manner. I always think of the "face" of a chisel or plane iron as the flat side of the tool, so the bevel side is the "back". Some people refer to them in the opposite way, the OP may be one of them, who knows. It helps top think that the face is what makes contact with the wood.[/QUOTE

Saying the face (flat side in your case) is what makes contact is just confusing to me, as a chisel is used in bevel up or down orientation depending on the task. For a bevel down plane, it sort of makes sense.
106_BenchChisels_Explo_MD.jpg
Face and back have the same meaning, sure that's not confusing at all

[Rafael Herrera]

The references to plane irons were included because they can be sharpened in a similar manner. I always think of the "face" of a chisel or plane iron as the flat side of the tool, so the bevel side is the "back". Some people refer to them in the opposite way, the OP may be one of them, who knows. It helps top think that the face is what makes contact with the wood.

Saying the face (flat side in your case) is what makes contact is just confusing to me, as a chisel is used in bevel up or down orientation depending on the task. For a bevel down plane, it sort of makes sense.
106_BenchChisels_Explo_MD.jpg
Face and back have the same meaning, sure that's not confusing at all

When thinking of bevel down plane irons, it make sense to me. The flat side of the cutter is what is "facing" the wood when it makes contact. The maker's stamp on plane irons is also on the flat side, one more reason to refer to that side as the face. However, the maker's stamp on chisels are on the bevel side, so that fails.

A chisel wedges itself into the wood, so the comparison with a plane iron is not as good.

For the chisel, I've also seen the flat side called "back face", so presumably there's a "front face". Call it whatever you want, just don't expect everybody understand what you're referring to, as I do.

[Reed Gray]

A very common tool used on the wood lathes is a NRS (negative rake scraper). It is used mostly for very fine clean up cuts. The first one used was a skew chisel, and the bevel angles are in the 30 degree range on each side. A common 'rule of thumb' is that combined angles should not be more than 90 degrees. I didn't like the skew chisel variety because the burr was so flimsy that you would only get a few seconds out of it. I ended up with a 60/30 bevel, with the 60 being on the bottom. Current theory is that you need a certain amount of mass under the burr to support it as a cutting edge. I also prefer a burnished burr as being far more long lasting, and cutting finer than the grinder burr. This seems to hold up. As for flat work tools, the burr is honed off, with the exception of the card scrapers. I am one who 'has' to experiment, just in my nature. I blame my dad. So, if the edge is really bad, I take it to a grinder with a CBN wheel. The hollow grind issues consist mostly of a 'slightly more acute angle' on the cutting edge. I don't know how acute it actually becomes, but the amount is minimal, almost unmeasurable, and I don't consider it a real issue. Maybe later I might change my mind as I get more experienced. The Japanese style tools all have flat bevels, and tend to be slightly more acute than western tools. So, I have a few Japanese style chisels and some Japanese style hand planes. I actually got one set up correctly and can take paper thin shavings with it, well thinner than paper.... I will keep on keeping on with the experiments. I would guess that the main point of the micro/secondary bevel is that you are only sharpening that small part of the whole blade. Does it actually make the tool function better? Not sure. I do know some prefer a more acute angle, like under 20 degrees for softer woods, which goes along with the idea of different plane angles for different woods. I doubt I will run out of things that need more experimenting.....

robo hippy

[steven c newman]

I simply refer to either the Bevel Face or the Flat Back face....

And the bevel face is just that...and I just use a single bevel on ALL of my cutting edges...plane iron or chisels. K.I.S.S.
Now, get back to work, before this becomes "Just Another Sharpening Thread"

[Robert Hazelwood]

The only thing that matters for edge durability and sharpness is the angle at the tip. Doesn't matter how many bevels or what shape they are. If the tool needs to make deep cuts then thinning out the bevel behind the edge will reduce resistance versus a single bevel. For shallow cuts like a plane blade it doesn't matter.

For most things I prefer to have a primary and secondary bevel. I maintain the primary with a belt grinder as a flat bevel at around 20 degrees, then hone freehand a small secondary at whatever angle I need. I don't like honing a large surface. The only tools I sharpen as a full flat bevel are Japanese, because they look cooler that way.

[Edward Weber]

The only thing that matters for edge durability and sharpness is the angle at the tip.

The original point of the secondary bevel was to leave more material behind the cutting edge on plane irons, (bevel down) thus strengthening it, making it less likely to chip and increasing it's durability. It's less necessary with modern alloys.

This can be as simple or as complicated as people want to make it but there are valid reasons for and against secondary bevels on all cutting tools.

[Robert Hazelwood]

The original point of the secondary bevel was to leave more material behind the cutting edge on plane irons, (bevel down) thus strengthening it, making it less likely to chip and increasing it's durability. It's less necessary with modern alloys.

This can be as simple or as complicated as people want to make it but there are valid reasons for and against secondary bevels on all cutting tools.

For a given final edge angle, any sort of primary grind is only reducing material behind the edge, which is the purpose. If two 1/8" thick blades have a final edge angle of 30 degrees, which has more material behind the cutting edge- one with a full flat 30 degree bevel or one with a small 30 degree secondary bevel and a primary grind of 25 degrees? The second will have less, and technically be weaker, but outside of extreme usage the relevant area for durability is the very tip and a few thousandths behind it. That's where any chipping or rolling will occur. So the edge angle at the tip is really all that matters.

If you are thinking of taking a full flat bevel of 30 degrees and then adding a 35 degree secondary bevel - then I agree that would increase material behind the edge in the area that matters, and so it will be more durable. But the main thing is just that you now have a 35 degree edge instead of 30.

[lou Brava]

FWIW, I posted about secondary bevels on chisels. I had read Paul Sellers blog and He seems to be in favor of em & I didn't understand the reason behind it. Now I understand the concept after reading all the post. For me I use Japanese water stones I don't own a grinder & I will not be putting a secondary bevel on my mortise chisels, much simpler to sharpen a single bevel & it doesn't appear to be any great advantage having the 2nd bevel. I received my Narex mortise chisels a few days ago & chopped some mortises today, big difference from my bench chisels I shouda bought these a long time ago !
Thanks everyone

[Jim Koepke]

I received my Narex mortise chisels a few days ago & chopped some mortises today, big difference from my bench chisels

Yep, big difference.

jtk

[Charles Edward]

Reason? A touch-up can happen in only a few strokes on a very narrow spit of steel. Otherwise, you don't have to have them.