Convex bevel troubles

[James Pallas]

When I said I learned to sharpen that way. It was done on the job on the end of a saw horse on a combination carborundum stone with a little bit of 3 in 1 oil. You shot for a flat bevel but it usually ended up somewhat convex over time. I don't do that now because I don't have to. Paul Sellers can do as he pleases and teach as he pleases. We can say what we want but it's difficult to argue with results. He does in fact make some very nice things and people seem to get a lot from his teaching. YMMV
Jim

[David Myers]

I don't sharpen most tools freehand. I will only say that PS occasionally mentions he lowers the angle to cut back on the convexity then raises it again to get back to the edge.

I don't know how often or on what grits he does so.

And I agree with the comment above. He makes good projects, good videos with tools accessible to any handtool enthusiast. Feel free to adapt or discard his methods, just get your tools sharp.

[Prashun Patel]

While he doesn't say this, I believe his method works for some because the rocking makes it psychologically easier to hit the edge on the front part of the stroke.

I prefer to freehand only because I am lazy and it's quicker than setting up a honing guide. Hollow grind, flatgrind off the Worksharp, or convexly beveled after repeated freehand honings: with enough practice, you will learn to find the edge and recognize when you have it.

At the risk of hijacking, I have a question: I have lately identified that when I'm honing the edge properly, there is a distinct sound and feel. It drags almost imperceptibly more than when I'm on the bevel and not quite at the edge. It also sounds "scratchier". I can't explain why that is, and I suspect it's in my head. Does anyone else experience this?

[Derek Cohen]

The rounded bevel method is useful for the secondary bevel of mortice chisels, which is where I use it (and only there), since a guide does not work well here. To ensure that I do not go over 35 degrees, I keep a wooden guide on hand. This is angled at 35 degrees.



Start at the low end and pull to the high angle ...



This is what one should end with ...



Regards from Perth

Derek

[Jim Koepke]

I don't know how often or on what grits he does so.

One of Mr. Sellers videos made me lose any credence in his 'teaching' abilities. It has him saying one only needs to hone their blades up to a 220 grit because that is where people stop sanding before they apply any finish.

There were other videos of his that also made me think he doesn't have much of value to help me.

As stated before, more than one of my posts has contained comments about how a convex bevel may be useable, but it is surpassed by almost all other methods.

One piece of literature suggests in the early days of Sheffield tool makers tools were hollow ground because the workmen at the time would refuse anything with a convex bevel.

Often the "quick and easy way" can lead to learning bad habits.

jtk

[Steven Mikes]

Thanks for the input everyone, looks like I will be avoiding free-hand sharpening for awhile (and just using the eclipse-style honing guide I already own). Unfortunately I don't currently own a bench grinder. Would one of the $40 6" grinders from the BORG be sufficient, with a 60-grit aluminum oxide wheel as suggested by Doug?

I did finally fix the bevel with the help of some courser sandpaper, finally back to a good edge that's cutting well again. Now I'll have to do the same to my other blades *sigh*

[Jim Koepke]

Thanks for the input everyone, looks like I will be avoiding free-hand sharpening for awhile (and just using the eclipse-style honing guide I already own). Unfortunately I don't currently own a bench grinder. Would one of the $40 6" grinders from the BORG be sufficient, with a 60-grit aluminum oxide wheel as suggested by Doug?

I did finally fix the bevel with the help of some courser sandpaper, finally back to a good edge that's cutting well again. Now I'll have to do the same to my other blades *sigh*

I have no idea how well the grinders from the Borg may be.

My "grinder" is actually a flat disk (Veritas) sharpening system. So far all of my tools with sharpening needs have been able to be worked on this setup. That includes knives, hatchets, axes, shovels, metal working tools, woodworking tools and the occasional piece of wood.

A regular grinder will produce a hollow grind which makes hand sharpening easier. A flat disk set up produces a flat bevel. Over time my chisel bevels may get out of true flat and then it is time to reestablish the bevel.

One advantage of the Veritas sharpening system is changing grits is quick and easy. With a regular grinder you may have two wheels and the changing of grits is likely to be forgone as it is a bit of work.

jtk

[Doug Hepler]

Steven,

I had the grinder for general work before I adopted the regimen I described earlier. So, my investment was actually just two new ALO2 wheels and two tool rests. AND i use it to sharpen turning chisels (which is a different thing). If you don't need a grinder for purposes other than sharpening hand tools, I recommend that you consider the Veritas flat disk system that Jim mentioned above.

If you want a grinder, Fine Woodworking did a review back in 2012 and recommended the Porter Cable PCB575BG. The basic grinders are all about the same, two abrasive wheels on a motor driven shaft. If it runs true it will be OK. The amenities are what differentiate one from the other -- shaft length (you may want to move up to CBN wheels some day), variable speed, work light, tool rest. If you plan to sharpen chisels I suggest that you also get a Veritas tool rest.

Doug

[Patrick Chase]

While he doesn't say this, I believe his method works for some because the rocking makes it psychologically easier to hit the edge on the front part of the stroke.

