Lapping a benchstone?

S

Squashfan

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Jun 6, 2012
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I have a two sided Lansky benchstone which I use for cheap knives. The stone is dished on the fine side. I have seen mention of lapping or flattening a benchstone. I know you need a rock or maybe concrete. And that you rub the benchstone in a circular motion. Gah, I can't organize my thoughts and this is a horribly worded post, sorry.
Any help would be appreciated.
 
It's like this! Not my picture...

naniwa-nai0001-egaliseerblok-korrel24-d1.jpg


There are dedicated lapping stones you can buy (the one in the picture with the angled cuts) but whether or not you really need that depends on how precise you like to be about everything. Some guys measure both sides and lap the stone until it's accurate to within .001" everywhere. Some guys just rub two sharpening stones together until it looks flat. I saw a video where Murray Carter ("famous" sharpening guy) just focused his sharpening on the high spots to even the stone without wasting material. YMMV.
 
There are many options for flattening a benchstone. Go from cheap to expensive

1. Toss sand on fairly flat concrete, level the sand out. Rub in all directions/motions: back/forth/clock/counter-clock. Use motions to compensate for not true flat lapping surface.

2. 80 grit w&d sandpaper on flat wood/aluminum/glass/counter. Rub all directions.

3. Get a HF 2 Piece 4" x 24" 80 Grit Zirc Sanding Belts, fit the belt into a flat piece of 12" wood/aluminum/glass. Rub back&forth.
* or better with a norton blaze ceramic belt

4. DMT 2x6 or 3x8 X or XX. Rub back & forth

5. Atoma 140. Rub back & forth.

No need to rub in circular motion for 3, 4 and 5 but would be fine if you do. Except for 1. all others are great for major reprofiling blades.
 
I suspect you have the basic aluminum oxide combo stone, your best option is to wet the sidewalk and use a figure eight pattern.
 
You didn't specify just where you are, but keep in mind that depending upon your specific geographical location vis a vis the Equator, if choosing to use a circular motion, you would need to use either an anti-cyclonic or cyclonic directional pattern in keeping with the Earth's magnetic fields. That, or just scrub the sh$t outta the stone holding it flat on the cement sidewalk in front of your house. I've posted pictures here of Japanese knife sharpeners using stones that are dish out 1/2" in the center, looking more like salad bowls than sharpening stones. They still manage to get hair-splitting edges. Don't get yourself bogged down in minutia.


Stitchawl
 
Squashfan said:
Thanks for the good advice. Is it necessary to have a flat stone to get a sharp knife? No, it is not. But I think it will be easier to learn on a flat stone.
This is my stone: https://lansky.com/index.php/products/combostone-2-x-6-copy/
Click to expand...

Flattener abrasive need at least 3x larger than the stone abrasive, to be safe use concrete to flatten these low grit (below 300) stones.

edit: I do use my beat-up dmt X to flatten these low grit stones.
 
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So, should I use the rough concrete (IE: driveway) or the smooth concrete (front porch)? I think Bluntcut is saying rough but I want to be sure.
 
The rough, smooth concrete won't do much ;)
 
Squashfan said:
So, should I use the rough concrete (IE: driveway) or the smooth concrete (front porch)? I think Bluntcut is saying rough but I want to be sure.
Click to expand...

when possible use smooth & flat concrete (cement+sand kind, not cement only smooth surface) wet or dry lapping. otherwise do dry lapping on rough concrete - dust/powder will increase the grit (i.e. reduce roughness), this way it starts fast then slow down as dust accummulating, thus more refinement.

edit: ok, my response sort of redundant, at any rate it clarified concrete vs cement.
 
Do not lap dry!

You cannot effectively change the grit of a aluminum oxide stone, that's nonsense.
 
I lap all my stones dry.
For larger bench stones I use a dedicated flattener such as pictured above in post #2. I only flatten them when the dishing becomes rather pronounced. (i.e. you could slide a thick coin between the stone and a straight edge.) I bought the cheapest one I could find on the bottom shelf of an old hardware store. Think I paid about $5-$8 for it. Takes about 4-5 minutes to do and works perfectly.

For my EdgePro stones, I use a DMT course diamond bench stone to flatten them. I'm just careful not to use too much pressure against the diamond surface. Again, 4-5 minutes and the stones are straight again.


Stitchawl
 
I lap my stones always on wet level/ flat, rough concrete with good results. Then should it be a finer grit stone I take it to a finer grit lapping but no finer than 600 grit. Depending on the stone it takes me 15-30mins.. Watch the areas of pressure and take it in all directions. As you grind the grit gets finer. DM
 
I lap my stones using a tile rubbing stone I bought from Home Depot and some loose silicon carbide grit. I always use water, usually with some dishsoap to help it stick around longer between splashes. The grit breaks down as it goes. I get much better results using a loose grit and a fluid of some sort. Mineral oil works too, but is needlessly messy - water works fine.
 
Let me see if I have this right: I need smooth concrete. Put some water and sand on the smooth concrete and rub in a circular or figure 8 motion. Replenish sand and water often.

How does that sound?
 
Squashfan said:
Let me see if I have this right: I need smooth concrete. Put some water and sand on the smooth concrete and rub in a circular or figure 8 motion. Replenish sand and water often.

How does that sound?
Click to expand...

Very safe - full speed ahead! Nothing like a freshly lapped stone.
 
Smooth like a sidewalk, not like a garage floor.

Figure 8 will produce a more evenly ground surface, circular may induce a angled pitch on the stone.

Never heard of sand being used, I just use water.

This process is really simple, if it takes you more than 5 minutes your doing it wrong.
 
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