Double Bevel

[woodbloke]

Having read this months F&C there was a very interesting article by MrC on honing a very slight bevel on the flat side of a plane blade to make a double bevel, suitable for planing interlocked exotics. He mentions a standard angle of 30deg as normal and then an additional angle of 25 deg on the flat (about .3mm wide) giving a combined angle of 55 deg, which can be progressively increased depending on the timber being tackled, he also mentions that this technique is better suited to standard planes rather than low angle BU ones. Has anyone tried this.....might be worth a little bit of experimentation - Rob

 

[Derek Cohen (Perth Oz)]

Rob

What you are describing is referred to as a "Back bevel". This has been an established practice for a long time, one that predates all of us here.

It is best suited for BD blade configurations (with BU planes a backbevel reduces the clearance angle), especially those with a lower-than-desired bed angle. A Stanley plane has a 45 degree bed/frog, which is the cutting angle regardless of the angle of the bevel. Say the bevel angle is 30 degrees, then the cutting angle remains the 45 degrees of the frog. Now add a 10 degree back bevel and you increased the angle of attack by 10 degrees, so the plane is now cutting at 55 degrees.

Adding a 25 degree back bevel is unusual (very high for a Stanley) but I know that DC has spoken of using 70 degree cutting angles on very difficult grain.

Regards from Perth

Derek

 

[dunbarhamlin]

If clearance angle (between the trailing face of the blade and the stock surface) is significant, presumably a plane with a higher angle frog will perform differently to one with a standard frog and a back bevel?

And by the same token, LA and standard block planes with bevels ground to give the same working angle will also perform differently.

Is there an optimum clearance angle? I thought (but expect I'm wrong) that just shy of flat to the surface would give maximum edge resilience and blade stiffness without compromising performace.

Cheers
Steve

 

[Paul Chapman]

Rob, not tried it myself, but presumably it would give a similar result to the York pitch frog, which Lie Nielsen sell for their bench planes, which converts the blade angle from 45 degrees to 50 degrees http://www.lie-nielsen.com/catalog.php?grp=1246

Cheers :wink:

Paul

 

[Derek Cohen (Perth Oz)]

Steve

On BU planes, the clearance angle is (as I understand) 7 degrees. Therefore, a plane with a 12 degree bed will manage a 5 degree backbevel. To be frank, there is only one reason I can imagine for a backbevel on a BU plane. This is to strengthen the blade's edge.

The other issue is that there is a difference between BU and BD planes in regard of the bed angle. The lower angle of the BD planes translates into a lower centre of gravity and less effort in driving the plane forward (cutting angles held equal). However, BU planes do tend to wear the underside of the blade more quickly than with BD blades, which translates into less blade life. Pros and cons.

Regards from Perth

Derek

 

[Alf]

Gosh, it's simply ages since we had debates about back bevels - pesky bevel up planes upset the natural cycles of plane discussion. :roll: :lol:

BBU (Before Bevel Up) I did indeed play about with back bevels and they work very well. Very handy in getting some use out of an iron that may otherwise be pitted beyond help, but that's by the by. Bit of an extra fiddle having to hone another bevel mind you, but certainly something well worth having in the arsenal. Spookily my very first post under this nom de plume was on the subject - and I made the classic ruler-trick-back-bevel-confusion mistake which is Not Allowed.

Cheers, Alf

 

[Philly]

Rob
I did some experimenting with BB's . They work great!
Here's the link....
Hope this helps
Phil

 

[woodbloke]

First time I've come across this sort of trick so I just wondered if anyone else had had a play around with it. MrC was using an an 'effective pitch' (the sum of both bevels) of about 80deg for planing some difficult timbers ie lignum vitae - Rob

 

[dunbarhamlin]

Thank you Derek et al - was blurring edge resistance to damage and dulling, which are inversely related.

Cheers
Steve

 

[Paul Chapman]

edge resistance to damage and dulling

I've found that honing a plane blade for maximum resistance to damage and dulling can sometimes be useful. Since the 1970s, when I used a lot of Formica, I keep one blade for my old Stanley 60.5 block plane (bevel up) honed to a very steep angle (don't know what the angle is but the projection from an Eclipse honing guide is about 7/8"). I use this for planing any types of plastic (Formica, perspex, Contiplas edging strip, etc). Can keep planing for several times longer before the edge breaks down. Nothing to do with back bevels, but might be useful to someone.

Cheers :wink:

Paul