Posts Tagged ‘sharpening’
Sharpening hand saws is intimidating for most people, but there are some readily available options that simplify the process greatly. Here’s a quick overview:
Angles: Before sharpening, you need to determine the angles you want to file into the teeth of your saw. The rake angle is the angle between the face of a saw tooth and an imaginary line perpendicular to the baseline of the saw teeth seen when viewing a saw from the side. It is generally 12 to 15 degrees on a crosscut saw and 0 to 8 degrees on a rip saw. You also need to control the fleam angle, the angle that is filed across the face of the teeth, creating a knife edge that slices wood fibers when cutting. On crosscut saws fleam typically ranges from 15 to 25 degrees, rip saws typically have little to no fleam. (read Understanding Western Handsaws for more info)
Control: Once you know the angles you want to create, holding a file consistently and accurately for dozens of teeth in a row is tough. Fortunately, there are several options available to you that make saw sharpening fairly straightforward.
Option one is to make your own file guide. I picked this up from Ron Herman’s DVD and it works great. I made my guide out of some scrap cherry in about 15 minutes. The pictures will help explain the details, but the idea is to hold the file handle in your dominant hand and the file guide (with the tip of the file buried in it) in your off hand. Hold the file level and the edge of the file guide perpendicular to the saw plate. If you can do this, the guide will control the rake and fleam angles for you, it’s easier than it sounds. (You may notice my guide is using a 30 deg rake and fleam angle, this is fairly steep for both but it was deliberate for this saw. You typically want something closer to the angles listed above.)
So this guide works well in a pinch, but if you have several saws to sharpen you’ll quickly realize you need a new file guide for every angle combination you want… this may only mean making 2 or 3 guides, but for others it would mean making many more. So for all your file guiding needs there are a couple adjustable file guides you can purchase. A reasonably priced option was recently released from Veritas and functions along the same principles as the wooden block, but you’ll notice a variety of angle combinations and file sizes can be accommodated with this single device. A second option from Blackburn Tools gives you the same functionality, but in a much classier package and at a premium price.
I have not purchased a file guide from Veritas or Blackburn so far, but I have more sharpening on the horizon so I intend to shortly. Hopefully this gives you the confidence to pick up a saw (preferably a cheap one that you won’t mind practicing on) and get sharpening. It’s really very simple and Ron’s DVD, as well as various free videos from youtube and Lie-Nielsen, will provide you with all the information you need.
Sharpening is arguably the most essential part of working wood with hand tools and one of the most intimidating. If your tools don’t seem to “work right” they are probably dull. Chisels, saws, hand planes, anything that cuts wood really, will function better and better the sharper they are (though there is a point of diminishing returns with sharpening). Most guides to sharpening start at the beginning (grinding a profile, lapping the back, etc.) and carry the process through to a finished tool. This feels (and can be) very time consuming. The reality is once a tool is prepped, sharpening takes minutes and is very simple. Only repairing a damaged tool, like a dropped chisel, will ever take more than a few minutes once that tool is up and running.
Here’s what sharpening usually looks like in my shop. I pull out my little bin of accessories (pictured below) and get set up. This involves flattening my waterstones (for more info click here) and setting up my honing guide. My honing guide has a straight roller as well as a cambered roller, so depending on the tool I’m sharpening I may have to swap rollers. Then I set the angle, clamp down on the tool, and I’m ready to go.
One quick tip, if you’re only planning to re-hone an edge on your finest stone you can just jump into it, but if you need to start on something course (less than 8,000 grit) the stone typically needs to soak for a few minutes. I generally put my stones in a plastic bin to start soaking, then get my tool set up in the jig. Usually by the time the tool is set up the stone is almost ready to go.
Another thing that can help beginners or if you’re sharpening a tool you’ve never sharpened before is to blacken the cutting edge with a permanent marker. Take a couple strokes on your stone and check where the marker has been removed. This gives a clear and early indication of any problems that may be arising. If you know the blade is square, for instance, but you’re removing marker from the corner of the cutting edge, then your blade is either mounted at a skewed angle in the jig or you’re putting too much pressure on one side of the tool. Regardless, the sooner you catch it, the easier it will be to correct it. If the cutting edge isn’t square to begin with, the marker helps to indicate when you’ve removed material all the way across the cutting edge, re-establishing the desired square edge.
