Thread: The Unicorn method

Thanks Derek. Appreciate it.

And yes i am going for the 8" half speed.

Cheers

Winston Chang has make another short video about buffing the Unicorn edge on chisels. This is excellent and shows what is involved and what occurs. Necessary viewing!

Sharpening chisels with a buffing wheel on Vimeo

Keep in mind that Winston uses a simple drill and stitched wheel. This takes more time than my set up simply because the drill rotates at a slower speed. David uses a bench buffer. I went for another bench grinder rather than a buffer for the options down the track. The half-speed Rikon I have is available from a few places (Google). My other half speed bench grinder is from Carbatec many years ago, and no longer available.

Regards from Perth

Derek

Hi Derek , i have followed this with much interest and dived in.I have a Vicmarc 200mm slow speed grinder also no longer available with 180 grit CBN wheel, great purchase.U tube on cotton rag buffing wheels showed them fitted to the grinder by a tapered spindle,my grinder has a 14mm thread that would accept the spindle, however the available 14mm Josco tapered spindle doesn't fit , Duhh,dont want to pursue time consuming search for a fit if it exists, looking at your first post, perhaps you drilled the center of the buffing wheels to fit your grinder shaft , added an extra to take up the space on the shaft,how did you fit the wheels to your grinder? the 14mm tapered spindle fitted my 5 inch angle grinder, clamped the grinder to the bench , screwed the buffing wheel on ,green honing compound and buffed a chisel after hollow grind, honed bevel, yes amazing sharpness , it works,but would prefer the bench grinder for safety of use , greatly appreciate your effort in this thread , thanks Ross

Yes, I drilled/enlarged the hole in the buffing wheel to fit the spindle of the grinder. I could have purchased a tapered spindle for it. The Rikon came from Beyond Tools, and they have the spindles in stock (fabulous store!). The reason for not getting the tapered spindle was simply that I wanted to ensure that the wheel spun perfectly straight (no wobble). Washers on each side help take up space. I also added the small buffing wheel from Tormek at the side.

Regards from Perth

Derek

re: the above and not needing to drop the angles on a chisel. I've long buffed or rounded mortise chisel tips (even when they're sharpened at 35 degrees or so, the chisel tip holds up better if it's not at a crisp apex).

Bill Tindall here hasn't yet changed the angle on anything that he uses and is just looking to get the additional sharpness and not have edges failing. The additional sharpness is counterintuitive until one gets way deep in the weeds thinking about edge thickness and follow-on geometry. That is, what seems conceptually sharp to us is an infinitesimally small line, but the reality is that the thickness of an edge itself just needs to be below a critical point. When we use razors for a long time, this line thickness is kept small, but the edge is rounded by linen and leather for a couple of hundred shaves.

Shaving with a straight razor that isn't modified in this way results in a failing edge within a week or two. The unstropped edge is sharper at the start, but the difference is mostly felt on the skin that's cut behind the pore. The hairs are indifferent in resistance to the edge that's been stropped and rounded. vs. the super crisp edge because the radius and thickness of the edge is below a critical point. Ideal shaving comes when that point is below the critical point for the hair and above the critical point for the skin.

Long story short, it's fine to buff everything. I have been buffing or hand rolling (on a slow stone) for a very long time and not noticed much extra resistance (collectively, it's less when the edge doesn't fail), but the whole unicorn geometry thing comes up (for bench chisels and paring chisels) because once you get to that point, then little operations that seem hard to a beginner (paring off waste on a tenon to a marked line without tons of resistance or pushing the line down with wedging resistance) become really easy.

Hopefully, nothing I've said makes it out like I have been suggesting against just buffing the edge you start with. Bill tells me that he has no interest in going beyond that.

I am an actuary. I always think of everything not as in the moment, but the moment plus the present value of all future moments (efforts). It may not be worthwhile for someone to chase all of the details of this for bench and paring chisels (and gouges, etc) right away, but as you go along with chopping and paring chisels, dropping the primary angle and secondary are just reasonable efforts to get as much as you can out of this method - for nothing. or rather for gain.

You'll be doing basic operations in woodworking that you wrote off in the past.

Even if ignoring the buffer talk entirely, I have been slowly beating the drum of finishing on a slow stone and applying "the roll" to the edge. Only Brian Holcombe ever identified what I was talking about and everyone else wrote it off. when you just buff a chisel as it already is to improve things, that's a machine version of "the roll". The roll has ..

...wait for it. Two functions.

