Sandpaper sharpening - first try - what'd I do wrong?

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tuffluv

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Feb 24, 2015
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I know I need much more experience sharpening this way but I thought I'd share the results of my first attempt at sandpaper sharpening.

Just to get the hang of things I bought 800, 1500, and 2000 grit wet/dry automotive 3M sandpaper from Wally world. I used the blade on an old leatherman Pulse multi-tool as the test subject. My flat surface consisted of a 1-ft square marble tile I got for free. I used a little dish soap mixed in with the water and clamped the sandpaper to the tile.

I marked the edge with sharpie and seemed to match the existing bevel pretty good when sanding. I only made 20 edge-leading passes on each side of the blade with each grit of paper. No stropping took place.

The blade seemed to get sharper, but only slightly. I guess I was expecting more.

Any advice? Should I use more grits of sandpaper? Should I make more passes?
 
You'll need to start at a lower grit for actually repairing a bevel. Your first grit determines your end sharpness. Practice getting good edges with one low grit like 220-400. Why bother polishing a bad initial edge right?

Don't progress by counting number of strokes. Hand sharpening is about getting a feel for what your doing. Once your able to get good initial edges you can practice this by raising a burr with each grit so you know your ready to go on. Once you get a "feel" it will be much easier to know when to progress while doing alternating sides

I dont do edge leading strokes with sandpaper. Use a stropping motion instead.
 
I'd also recommend using it dry, clean it off with and eraser or synthetic wine cork when it loads up.

All the same rules apply to sandpaper as with regular stones - raise a burr, flip, remove.

With the sandpaper, a real light leading pass works great for removing the burr, then finish with a few super light trailing passes. As you get more used to it, you can use a leading pass, scrubbing back and forth pass, trailing only, whatever - but you should always finish with a few very light trailing passes to get the most from it.

Keep the amount of pressure very light and clean it often. Too much force can ruin the paper prematurely, and will also cause the edge to round as the paper sinks. Even over tile, the paper will have some give, the lighter you can go the flatter the end result.

The first video on the website linked in my signature below details some sandpaper sharpening best practices on a sharpening block I make, the bulk of the content applies to all sandpaper sharpening on a hard backing. Might be a helpful watch.

Martin
 
Start with nothing finer than 320. A piece of wood the size and shape of a long stone (you're saving some bucks here), you needn't bother with a soft pad for convex, that will come naturally with angle holding errors. Use it dry, trailing edge. Experiment.
 
Update from second try last night:

started with 320, 600, 800, 1000. Used edge trailing strokes. Felt burr development for the first time. Still no stropping.

When finished, the blade felt sharper and cut paper better.

It's a good edge but I suppose I'm expecting a light saber.


What is a good objective measure of when the blade is sharp enough? I suppose the answer is "it's sharp enough when it can handle the task I need it for." Any better answers out there?
 
That answer you gave is spot on. If you want to test sharpness, push cut newsprint. No slice...push cut.
 
tuffluv said:
Update from second try last night:

started with 320, 600, 800, 1000. Used edge trailing strokes. Felt burr development for the first time. Still no stropping.

When finished, the blade felt sharper and cut paper better.

It's a good edge but I suppose I'm expecting a light saber.


What is a good objective measure of when the blade is sharp enough? I suppose the answer is "it's sharp enough when it can handle the task I need it for." Any better answers out there?
Click to expand...

'Sharp enough' is very subjective, but your assumption is generally good. I think your Leatherman Pulse's blade is 420HC, which should usually respond very well to sandpaper sharpening. MOST of the noticeable differences, between 'sharp enough' and 'light saber sharp', will happen as the edge angle is lowered to more acute thinness; especially @ 30° inclusive or lower. I ALWAYS go a bit lower in angle, as the first solution to improve perception of sharpness. The trade-off might be with edge durability, if going too thin (edge may roll too easily); but, as I see it, that's part of really learning about the capability of the steel, and I see no reason to fear doing what's needed to figure that out. Most modern knives in relatively common steels like 420HC can handle normal (not abusive) EDC tasks at angles down to 25° inclusive or so. If 'light saber' sharpness is your goal, thinning the edge geometry is what I'd do first. IF your Pulse's edge is as thickly-ground as on my Wave's blade, the edge geometry from the factory is pretty obtuse (wide), so thinning it should improve cutting performance.

With sandpaper, results will get much, much better if you stick or adhere the paper to your hard backing with adhesive or similar means. I use a spray adhesive called 'DAP Weldwood Multipurpose Spray Adhesive', which can be used as a temporary bond for the paper; it's peelable and fairly easily removed, after you're done with a piece of the sandpaper. Anything that keeps the paper from moving or lifting/rolling/curling will help to produce edges that are much crisper, minimizing rounding of the apex (that's the other important part of attaining 'light saber' sharp edges).


David
 
Last edited:
Obsessed with Edges said:
'Sharp enough' is very subjective, but your assumption is generally good. I think your Leatherman Pulse's blade is 420HC, which should usually respond very well to sandpaper sharpening. MOST of the noticeable differences, between 'sharp enough' and 'light saber sharp', will happen as the edge angle is lowered to more acute thinness; especially @ 30° inclusive or lower. I ALWAYS go a bit lower in angle, as the first solution to improve perception of sharpness. The trade-off might be with edge durability, if going too thin (edge may roll too easily); but, as I see it, that's part of really learning about the capability of the steel, and I see no reason to fear doing what's needed to figure that out. Most modern knives in relatively common steels like 420HC can handle normal (not abusive) EDC tasks at angles down to 25° inclusive or so. If 'light saber' sharpness is your goal, thinning the edge geometry is what I'd do first. IF your Pulse's edge is as thickly-ground as on my Wave's blade, the edge geometry from the factory is pretty obtuse (wide), so thinning it should improve cutting performance.

With sandpaper, results will get much, much better if you stick or adhere the paper to your hard backing with adhesive or similar means. I use a spray adhesive called 'DAP Weldwood Multipurpose Spray Adhesive', which can be used as a temporary bond for the paper; it's peelable and fairly easily removed, after you're done with a piece of the sandpaper. Anything that keeps the paper from moving or lifting/rolling/curling will help to produce edges that are much crisper, minimizing rounding of the apex (that's the other important part of attaining 'light saber' sharp edges).


David
Click to expand...

This is good info, thanks a lot Man! Russ
 
I use wet sandpaper for sharpening on glass. I would definitely start at a grit of around 220. Work up to 600-800 then test how it feels. Continue to higher grits to refine the edge. I use 220, 400, 600, 1000, 2000, 3000, 6000.
 
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