Yeah, but it's like a heroin addiction in that you have to keep rocking it more and more to ensure that you continue to hit the high...err...edge that you crave so much.

[John Schtrumpf]

Yeah, but it's like a heroin addiction in that you have to keep rocking it more and more to ensure that you continue to hit the high...err...edge that you crave so much.

I have watched a sharpening video of his. He works rapidly and does a lot of strokes. My theory is, if you do enough strokes, eventually you will have hit the edge a few times.

As for me, my muscle memory is unreliable. So I register the existing flat bevel on the stone and work that.

[Don Dorn]

I'm the odd man out. Having tried several methods over the years, I had settled on Rob Cosmans for awhile. Now, I'v'e been using the Sellers method for years now. I really like it because with three diamond stones and stropping in about 5 minutes leaves me with an edge that slices through receipt paper with just blade weight and seems to keep through an average project.

As to the convex, many are probably right in that it happens incidental to the process as opposed to it being intentional. That said, it doesn't bother me. When they get too blunt, I just grind, just as I would when you get too much of a secondary bevel on a flat or concave iron. I use the Ian Kirby system on a slow speed grinder and because I stick with Stanley irons, it takes no more than about five minutes. In any event, it works for me for both chisels and plane irons.

For router plane blades as well as beading cutters, I follow Chris Schwarz way of "reversing" it. I sharpen the flat side until a burr is created on the work side. Then, just rub that off with a slip stone or final stone. I think I"m done with learning or experimenting with sharpening and grinding. It's faster than its ever been and I'm very happy with the results.

[Robert Hazelwood]

I don't make convex bevels on woodworking tools, but I do use them on hatchets and axes. I tend to think of them as a blended set of bevels, and use the same philosophy as I do with a flat primary and secondary bevel. That is, the majority of the metal is removed behind the edge. If you remove too much near the edge you will end up with an obtuse edge. With the coarse stones I work a convex bevel starting at the base of the bevel and working closer to the edge, but not quite there. With the penultimate stone I will do much the same, but at the end of the step I will just work the edge enough to raise a burr, careful not to overshoot the existing angle. Then I will refine the edge and remove the burr with finishing stone.

I think you could do much the same with a chisel or plane iron. In fact, you could sharpen in the Sellers style but deliberately work to a lower angle than you want to finish with, then hone a small secondary bevel at your desired edge angle.

I would not give up on free handing. It's more enjoyable, less cumbersome, and kind of empowering to do it freehand. You just need to keep your angles under control. I really think the reference blocks I mentioned in an earlier reply would be helpful (Derek also posted a different version, either would be effective). Getting a grinder would be useful of course, and freehand honing at a steady angle seems easier than trying to return to the same angle on every stroke after sweeping through a range of motion.

[David Bassett]

... Would one of the $40 6" grinders from the BORG be sufficient, with a 60-grit aluminum oxide wheel as suggested by Doug? ....

For home / hobbyist use I don't think those grinders would be a problem, unless you got an unusually poor example. (There is a reason industry doesn't use them though! Less power, cheaper bearings, more runout, etc. etc. etc.) The biggest problem with those cheap grinders are the wheels, which are not friable enough for our harder steels, and their tool rests, which are... inadequate. The hard gray wheels that come with the big box store grinders are designed for mild soft steel and don't shed dull particles quickly enough to stay sharp and cut harder tool steels. It seems like turners more commonly use dry grinders and the go to cheapie there seems to be the Rikon 8" which goes on sale for $100 every so often. It comes with less awful wheels, so you don't have the expense of upgrading those right away. (Also, there seems to be a greater selection of CBN wheels in 8", for when you get tired of ever shrinking friable wheels. ) As for the tool rest, there are a number of good options out there. Some will even argue you can freehand on a grinder as well as on stones, but even free handing my angle I like a tool rest to brace my hand against. (Brushing the wheel is... unpleasant. Never tried catching a finger in the mechanism and I make very sure that I won't!)

[Patrick Chase]

It seems like turners more commonly use dry grinders and the go to cheapie there seems to be the Rikon 8" which goes on sale for $100 every so often. It comes with less awful wheels, so you don't have the expense of upgrading those right away.

I've never used 1/2 hp Rikon (which I suspect is what you're referring to) but I have the 1 hp version that usually goes for $200 or so. It's a remarkably nice grinder even considering the cost. The wheel bushings are reasonably large and solid discs vs the stamped sheet metal ones on cheaper grinders, and the result is improved trueness/tracking. If you're going to upgrade to CBN anyway then this may not matter, as CBN wheels tend to run true to begin with, but it's a significant benefit for conventional wheels.

The Rikon wheels are OK and significantly better than Borg fare, but on the hard side compared to the ones that WWing retailers sell. The Rikons have White Alumina (WA) abrasive and grade N binder. For comparison LV's "white friable" wheels are also WA, but grade H. I've dressed a couple of my Rikon wheels for use with concave tools (their hard binders are advantageous for holding profiles) but you have to be a little careful to avoid burning. If you use a light touch and dress reasonably frequently it's not a big deal, though.