Intro: FLATTEN,SHARPEN, AND HONE YOUR CHISELS AND PLANE IRONS TO SURGICAL PRECISION!
We all know that dull tools are not only dangerous but leave an ugly trail of shoddy craftsmanship behind and just make for more time spent cleaning up their mistakes instead of hand crafting that perfect project you have in mind. With the help of this instructable, you can always make sure you have razor sharp tools at your side ready to chop, pare, plane, or shave even the gnarliest pieces of wood!
WHAT YOU'LL NEED:
- a sturdy FLAT surface (a hunk of marble, some plate glass, a few sheets of mdf laminated together, etc)
- varying grits of sandpaper (about 80-120 grit)
- a set of sharpening stones (you don't have to go super fancy here...ideally you want something close to 1000 grit, 4000 grit, and 8000 grit. you can also substitute a 6000 grit for the 4k/8k if that's the only available option.)
- a honing guide
- a ruler
- a marker/pencil
- tape or spray adhesive
- water (if you have water stones you're going to want a container to submerge them in and keep them wet during use)
- something to sharpen! most tools with a flat blade or iron will work
Step 1: LAPPING THE BACK FLAT
For this instructable, i'll be sharpening a plane iron from a no.3 smoothing plane. All of these techniques are applicable to just about any tool with a flat blade.
The first* and probably most important step in this process is making sure that the back of your cutting edge is dead flat and has a mirror polish. Take a strip of sandpaper and tape or glue it to your flat surface. Depending on the condition of your blade you may want start with a very course grit like 80 to really hog out some material. I went with 100 grit for mine.
Once the paper is secured to the flat surface, take a marker and fill in the first 1/2" or so of your blade. Then, lay that part onto the paper keeping all of your pressure on the sandpaper side. Take a few passes back and forth on the paper and check to see how much marker you've removed. This should give you a good indication of how flat your blade is. If you see some spots left, especially any that are up against the edge of the blade, keep sanding until all of the marker is gone and you have a smooth even scratch pattern.
It's also a good idea to soak your waterstones during this step to save some time.
*if your blade edge is severely nicked or damaged you may want to sand or grind down the angled part of the blade until you've removed the nicks. You can do this by setting up a grinding wheel or putting the blade in a honing guide at the proper angle and running it across your sandpaper. Just make sure to keep your metal cool while grinding it to prevent drawing out the temper. If it get's too hot or starts to turn blue you're going to have to remove that part of the metal- it will no longer hold a sharp edge. Once you've done this, THEN lap the back of the blade and follow the rest of the steps.
Step 2: POLISH THE BACK
Before you use your stones, make sure that they're flat, otherwise you'll be honing dips and valleys into your tools' edges. You can do this by drawing intersecting lines on your stone with a pencil and rubbing it against a flattening stone or diamond plate until they're all gone.
A few things to keep in mind:
- keep your stones wet-this helps create a slurry of iron and grit that actually does the sanding/polishing
- if you get a build up of metal bits (a black watery sludge), spray your stone clean and continue
- don't move on to a higher grit until you've COMPLETELY replaced the scratches from the previous stone with finer ones
- make sure to rinse the edge you're sharpening and the honing guide when switching stones so you don't mix grits
- always keep an eye on that last 1/8" behind the edge and make sure this stays flat on the stone at all times
Step 3: ONTO THE FRONT!
Now that the back is flat and polished, you can focus on the font edge of the tool. In these next few steps you'll be making a primary bevel on the edge, and then adding a secondary micro bevel. This is what will actually do the cutting, and this is what you hone every time your tool gets dull.
The first thing you want to do is determine the proper angle for your primary bevel. There are many different ways to figure this out and it all depends on the tool, the intended use, and your own personal preferences. A good all around angle is 25º. Most bench chisels, jack planes, and block planes will do well with this angle. Since i'm sharpening a plane iron from a smoothing plane, i'm not going to need as aggressive an angle because i don't want to remove a lot of material all at once. I want to take the thinnest possible shavings leaving a glass-like finish on the wood. I chose to give about a 22.5º primary bevel for a thinner, longer, and sharper edge.
Once you determine this angle you can set the tool up in the honing guide. Mine has reference measurements on the side so you know how far to project the blade out past the guide for the desired angle. Since i wanted something a little shallower than 25º i put the plane iron about 56 mm away from the front edge of the honing guide and tightened it up.
For future honing or resharpening it helps to write the distance needed to set your tool at the right angle directly onto the blade or tool itself.
Step 4: HONE THE PRIMARY BEVEL
With the tool or iron properly secured in the honing guide, you can now run it through your gambit of water stones. Now, keep in mind that if the primary bevel angle your grinding is different than what your tool already has, you don't need to regrind the entire front edge. you only need about a 1/16-1/8" strip along the front.
One very important part of this process is that you make sure you're honing all the way to the very tip of the tool! if not, you're leaving a dull cutting edge and just polishing the metal behind it. An easy way to make sure you're getting the entire edge is to check for a slight burr along the back edge of the tool. You may not be able to see it right away, but if you run your finger along the back you should feel a slighty jagged CONTINUOUS bump. If not, either keep honing or, if the edge is really far from where you're honing, leave the tool in the guide and go back to your sandpaper and marble setup for a more aggressive approach.
Again, continue honing on each stone until you've got a shiny polished primary bevel.
Step 5: TIME FOR THE MICRO BEVEL
After that you should have a tiny reflective sliver all the way along your edge. if you see this, then you are now the proud owner of a ridiculously sharp tool!
As soon as you're done sharpening you're gonna want to apply some machine oil or paste wax to anything metal to keep it from rusting (trust me, it will rust within minutes if you don't!)
Step 6: ADDING a CAMBER TO THE CORNERS
This is optional and not required for things like block planes, chisels, or spokeshaves. But for most smoothing planes people will round the corners a little bit to keep them from digging into the wood.
This step is very easy and only takes a few seconds. Take your tool or iron out of the honing guide, place one corner onto your highest grit stone and gently drag it across the stone about 5 times. repeat on the opposite corner. There's no need to put pressure on the corner, just let the weight of the metal do the work.
hope you enjoyed!