Scrubbing Stroke

[Trout Hound]

Whenever I try to use a back-and-forth scrubbing stroke to speed steel removal, usually when trying to lower an edge angle, I end up messing up the shoulder. Seems like no matter how I try to keep the angle consistent, I end up rounding off at least a bit. Is there a way to do it and keep the bevel nice and clean? Thanks!

 

[HeavyHanded]

Whenever I try to use a back-and-forth scrubbing stroke to speed steel removal, usually when trying to lower an edge angle, I end up messing up the shoulder. Seems like no matter how I try to keep the angle consistent, I end up rounding off at least a bit. Is there a way to do it and keep the bevel nice and clean? Thanks!

Try to work at a diagonal across the stone. Every time you start and stop there will be a tendency to lag, the spine will want to move first and the edge will follow. This tendency will be strongest if you work straight back and forth into the grind path, and if you work dead parallel to the grind path it will have a tendency to rock/pivot on the bevel a bit, though this seems to be easier to accomodate than the straight perpendicular scrub.

By aligning the edge at a 45° to the grind path you will introduce added stability. There will be more surface area of the bevel on the stone, and also the entire thing will have more resistance to moving at different rates from spine to edge at the start of each motion - you increase the "beam strength" of the arm/hand/tool.

Also, keep your off hand fingertips right on top of where you're making contact with the abrasive surface. Keep them as close to the abrasive surface as you can without grinding off the skin. This keeps all the stabilizing effect right on top of the bevel - as it moves further up the blade face toward the spine, it looses its ability to assist in holding the edge stable will begin to work against you by contributing to the edge rocking.

If you're working with the edge facing you, just keep the fingers low on the blade face. If working with the edge facing away it is very important to keep the fingers of your support hand bent in a slight hook shape to keep the force they apply directed to the bevel and not higher up the blade face where it might induce wooble.

Use short, easy movements - the further you move your hands the more correections your skeleton will have to make. When I'm setting the bevel initially I might only make a pass of an inch or two. This will open up a bit as the geometry flattens out and I have more to go by, but it will always be easier to maintain tight tolerances by asking for fewer mechanical corrections. Study the hands in motion and try to see where you're allowing it to move - actively beat back these weak spots in your technique. Is relatively easy to make reasonably clean geometry, but if you want to make improvements you have to figure out where its not working as well as you'd like. This may require you hold the knife/tool in a very different manner than you are currently, or maybe just a small shift in how its supported by the digits, where the handle crosses the underside of your knuckles, bridge of the hand. Work on consistency as much as possible, apply common principles across as many tool shapes as possible.

As you work, stop often to inspect the edge and where its grinding. Learn to correlate the sensation of it moving over the abrasive with where you are on the edge. When working I also tend to lower the spine intentionally for a light pass or two as I go to get the feel for the shoulder on the abrasive, then I elevate the spine just till the sensation drops off. This keeps me working methodically from shoulder to edge and not just floating betwee the apex and the shoulder. I use this strategy right up till the polishing stone and even on my Washboard with paper I will sometimes lower the spine so I can just feel the shoulder dragging slightly and elevate just enough to make that sensation drop off. When you find yourself sandwiched between the sensation of the shoulder dragging and the apex dragging (by this point you will have ground a fresh edge and a burr should be visible) you know you have created a bevel as flat as your mechanics and tactile awareness can produce, and that shoulder should be equally as crisp.

Lastly, muddy stones will invariably soften the shoulder and possibly even scratch the blade face above the shoulder. For crisp shoulder transitions use a hard stone or wipe/rinse etc the surface of the softer stone as you go.

Ahhh, short and easy to understand! I've nailed it again!
Hmmm, maybe a drawing or two is in order.....

 

[bucketstove]

I have found the best way to scratch up my blade is stone in one hand, knife in other, and fast fast fast fast scrubbing passes
I get the angle I want and I scratch up the whole blade

works for me

 

[bgentry]

Everything HeavyHanded said is excellent information. If only I could *do* it all like he says! I've only got a tiny bit to add. See below.

Use short, easy movements - the further you move your hands the more correections your skeleton will have to make.

Skeleton. Think all of all of the joints in your body involved in making these back and forth passes. The fewer joints you can move, the better you will do. I've found that rocking my body and keeping my arms relatively locked gets me better results. When I do it correctly, my shoulder joints move almost zero. The elbows also very close to zero movement. The wrists absolutely stay locked. I don't mean "locked" as in having your body super tense or exerting muscular force. Just a lack of movement in the joint.

