Sharpening Block plane blades

[Geoff Harris]

I have a question about sharpening a bevel up plane blade and David Charlesworth's "ruler trick" method of putting a back bevel on plane blades.

I've started using the ruler trick on by bench planes and it works great for shortening the time it takes to polish the back. However I wonder if it is appropriate to use this technique on a block plane blade?

Geoff

[Ken Werner]

Putting a back bevel on a bevel up block plane would be similar to putting it on a chisel - not helpful. It would reduce the support the blade gets from the plane, and could increase chatter. Anyway, that's this fettler's .02.

Ken

[Hans Braul]

I asked the same question a while back and was convinced it was not a good idea. Here is the link (I'm not sure this will work):

http://www.sawmillcreek.org/showthread.php?t=43756

Regards
Hans

[Eddie Darby]

Does anyone here golf? If so, then you have probably hit a few sandtraps. The trick to getting out of a sandtrap is to have a negative "Clearance Angle". The opposite of digging in or positive "Clearance Angle", which is what you want in woodworking.

Imagine the leading edge of the sand wedge to be the leading edge of your blade, and the "bounce" or trailing edge of your sand-wedge to be the place on the blade where the bevel ends.

In golf you don't want to dig into the sand, so you open the face of the club up so that the "bounce" is now the lowest point, and hits the sand first, causing the club to bounce off the sand. Usually the amount of built-in "bounce" in a sand-wedge is 15 degrees.

As long as your block plane blade is not "bouncing" you will get the job done. The "Ruler Trick" put so little angle on a blade that you will not even notice it. On my Norton stones that are 3" wide and with a ruler that is 1/32" thick, I get around a 0.7 degrees of angle of reduction in the "Clearance Angle". I would say that if we noticed such small angles, then we would be talking about 1/10th of a degree changes all the time.

I would save myself the work and go ahead with the "Ruler Trick".....and stay out of the sandtraps!

If you want to dig in with a gouge, try removing the "bounce" by rounding the area where the bevel ends at the blade.

[Mark Singer]

If the plade is in good shape, it is pretty easy to flat sharpen the back. If it is pitted or warped...the ruler trick saves a lot of time.

[jonathan snyder]

Hi Folks,

Can you enlighten me? I'm not familiar with the ruler trick. Do I understand correctly that it is used to flatten the back of a plane blade?

Thanks
Jonathan

[Mike Henderson]

Hi Folks,

Can you enlighten me? I'm not familiar with the ruler trick. Do I understand correctly that it is used to flatten the back of a plane blade?

Thanks
Jonathan

I think this is the same as the "ruler trick". It's something I, and a lot of other people, do on old, pitted plane blades.

Sometimes when you purchase an old plane, the blade is rusted and quite pitted. These pits can be on the back face of the blade - especially on the cutting edge arris. Normally, you would flatten the back of the blade to take out all the pits and high and low spots. However, when there are serious pits on the back, it's pretty tough to grind that whole back surface down enough to get rid of the pits. And many old plane blades are laminated so you're grinding away the hard, working steel and making the blade thinner.

To avoid this, you can "flatten" the back of the blade at an angle. How do you flatten at an angle you may ask? What most people do is to raise the back of the blade a small amount (the thickness of a metal ruler is about right) so that the blade is actually at an angle on the stone. The angle is quite small, maybe only a degree or less. This allows you to grind down the back of the blade at the cutting edge arris - in much the same way you would put a back bevel on the blade - and grind out those pits only at the cutting edge arris.

The disadvantage of this approach is that you change the cutting angle on a bevel down plane and reduce the clearance angle on a bevel up plane. The amount of change is quite small and is usually not noticable - and it allows you to use a blade that would be extremely difficult to flatten in the normal manner.

Mike

[jonathan snyder]

Thanks Mike,

I'm always learning something new from you guys!

Jonathan

[Derek Cohen]

Geoff

Go ahead and use the "Ruler Trick". It works well and it makes it easier to remove the wire edge at the conclusion of honing. That is why I do it, not just as a shortcut to a flat blade back.

To emphasise, I use it on all my bevel up blades. This is perfectly safe. The Ruler Trick will create a micro back bevel of about 0.5 degree. The bed of a low angle block plane (and low angle bevel up smoother) is 12 degrees. You need about 7 degrees clearance. A one-half degree is meaningless in this context.

Regards from Perth

Derek

[Ken Werner]

Derek,

I sit, corrected. Thanks for your comments.

Ken

[Geoff Harris]

I was in the middle of sharpening a set of blades when I realised I didn't have a clue if the technique worked for blades for bevel up planes. I reread the article I had on it and it just didn't mention anything about this. So, I'm really glad to have a resource like Sawmill Creek to turn to!

Thanks to everyone who replied!

Geoff.