Back Bevel on Bevel Up Planes?

[Hans Braul]

Is it a good idea to hone a back bevel on BU plane irons? It won't affect the cutting angle but I would think it could improve the durability of the edge, especially on a blade ground to 25 degrees, without affecting performance. Just wondering.

Hans

[Jerry Palmer]

A back bevel could be detrimental in that it could interfere with the clearence angle beneath the cutting edge, especially on a low angle bevel up plane.

[Phil Hirz]

Hans,

It should be okay to put a back bevel on bevel up planes as long as you keep the bevel angle small and hone only a microbevel. I would not put a back bevel any larger than 5 degrees on a bevel up plane. If you do then you will start to affect performance just like Jerry said. Also, I would only hone a very slight back bevel on your highest grit stone.

Dpending on how you use your tools it might not be worth it to hone a back bevel. I found it kind of annoying to hone a 5 degree back bevel. When I sharpened a back bevel on one of my planes I placed a 1/32" thick ruler on my 8000 grit stone and then projected the blade out roughly 3/8" and then honed back and forth. It was kind of tedious. Try it out and see if it works for you. Worst case scenario you will just have to grind back your blade a little bit to get rid of the back bevel.

-Phil

[Mark Sweigart]

A back bevel on a bevel-up plane will result in a dull edge at a much quicker rate.

You can read more about it here: http://www.traditionaltools.us/cms/index.php?name=Forums&file=viewtopic&t=153

[Jerry Palmer]

That is an excellent thread over there. One of the things it brought to light for me when I saw it some time back was the fact that both the bevel and the back of blades sustain wear as well as the actual edge. I had noticed that at times I had to raise the back of a blade off of the polishing stone in order to remove the wire edge raised from honing the bevel but it never dawned on me that it was caused by wear to the back of the blade. So when ever I find that to be the case now, I go back to a courser stone and reform the bevel with emphasis on moving the edge back sufficiently to get back to a flat back.

[Jake Darvall]

It could be detremental. But a small one wouldn't hurt I'd say. like 2 degrees ....probably could put 5 degrees on and it wouldn't hurt, as long as you don't skew the plane too much, since skewing the plane drops the clearence angle as well.

The only reason I'd ever consider it, is to speed up the sharpening process, or to hone past any rust pits right on the back tip of your blade.

[Hans Braul]

Great response - thanks to all. I think I'll stick with no back bevel. I was just thinking it might speed up the sharpening process if I just took a quick swipe on a fine stone on the back of the blade, when a touch-up was required. Maybe I'll experiment a bit, but the article was excellent.

Thanks
Hans

[Phil Hirz]

That was a very interesting article. It really went into detail concerning the different factors that lead to the dulling of an edge.

It left me with one question nagging at my mind though. Typically the most widely accepted and discussed method for controlling edge durability is the bevel angle. A larger bevel angle results in a stouter edge and longer edge retention. In a bevel down plane at what point does the increase in bevel angle, cause a detrimental effect on edge retention due to clearance angle?

For example: There are many people that like to hone their bevel down plane blades at angles up to 35 degrees. This would result in a clearance angle of 10 degrees with a 45 degree frog. Would it actually be better to hone a bevel angle of 30 degrees and increase your clearance angle to 15 degrees?

Phil

[Frank Desaulniers]

Just a few thoughts to add to the discussion...



It left me with one question nagging at my mind though. Typically the most widely accepted and discussed method for controlling edge durability is the bevel angle. A larger bevel angle results in a stouter edge and longer edge retention.

The optimum bevel angle for maximum edge retention depends on the type of steel. Below the optimum bevel angle, the edge fails (crumbles, chips, or rolls over). Above the optimum angle, the blade loses it's sharpness more quickly (the edge stops cutting efficiently after only a little planing; because the bevel is too "fat" it only takes minimal removel of metal to stop the blade from slicing). IIRC Steve Eliot mentioned around 25° optimum for O1 and around 30° (or just a little more) for A2. You'll have to check his site for the precise angles (sorry).


In a bevel down plane at what point does the increase in bevel angle, cause a detrimental effect on edge retention due to clearance angle?

For example: There are many people that like to hone their bevel down plane blades at angles up to 35 degrees. This would result in a clearance angle of 10 degrees with a 45 degree frog. Would it actually be better to hone a bevel angle of 30 degrees and increase your clearance angle to 15 degrees?
Phil

Actually it's not (only) edge retention that is lost but clearance...as the angle increases clearance diminishes on bevel-down. Common knowledge (whatever that is, but I'veread this all over the place) says to keep a clearance angle of at least ten degrees. I notice the my low-angle bevel-up planes start skipping (stop biting) noticeably sooner than my bevel-down planes even if, if I take the microbevel into account, they have similar clearance angles (12°). Makes no sense to me but I have constantly noticed a difference, my BU planes just quit sooner. However, my 20° block plane that I use as a little smoother last longer. I think that 19th century miters were made at 20° for a reason (IIRC Wiley mentioned that in the thread on TT). I'm soon going to explore this avenue (20° BU smoothers).

[Frank Desaulniers]

Great response - thanks to all. I think I'll stick with no back bevel. I was just thinking it might speed up the sharpening process if I just took a quick swipe on a fine stone on the back of the blade, when a touch-up was required. Maybe I'll experiment a bit, but the article was excellent.

Thanks
Hans

If you want to do the ruler trick it doesn't make much of a difference. It works out to less than one degree (the ruler trick is not really a back bevel). I don't use the ruler trick but know a few people who do on BU planes. I'd feel like I'm losing control of my sharpening because I'd need the ruler every time I sharpen (I misplace my tape measure and pencils very often).

[Eddie Darby]

The woodworking channel has a show on by David Charlesworth, that will show the "ruler trick".

http://www.thewoodworkingchannel.com/

10/5/2006 11:00 PM Woodworking At HomeIssue #7 - How to Sharpen Tools

10/5/2006 11:37 PM Lie-Nielsen Toolworks - Plane SharpeningKeeping Waterstones Flat

10/5/2006 11:49 PM Lie-Nielsen Toolworks - Plane SharpeningThe Ruler Trick

Eastern Time!!!!

I can't get the schedule for Friday,but they usually show it 3 or 4 times in a 24 hour period of time.