1) people with high laziness or low sharpening skills will suddenly finish edges completely (which everyone thinks they do, but most people don't - you can't see the last thousandth or two of minor damage and most people stop when they can't see anything, or before that)
2) it's protective of the edge without getting the cutting width (vs. the wedging width above the cut) above the critical level to sever things easily

The same thing the buffer is doing.

Thanks for the link - a great video!

Although initially I was thinking a drill is a bit of a lo-fi or 2nd rate solution... a cordless drill with a battery is perhaps a more practical option for those with limited space?

It would fit under the bench or a hook or holstered on a holder on the wall or in a drawer and be whipped out as needed instead of needing a dedicated station.

I wonder if there are many downsides to using a drill, other than being perhaps unwieldy for plane irons?

Drill is a little slower and leaves you with one hand to do the buffing, but it works perfectly fine and is better than stropping by hand on leather by a mile.

I just tested a loaded strop to get a similar effect with the yellow compound (about twice as fast as the green).

I counted 50 strokes, and still there was some wire edge hanging on a chisel - it took another 50 (100 total) to get a similar effect to any buffing wheel and the edge is slightly less fine.

The other benefit of the drill vs. a buffer is that a drill arbor is about $10 usually with a couple of buffing wheels. They're a bit soft like winstons, but they work fine once the drill is spun to speed.

Where the buffer starts to separate itself is on bigger edges (knives, drawknives, etc) and being able to use two hands.

Thanks David

In terms of thinking about it, an analogue that comes to mind is what happened with aeronautics. For a long time aircraft designers were assuming a needle-point was the most effective shape for an aircraft fuselage.

However testing eventually demonstrated that the teardrop shape was in fact the most effective in many speed ranges.

The analogy is not of course perfect (the tear-drop superiority involving functions of airflow behind the leading edge) but in broad terms...

Same kind of concept, it is, though. Initial work was probably concerned with cutting through the air at the tip, and subsequent study found there was more to it than just making a point to "cut through".

Always liked the pointy planes as a kid, though! I was born after the 747 was already in the air, but always liked the delta dart and the b-58 look. They look more dangerous with the point.

Spoze one could always make their own polishing wheel jig....

-- threaded rod and a few nuts/washers
-- 2 ball bearings
-- a [__] shaped holder of MDF/whatever

-- bore two holes in either side of [ ]
-- push in bearings into holes
-- hold bearings in place with flat head screws

-- insert thread partly, fit wheels and huts/washers, push rest of way through
-- tighten nuts/washers so wheels are where you want them

--> Attach old drill or variable speed router to the threaded rod and GO FOR IT!!!*




EDIT - ah, look! Someone beat me to it! Dammit internets!

photo-large-hd.jpg diagram.jpg buffer7.jpg



*obviously this will need a cradle to hold it in place.

Drill arbor and a couple of cotton buffs as well as some other buffing bits (from china, so I'm sure it's available there, too) is about $15.

If using wheels that are harder (like felt) then you will have to fiddle with angles a little bit and the speed will need to be lower. MDF, hard leather, felt are all pretty harsh on edges at very high speed (MDF may be dangerous if it breaks).

Felt and layered leather can be made to work well, though - no doubt about it - they are just a little bit less forgiving and need lower speed.

David and all,

Just reporting back on my attempts. I had another go and think I hit it just by being a little less nervous.

MY GOODNESS.

The beater chisel I posted previously was measured (after I found my protractor) and was actually about 17 degrees.

IMG_20200808_070152.jpg

Now this is a said to be ridiculous angle for tough work. I think I have only seen/read one occasion where an angle this narrow was ground - a video where Rob Cosman grinds one and from memory says to the effect it will void any warranty / be for very particular use such as paring very soft wood.

Not possible to use a mallet last night/this morning to avoid waking anyone up. But just on finger pressure push stroke it had no problem paring end grain of a little piece of tassie oak.

IMG_20200808_070444.jpg

Even after quite a bit of mucking about on the end grain, I went back to tidying up a little project yesterday, flushing some dowels and flush-trimming some box edges. It was as sharp as when I started after quite a lot of action.

Unless any problems develop it seems this now resolves the question of the final honing and stropping all in one.

The next arms race will be the convenient bench setup for hosting a cloth wheel (and in particular, something to collect the fluff and grit...)

That is a paring chisel bevel right there!! about the same angle as a straight razor.

glad it seems to be working so far. Not sure if this whole method will have any lasting effect (sometimes things like this just blow away once the flurry is over), but I wonder if any toolmakers are watching these developments.

I suspect that this is very uncommercial though - no-one would make money out of equipment given how widespread all the equipment is.

I am already plotting a little wall-mounted box holding a corded drill and wheel for touch-ups though...