The biggest sharpening mistake woodworkers make (And why...)

hi I'm James Hamilton from stuffing ups woodworking Journal and this is the biggest sharpening mistake a lot of woodworkers make so you've read a bunch of articles you've watched all the YouTube videos you spent hours with your sand paper your water stones or whatever you use and you just can't figure out why your tools don't make those wispy thin shavings that everyone else seems to be getting the problem may be simple your tools aren't sharp I know you've spent a lot of time and they feel sharp it may not be that you haven't spent enough time on the bevels or that you're not using fine enough grit the problem could be that you're not paying proper attention to the back of the tool many woodworkers think that the shinier the bevel of the tool the sharper it will be but the bevel doesn't do the cutting the cutting is done where the bevel meets the back at that intersection where two planes come together that's what matters if you never pay attention to the back of your tool you only do it half of the job does that mean you have to double your sharpening time spending as much time on the back as you've been doing on the front nope because a little time spent on the back will also reduce the amount of time you spend on the front you won't be wearing away your bevels wondering why your tool is not sharp enough instead you'll be doing your woodworking first though it's important to understand why the back must be flat remember I said the cutting edge occurs right at the edge where the two planes meet it's easy enough to understand with this little side profile drawing but a chisel is a three dimensional object if you take a head-on view the potential problems come into focus if the back of the chisel has a concave or hollow surface then parts of the edge will be sharp and in contact with the wood when you use it but not other parts likewise if the back is bellied or convex then that portion of the edge will be able to cut wood but the rest won't so the back of the tool is just as important as the bevel tool makers have understood this for as long as there have been tools and it used to affect the way they made them when a piece of tool steel is heat treated it almost always warps one side ends up belied and the other side hollow in the old days a Western tool maker would wait to grind his bevel until after it was heat treated then he would take a look at that piece of steel he would find the bellied side and that is where he would grind his level so that the back side would be the hollow one Japanese toolmakers would take it a step further they would intentionally Forge a deep Hollow in the back side of their chisels and hand plain irons but wait a minute if a hollow back is a bad thing why would tool makers do it intentionally because they know the heat treating process is going to warp the tool and the only way to get it flat again would be to grind it and polish it in modern times they've shifted that responsibility to you along with a little bit of cost savings but if you're gonna save a few bucks by flattening the back yourself you'd better hope that your manufacturer gave you one that has a hollow back instead of a belly because the more belly there is on the back the more steel has to be removed to get it flat now let's look at a real world example if you took a new chisel and you rub it on a stone you'll quickly see what you're dealing with the high parts of the steel will be shiny the low parts will be dull or vice versa depending how the lights hitting it to get it flat you're gonna have to wear away all those shiny areas and tell the dull areas come in contact with the stone too and they become shiny this can be a bit of a crapshoot with many tools one chisel in a set may require just a little bit of work it might be mostly flat right out of the package while another tool and that exact same set may require a ton of work the most difficult chisels are those that have a full bellied back you know how hard it is to get rid of a belly and what the tool that means a lot of Steel removal to get rid of what amounts to a hump in the center those cases are more common these days sadly because manufacturers are grinding their bevels before the heat treating process when the steel is softer and easier for them to work when they finally get around to heat treating it and it inevitably warps well now you've got a 50% chance that that belly is gonna end up on the back where you've got to deal with it instead of on the front where it really doesn't matter only the finest chisels are flat enough for use right out of the package even though most manufacturers do try to grind it flat a little bit these family sweetheart chisels which I really like weren't flat when they were new I had to do a fair amount of work to get them there but you'll notice that I didn't flatten the entire back you can even see the grinder marks left by the manufacturer on most of it and what I did work it they aren't perfectly smooth and shiny it might look so on camera but there's some scratches in there this leads us to two important questions first does the back have to be perfectly shiny and polished like a mirror as well as flat and second how much of the back has to be flat let's start with the shiny part the whole point of polishing is to remove the deep scratches that create a serrated edge because a serrated or toothed the edge won't cut as well it won't leave as fine a surface behind and it won't last as long between sharpening it doesn't matter if those scratches are on the front beveled side or on the back if they touch the edge where those two planes meet at the intersection the effects gonna be the same if those scratches are really shallow really fine then the effects gonna be minimal it's fine if one or two deep scratches are there but not a ton of them that's not a big deal either as long