Up to this point, I’ve burned about 5-10 minutes of my time getting everything out, soaking the stones, and getting the tool set up. Before I begin to actually sharpen, I check my guide’s cam position. The Veritas guide I use has its roller wheel mounted on a cam which makes sharpening micro-bevels fast and easy, but only as long as you remember to start the roller on the lowest cam setting.
So with the tool mounted, the cam set in the low position, and the stone soaked, I take a few swipes on my 4,000 grit stone (usually, occasionally I go back to 1,000 if I have more material to remove). I check to make sure I’ve sharpened all the way to the tip, then rotate the cam wheel to raise the tool and hit my 8,000 grit stone. When the bevel is polished, I carefully remove the tool, polish the burr off the back of the tool and wipe it down with oil. Done. This should only take 2-3 minutes. I could stop here, but because I’ve taken the time to get everything out and prep the stones, I typically try to capitalize on my effort by finding 4-5 tools that might be getting dull. I hit each one and clean up. When all is said and done, I’ve spent 20-30 minutes sharpening, start to finish, but I’m left with several razor-sharp tools and when you’re using quality tool steels the edge lasts a long time.
So don’t let sharpening intimidate you, it’s fairly simple and absolutely necessary. For more information, you can check out the course material I developed for a sharpening class I’ve taught. Sharpening Handtools
One thing I struggled with when learning to sharpen hand tools was creating the proper geometry. Whether I was flattening a chisel back or cambering a plane iron, the results were always unpredictable. Eventually I caught onto the fact that my stones were not as flat as I thought they were… but why not? I was flattening them with a flattening stone after all, shouldn’t they be flat? Isn’t that why it’s called a “flattening” stone?
My problem was the flattening stone itself was not flat. This created non-flat waterstones which resulted if poor tool geometry. I am making the distinction about the geometry because I think it’s important. I was getting a perfectly acceptable polish on the tool, but not always where I was expecting it. Poor honing (or polishing) requires a finer sharpening media, inaccurate or inconsistent honing requires a flatter sharpening media.
So down to business. I strongly recommend avoiding the Norton Flattening Stone. It’s inexpensive and might work at first (though don’t count on it), but it quickly goes out of flat and will do more harm than good. “But can’t you just re-flatten the flattening stone?” you might ask… sure, if you want to burn through a lot of sandpaper on a regular basis, waste time, and always wonder if it’s time to re-flatten the flattening stone. I’ve also heard other woodworkers and even a student of mine complain about this product, so save yourself the hassle and try one of the alternative methods I talk about below.
Don’t misunderstand me. I’m not bashing Norton. I use their waterstones and use several other products they manufacture. This stone is just not one of them. So if you’re struggling with something as simple as lapping a chisel, your stones may not be flat. Here are some things I would suggest you try:
-Lap your stones on sandpaper laid over a flat surface such as granite. This is not my favorite, it’s expensive and messy, but in a pinch it works well.
-Buy a reliable lapping plate. There are several and the are pricey. I own the DMT Dia-Flat Lapping Plate and it can cost up to $195. Shapton also makes a lapping plate that runs around $400. Others use course diamond stones to lap their waterstones. As long as the lapping stone stays flat it should work.
-Use stones to flatten stones. I know a few people who do this (though I’ve never tried it) and they have no complaints. If you’re on a budget, give this a shot… it’s essentially free. The typical process would be to buy a combination stone, such as a 1000/4000 grit stone, buy a purely course (1000 grit) stone, and a purely fine (8000+ grit) stone. Use the course side of the combination stone to flatten the purely course stone. Then use that stone to flatten the 4000 grit side of the combination stone, then use the 4000 grit stone to flatten the 8000 grit stone.
-I know some people lap on a cinder block… that’s actually not a terrible idea except you can’t rinse it clean very easily and I would think it could be ground hollow, especially with course stones, fairly quickly. I would avoid this method personally, but I can’t say it won’t work for you, at least temporarily.
A few more tips for flattening your waterstones: -Rinse your lapping plate between grits to avoid embedding courser grit on finer stones. -Chamfer the corners of your stones. If you leave them sharp they will eventually chip out. This can be done right on the lapping stone. If you’re using the stones to flatten each other, you can’t do this so chamfer the stones on something else like a cinder block… or hey, go buy the inexpensive Norton flattening stone and use it solely to chamfer your stone’s corners… at least that’s one thing it would be useful for.
Keep it sharp. -WMT