I tend to rock at the ankles and hips, so my whole upper body moves together. When I do it correctly, my results are noticeably better.

Brian.

 

[Bazzle]

Circles!

 

[Obsessed with Edges]

All of Martin's (HeavyHanded's) advice is excellent. +1 to keeping the blade at a diagonal to the stone & direction of stroke; that's what works well for me in using the scrubbing technique, and for most other work as well. It works better because the length of the blade is oriented more with the direction of movement, and that will add stability that's otherwise missing when the bevels/edge are directly perpendicular to direction of movement (causing pivoting up/down or forward/backward).

Holding the knife in a manner that minimizes other superfluous movement (up/down, pivoting/rocking, etc) also adds a lot of stability. You want to minimize bending/flexing of the wrists during the stroke, for example. And keep the handle firmly bedded in the palm & pad of the hand, for control; the ring & pinky fingers lend a lot of control for this, much in the same way they'll stabilize a golfer's grip on the butt of the club in the leading hand of the swing (left hand for a right-handed golfer). For most, the hold will be a matter of experimentation & close observation, to see what grip/hold is both stable and comfortable for heavy/long-term grinding on the stones. Once that's figured out, it greatly contributes to the fine touch needed for later finishing & refining steps, and will become essentially 2nd nature and 'automatic' with practice.


David

 

[mycough]

All of Martin's (HeavyHanded's) advice is excellent. +1 to keeping the blade at a diagonal to the stone & direction of stroke; that's what works well for me in using the scrubbing technique, and for most other work as well. It works better because the length of the blade is oriented more with the direction of movement, and that will add stability that's otherwise missing when the bevels/edge are directly perpendicular to direction of movement (causing pivoting up/down or forward/backward).

Holding the knife in a manner that minimizes other superfluous movement (up/down, pivoting/rocking, etc) also adds a lot of stability. You want to minimize bending/flexing of the wrists during the stroke, for example. And keep the handle firmly bedded in the palm & pad of the hand, for control; the ring & pinky fingers lend a lot of control for this, much in the same way they'll stabilize a golfer's grip on the butt of the club in the leading hand of the swing (left hand for a right-handed golfer). For most, the hold will be a matter of experimentation & close observation, to see what grip/hold is both stable and comfortable for heavy/long-term grinding on the stones. Once that's figured out, it greatly contributes to the fine touch needed for later finishing & refining steps, and will become essentially 2nd nature and 'automatic' with practice.


David

Well said, I believe you and Martin have this thread sewed up tight.......
Russ

 

[Fred.Rowe]

Get yourself a set of degree wedges; it will cut your sharpening time in half and produce a better edge in the process.

Martins advise is spot on as well.

Fred

 

[HeavyHanded]

Here's a quick sketch I made a while back to accompany a conversation with friends about where my freehand technique had gone. Isn't exactly how it works but pretty good for conveying the general idea.

This method won't work 100% with every tool/blade-handle configuration, but is still pretty universal. Biggest advantage is that its not only stable it incorporates common assignments as much as possible. I can cross scratch patterns at right angles if desired, can sweep the pattern into the cut or away from it. Can also be utilized in a perpendicular or parallel scrub or any angle in between with no real change except how I address the stone. Took some getting used to, but like so many of my small mechanic evolutions, it made a consistent positive impact shortly after adopting it. For me it has allowed some notable increases in speed with no loss of precision.

 

[mycough]

Get yourself a set of degree wedges; it will cut your sharpening time in half and produce a better edge in the process.

Martins advise is spot on as well.

Fred

Where would a fella get a set of degree guides? Sounds handy as heck.
Russ

 

[fmendez]

Here's a quick sketch I made a while back to accompany a conversation with friends about where my freehand technique had gone. Isn't exactly how it works but pretty good for conveying the general idea.

This method won't work 100% with every tool/blade-handle configuration, but is still pretty universal. Biggest advantage is that its not only stable it incorporates common assignments as much as possible. I can cross scratch patterns at right angles if desired, can sweep the pattern into the cut or away from it. Can also be utilized in a perpendicular or parallel scrub or any angle in between with no real change except how I address the stone. Took some getting used to, but like so many of my small mechanic evolutions, it made a consistent positive impact shortly after adopting it. For me it has allowed some notable increases in speed with no loss of precision.