as they aren't so deep that they're leaving grooves or ridges in your workpiece as you work though with the tool but a lot of deep scratches left behind by a coarse stone that's a bad thing there's a reason people shave with a razor and not a bread knife how course is too coarse is the subject for another video which you already made I'll put a link to in the notes below this one my point is your edge is only as fine as the coarsest of the two planes that make it up if you get perfectly polished on your bevel but you got tons of deep scratches on your back well you waste your time on your bevel now if the important part of the edge is the point where the two planes meet does the rest of the toll really matter do I have to flatten the entire back or just the part right next to the edge technically you only have to flatten sharpen and polish the thin strip of Steel on either side of that intersection one on each plane the rest of the back or even the rest of the bevel for that matter has no effect on sharpness and that little tidbit of information is what makes the ruler trick possible the ruler trick is a way to flatten the back of a hand plane iron in seconds instead of hours I'm not sure if it was practice much in the old timey days but modern woodworkers credit David Charles worth with its development it's pretty simple instead of wearing down the entire back of this plain iron which might have a great big belly on it and so it could take ages to get it all flat why not place a thin metal ruler on a stone and use it to lift the plain iron at a very slight angle so that the work is concentrated on the very edge where it counts the effect is an almost imperceptible back bevel it looks shiny to the eye but it's actually a slight bevel and that creates a new perfectly flat plane although a very narrow one to intersect with the bevel on the front it works try if you need a ruler I'll link to a couple inexpensive ones in the notes below but really anything about 1/32 of an inch thick will work just fine there are two downsides to a ruler trick though first you have to repeat it every time or two you sharpen your plane iron as your edge dulls and rounds over and then you go back to your stone or whatever and you sharpen it you are slightly shortening the tool it doesn't take much time before you've removed that fine back beveled portion so you have to get your ruler back out and restore it really you're flattening the back but you're doing it incrementally one thin strip at a time every time or two you sharpen and that ends up being a lot less tedious than sitting for an hour or more in flattening the entire back of a bellied or badly hollowed plain iron the second downside to the ruler trick and perhaps its most significant is you cannot use it with chisels well you can if you want I do some of my chisels with back bevels because I don't want to flatten them but that back bevel limits the functionality of the tool I can still chop with it I can even do some trimming if I hold it at an angle but I can't do anything with my chisel that requires using the back as a reference such as paring one surface flush with another or using a guide block to keep the chisel perpendicular when paring dovetails in cases like that the back of the chisel may look like it's fully in contact with the wood but that fine back bevel lifts the cutting edge slightly up and it's not gonna cut since many new woodworkers only have one set of chisels they use for everything then I'd say don't use the ruler trick at all if you're going to use it use it only on chisels that you're going to be chopping with not ones that you're going to be pairing with in those cases you're just gonna have to take the time to flatten it by hand do you have to flatten the whole thing though no I tried to hold it flat on the stone as I work it but I'm only worrying about flattening the last inch three quarters of an inch or so that is the reference surface that you need and that will give you all you need to have a nice sharp chisel of course you can't make a tool flat if your sharpening surface isn't flat as well and this is another cause of frustration for many woodworkers you if you rub a tool on a dish surface your edge will come out shaped like that surface so you're effectively giving your edge a hollow or a belly to shape if you strip with sandpaper then you're gonna have to use some tempered glass or some granite or something you know is perfectly flat underneath it if you use water stones you have to maintain them regularly a lot of people do it after every sharpening they reflect on their stone that's why for hand sharpening I prefer to use Diamond stones because they stay flat without maintenance I like the trend stones because they make sure that the solid steel substrate they're not laminated is perfectly flat within a half a thousandth of an inch from end to end that's twice as flat as the standards used by everybody else we made a video about Diamond stones a while back I'll put a link to it in the notes below this video if you're interested we also made another video about whatever sharpening medium you're using sandpaper stones pace whatever about the different grits that you should use and how sharp is just sharp enough I'll link to that too just click on show more if you're on youtube next time we do a sharpening video we're gonna talk about leather straps an ancient sharpening tool that can give you big results for more great tips tricks and tutorials designed to make you a better woodworker check out stumpy nubs woodworking journal you can read and subscribe for free at stumpy nubs dot-com

Channel: Stumpy Nubs

Views: 810,940

Rating: 4.8783002 out of 5

Keywords: woodworking, stumpy nubs, tool sharpening, wet stone, whet stone, oil stone, water stone, knife, scissors, diamond, trend

Id: 5yj16u7udlw

Length: 11min 26sec (686 seconds)

Published: Fri Nov 02 2018