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Sharpening

And now... the blade


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     If you have a new plane you'll have a blade (also called an iron) that looks something like the one on the left  whether it's the original or a replacement Hock blade.  (Hock is recommended by almost everyone.)  It'll have a straight edge, and a 30 angle on the blade.

    But if your plane is second hand the chances are it's blade (iron) will look something like the blade on the right.  Rust and pitting can be a big problem.   If the former owner tried to plane a piece of wood that had a nail, or even a stubborn knot in, you'll have an even bigger problem  .
The cutting edge may even have been beveled or the plane's angle may have been changed.  Forget about finding both flat and smooth.

Even if you've replace the old one you'll have to sharpen your iron.  You may or may not have to grind the blade.  We'll get to the Scary Sharp system in a bit, but for now let's look at the steps you go through if you have a used blade.  It'll include all the steps.  If you want to get to the actual sharpening, then jump on down. 

  First, take the blade out of the plane and examine it.  You're really interested in the forward 1 or 2 inches.   Look for nicks, rust and pits along both the edge and the back.   Both have to be flat and smooth for the plane to work at it's peak.  If the blade is generally rusted you can clean it with a steel brush and a lot of light oil.  Just get the rust off.  If you're using a brush in an electric hand drill or a bench grinder, be careful not to over heat the blade.  After you've got it clean, dry it off and put a light coat of candle wax over the area you're not going to sharpen.  This will prevent that area from rusting again.  (According to several people wax is one of the best moisture blocks.  You can use paraffin, sold at many grocery stores.  I use the stubs of old candles.)

What about blade angle?

There's always been a hot debate among rod builders about the best blade angel for bamboo.  Both  9 and 60  Stanleys come with the blades ground to 30.   Most people agree the the angle to bamboo of the 60 (12 body angle and 30 blade angle is too shallow and will cause the bamboo fibers to tear.  The answer to this, according to those that use 60s, such as Ray Gould,  it to grind the edge to a steeper angle. 

Other builders such as Jack Howell recommends grinding a new angle on the 9.  Yet, other builders, such as Wayne Cattanach say no.  Australian rod builder, Tony Young says keep the 30 angle on the blade but make the plane angle steeper.   In other words, it's up for debate.  You can experiment and see what works best for you

A blade angle story
One of the blades in a used plane I own refused to take a really sharp edge.  I went through the steps I'll outline below several times and didn't get even close to what I'd call sharp.  The original angle was the standard 30.  I decided that, because I wasn't going to be able to use the blade as it was, I'd try a different angle.  I ground and then sharpened the blade to 40.  The difference was dramatic!
I have no explanation why this change in angle made the blade sharpen better, but there's no doubt in my mine it did.
Grinding blades to an angle.
Why grind a plane iron?  Many used irons may have nicks in them, or they may not be ground flat.  Most new blades come pre ground to 30.  You may want to change the angle to your own taste.  Your aim is to remove any imperfections, get the cutting edged square and at a cutting angle you want.

So!  Time to warm up the grinder!  Not so fast.  There are a couple of  questions you need to answer first.  What angle are you going to grind and how do you set that angle on your grinding tool.

If you have several planes, you can experiment.  Try grinding one blade to 30 and another to 40.  Try one at 45 or even 50.   Remember that different planes may like different angles.   If you do have different planes, I'd recommend writing the angle you sharpened on the bottom of the blade.  That way you'll know. 

I started out free handing my first plane irons.  I'd get close then sharpen them to the angle I wanted.  It worked but it took a lot of extra work.  It wasn't a very good feeling to know that I was guessing about something like that.  After thinking about it for several months, I came up with the following.

The grinder should have some form of rest for the blade. The other end rests gently on the wheel.  The angle the blade touches the surface of the grinder is the angle you'll end up with.  If you move the blade across the rest toward the wheel, the angle you grind will decrease.  If you pull the blade back across the rest,  the angle will increase.  If you're having problems visualizing this, go try it on your grinder.

One point on the outside of the wheel is the same as all the other points, so the question is, where should the the blade touch the wheel.   To solve the problem I went back to high school math.  If you look at the diagram to the right, you'll see what I'm talking about.  The only thing I can measure is the angle between the blade and the center of the spinning wheel.   I know that if line X just touches the edge of the wheel and is 90 to line Y then adding 90 to my grinding angle will give me the angle I want.