Those are good and clear drawings; do you have an art background?:thumbup:

 

[mycough]

Those are good and clear drawings; do you have an art background?:thumbup:

After following his threads and posts over the years I wondered if Martin might have been a teacher. Russ

 

[HeavyHanded]

Those are good and clear drawings; do you have an art background?:thumbup:

Thanks, I'm mostly self-taught from a lot of books and comics. I also did the drawings for a provisional patent and like to tinker, so I'm always sketching my plans ahead of time - really helps if there isn't too many eraser marks! Back in the day I used to do tattoo flash and custom art for a couple of artists locally too.

I keep meaning to update my avatar with something a little nicer.

After following his threads and posts over the years I wondered if Martin might have been a teacher. Russ

I do a small amount of kettlebell instruction from time to time. I've also taught my share of press feeder tenders and operators over the years, but my teaching style has really mellowed over the years...Was once described to my face by a new guy I was training as "the biggest a**-hole I've ever known!" I took it as a compliment and am pretty sure it was meant as one - pressrooms used to be kind of a rough place.

 

[fmendez]

I taught art for many years, primarily painting, drawing and printmaking. My avatar is one of my lithographs which I also have it done as a tattoo. It is good to have other artist in the forum with original art as avatars.

 

[Chris "Anagarika"]

Martin,

Thank you for the diagram! I don't always use same method, but the principle behind it is very clear and can be transferred to how I do it. :thumbup:

Nice avatar. I almost didn't realize it's you

 

[fmendez]

And a self portrait? That is even better.

 

[HeavyHanded]

Welllll, its not a self portrait so much as inspired by - I'm nowhere near that good-looking!

 

[Trout Hound]

My thanks to everyone, especially Martin for your extremely thorough explanation. I gave this a try tonight and got much better results. This will certainly speed up my sharpening. Two follow up questions:

Could you use a scrubbing stroke on a diamond hone? I was trying to imagine doing it with little enough pressure not to wreck the diamonds, and I wasn't sure if that would work.

Also, I got a hazy shoulder transition when using my Crystolon stone with mineral oil. Dried it off and the problem stopped, which leads me to believe it's caused by mud on the stone, not my angle. Any way to keep the oil but get a nice clean shoulder?

Thanks!!!

 

[HeavyHanded]

My thanks to everyone, especially Martin for your extremely thorough explanation. I gave this a try tonight and got much better results. This will certainly speed up my sharpening. Two follow up questions:

Could you use a scrubbing stroke on a diamond hone? I was trying to imagine doing it with little enough pressure not to wreck the diamonds, and I wasn't sure if that would work.

Also, I got a hazy shoulder transition when using my Crystolon stone with mineral oil. Dried it off and the problem stopped, which leads me to believe it's caused by mud on the stone, not my angle. Any way to keep the oil but get a nice clean shoulder?

Thanks!!!

You can absolutely use a scrubbing stroke on a diamond hone - just have to remember to go nice and light. Its the finishing passes that will count, so do the work with a scrub and transition to a light leading pass to finish/deburr.

That haze you are seeing on the Crystalon is exactly as you surmise, a result of loose grit in the oil - the exact same condition arises on a waterstone once it begins to generate some mud, esp if use with a scrub. It becomes a hybrid grinding/lapping exercise and that's what keeps burr formation to a minimum and prevents deeper scratches at any given grit value- so bit of give and take. It will create a bit of shoulder haze, especially at the lower grit, keeping the stone relatively clean will lessen this as will allowing the stone to dry out a bit for the final bit of work.

It takes little more than a few passes on a sheet of paper wrapped around the same Crystalon stone (wiped dry) to clean it up and shine a lot of the haze away. You can also drag a sheet of paper across the wet stone to mop up some of the grit and it makes an excellent stropping compound - the SiC grit as broken off the surface has a lot of very sharp edges that graded SiC and AlumOx do not possess - makes a great catchy edge.

[video=youtube;DF2Y7Hha0MQ]https://www.youtube.com/watch?v=DF2Y7Hha0MQ[/video]

 

[Tony18]

I don't like using oil it's just to messy for me. I prefer water with a little Dishsoap, it's been working out great for me. I take a used water bottle fill it most the way up put some Dishsoap in & gently mix it up to not make so many bubbles, use my knife to poke a few holes in the cap & spray it on my stones when needed. Real cheap & effective with easy clean up. I use this with my Crystolon as well.