Plane iron initial tuning question

[Kevin Perez]

Hi everyone, long time member but infrequent poster here with a question. Since I began woodworking, I have followed the traditional recommendation that you polish the back of the hand plane blade and the bevel to a mirror shine. However, I'm thinking that polishing the primary bevel may be useless if you use a secondary bevel. What do you think?

[Curt Putnam]

IMO, only the secondary bevel needs to be polished. If the main bevel is grungy it should be cleaned up so that chips won't hang up. Anyway, I only work the secondary bevel and it works for me.

[Andrew Pitonyak]

I thought that the primary point of interest is that you want as nice as possible surface where they finally meet. So, a polished back and a polished final bevel.

[Mike Cherry]

Kevin, you've stumbled on to why micro bevels are so handy. Why polish an entire bevel when all you care about is the very edge. Somebody realized this and decided to slightly raise the angle so he only had a thin strip to polish.

[Kevin Perez]

Thanks, all. I thought I might have been missing something.

[Mike Cherry]

I'm certainly no expert Kevin, but it is questions such as this that keep me progressing in this craft. What I thought sharp was a couple years ago, isn't even close to what I think I know about sharp now. The willingness to try new methods is what opens my eyes more and more.

[Brian Holcombe]

Most of my primary bevels, on my western planes are left whatever they are when they leave the 140 Atoma plate. The major thing I've changed in recent times is to absolutely minimize the microbevel. That way it stays easy to change and easy to rehone. Once they get to the point where they're unruly then I work down the primary again with the 140 atoma.

The back need not be a mirror, but it must be flat near the last 1/4"~ and must be right up the cutting, if it is dubbed at all you will forever be resharpening and wondering why your blades remain dull.

[Mike Cherry]

Good point about the backs of the blade, Brian. I was fixated on creating mirror backs until I realized it's more about flat.

[Robert Engel]

Yes, its unnecessary.

Think about how the wood is coming off the plane iron.

I prefer to keep the back polished because I think you get a better edge when both sides of the bevel are honed to a polish.

This is what the advocates of the back bevel are talking about.

I, however, do not routinely back bevel my plane irons.

[Andrew Pitonyak]

Good point about the backs of the blade, Brian. I was fixated on creating mirror backs until I realized it's more about flat.

I just assume that when Brian posts I am about to learn something, generally agree, or smack my head and say "duh"... .In other words, a bunch of good information.

The point of a mirror finish is because then you know that it is very flat where you have the mirror because all the scratches are out. Well, I suppose that does depend on how you got that mirror. If I use a buffing machine, I might polish everything and still not have a flat surface.

I think that this is where David Charlesworth's "ruler trick" comes into play. A super tiny back bevel. David claims that this imposes a back bevel of approximately two thirds of one degree, on the blade.

If your stone is about 3" wide.... and the distance from the tip to the ruler is 2.75". And, if the ruler is 3/64" thick, then the angle is closer to 1 degree (because atan(3/64 / 2.75) = 0.9765 degrees). if your ruler is closer to 1/32, then you get the 2/3 value. math is your friend.

I finally used the ruler trick on a #7 plane that I was given. I spent more than 8 hours trying to flatten that blade. Sadly, I spent too much time on fine grits, but, I have never had a blade that badly out of whack. I documented the process with pictures and such, I just need to post it. There was a dip in the right side.... so, I finally just used the ruler trick.

[Brian Holcombe]

Thank you both!

The big indicator that I look for is to see if there is any light being reflected back at me at the extreme edge. If it does not show a bright line at the extreme edge and you are getting a wire edge building up on the reverse side then you are good. If it does reflect at the extreme edge then you are not finished and need to continue working. Don't be fooled by a wire edge on the reverse side if you are still seeing this line, you are not finished and should keep working. Next time I sharpen I will try and show this, it's difficult to photograph with a cell phone.

The biggest thing that has surprised me, when you grind at a low grit you build a very durable wire edge, this actually takes some time on the finish stone to remove, so watch for that.

Once the back is flat, for me it really only sees the finest and second to finest stone, unless I have to rework it for some reason. The finish should be uniform, if it is not then it is not flat. Since I use natural stones I'm looking for that nice haziness at the last bit of the edge, uniform all the way across.

It helps to keep the stones super flat, and minimize slurry build up (even with jnats). Naturals are nice in this instance, they're much less work to keep flat. With even my sigma or snow white stone I will lap them almost as soon as slurry actually builds.

The ruler trick is fine on western plane blades in my experience.