All I had to do was measure it.   I did that with a simple gauge made from a piece of cardboard stock.  I placed one arm of the gauge on top of the blade and moved the blade in or out until the other arm of the gauge crossed the axis of the grind wheel and I had my angle.

If the desired angle is 45 then add 90 and 45 for a total 135.  I create that a gauge from card stock with that angel on it.


Now let's turn on the grinder.  I want to make sure I'm grinding a straight face that's square side to side.  My grinder is a drill held upside down on a base, with a wire guide.  To keep everything from moving around I made this grinding jig.  It was simple to build.  All I had to do was make sure everything was square.   I hold the blade in place with a small C clamp.
My grinding jig.
Make light passes over the Wheel.  Don't stop until the blade clears the wheel.  Don't go to slow.  Heat is an enemy.  don't  let your blade get to hot.  If it starts to get hot let it cool off before continuing.   Check your progress often.  After you've completd grinding take the blade out of the jig and use a square to check the blade is true to the iron.   You only have to do this once, so take your time.

And now... Sharpening.
Your objective is to get the bottom inch of the back of the blade as flat and smooth as the edge of the blade on the other side.  The flatter they are, the sharper the blade where they both meet.  That's what sharp is.

There's not a lot to be said about sharpening that hasn't already been said.   There are two basic schools of thought on how to get a plane blade really sharp.  The first uses Japanese water stones.  Both Wyane Cattanach and Jack Howard recommend this form of sharpening in their books.  The other school is suggested by the maker of "Hock" blades it's often called the "Scary Sharp" method of sharpening.

I use the later for two reasons.  First I already had everything I needed and second I wanted to get to work right away, and didn't want to wait for japanese water stones to be shipped.  I'd just finished polishing the sole of my first block plane. I started wondering if I could make it flat and smooth, why I couldn't do the same with a plane blade.   As it turns out I can. (It was several months later that I learned I wasn't unique. )

To do any kind of sharpening, you'll need two tools, a sharpening jig and a stop block.  You can buy several types of sharpening jigs or you can build your own.  I recommend you use one.  So does everyone I know who sharpens plane blades.  I could never come close to being able to really sharpen a blade without this simple tool.  Which ever one you chose, make sure the back of the blade can be flattened without remvoing the blade from the jig.

The stop block is easily made with a piece of scrap wood.  All it has to do is allow you to set the blade angle in your jig to a predetermined setting.

My sharpening jig

My sharpening jig and stop block 

The rest is simple.  Put a fairly course piece of  wet and dry sandpaper on a flat surface.  (Make sure it can't move around)  Move your blade backward and forwards or in a figure 8 pattern over the course material until you get a uniform surface.  Now feel the back of your edge.  You should feel a wire bead has formed along the back.  This bead will have to come off, so turn the blade over and put the first inch flat on the sandpaper.  Move it in a circuler motion.  This should remove the bead.

Once you've done this move to a finer grade of sandpaper and repeat.   Once you've gone to the finest you have,  you can polish the blade.  Place a strip of 2 in. masking tape on a flat surface, cover it with a light coat of polishing compound and move the blade over the surface the same way you were moving it on the sandpaper.   Don't forget to turn it over and polish the back of the blade.

You can lightly move you thumb across the edge but if your plane is really sharp you run the risk of cutting yourself.   A better way is to lightly press the edge on your thumb nail and see if the blade digs in or skids across the top of the nail.  A sharp blade will dig in.  You can try to shave your arm, if you're into that.  (I've got to admit, I've done that from time to time.)  Or you can hold the blade up and look directly at the edge.  If you see any light glinting off the edge, the blade isn't as sharp as it should be.  If it looks gray, you've done your job.

A little paraffin will keep the moisture out while the blade's in storage.

Re-sharpening

From time to time the blade will go dull.  don't try to use it to build rods until you've sharpened it again.
I usually sharpen from about 400 grit on up.  It should go fairly quickly.  don't forget to polish and don't forget the back.  It's just as important as the edge.

I try never to put a plane away without sharpening the blade and covering it with rust prevention.


How about the plane sole?
 

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