Flattening Arkansas stone

J

JKLnHYD

Joined
Apr 14, 2014
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50
I have a 10" soft Arkansas stone that has a slight low spot, almost invisible, near one end. I can still feel it though, and I'm worried I might damage a blade edge running into it. I was wondering if something like a fine diamond credit card hone could be used to smooth it back out.
 
Arks are pretty hard on diamond stones. I'd recommend lapping it with a flat piece of glass or granite and loose silicon carbide abrasive. I use a cast iron lap myself.
 
Thanks. And thanks for the quick reply. Gotta love how quick you get a concise answer on this forum.
Edit
I kind of figured a diamond stone would be pretty much sacrificial in that capacity. Glad to get alternate suggestions.
 
You can use silicon carbide wet/dry sandpaper on a hard surface.
 
Make sure to use plenty of water and a loose grit. Sidewalk, coarse grit wet/dry sandpaper, etc. I use a loose 120 grit silicon carbide grit and a cheap combination stone with plenty of water and some dish soap.
 
Yes, I always heard a relatively flat concrete floor, and dust from a surface grinder were pretty good ways to flatten stones at work. At home, I think doing about the same on a granite surface plate would be better and mo flatter.
 
Oh yeah. I was a machinist for 20 years until my back gave out. I have a nice cast iron lapping plate about 13" x 8" that I brought in to the shop and surface ground to reflatten it - after being used in a toolmaking shop for a while it had about a .002" hollow in the middle. I can flatten just about anything to within less than .001" using loose silicon carbide grit - and the nice thing about doing it with loose grit on a lapping plate is you don't ever have to worry about the cutting speed slowing down - you just sprinkle on a 1/4 teaspoon more grit and you're good to go just like the first time you ever used it. I've flattened granite plates, float glass plates, Arkansas stones, all my waterstones, a Spyderco UF bench stone, all sorts of stuff - and I've only used the first side (mine's double sided). Checked it the other day after about a couple of months use and still can't get a .001" feeler gage under a precision straightedge anywhere. It's important to try to use the surface evenly so you keep it flat as long as possible if you want to use it much. Some folks try a sheet of wet/dry on top of their lap or granite plate and use loose grit on top of that to try to prevent wearing the lap but I've found that just using the lap works great and gets things quite a bit flatter also. I can lap two items and put the lapped sides together and can't see any light through the interface. Using a sheet of wet/dry tends to roll the end up a little and give a surface that's pretty flat in the middle but a tad convex around the periphery.
 
Just thinking about HYD's problem, a small plate would give bad results and a large grinding surface would give good results.
He has to take down the rest of the stone to the low end. Just poorly finished. Whereas most of us normally need to take down the ends of the stone to match the dip in the middle. Uneven pressure resulting from a strong arm could give poor results. So, rub a little and check it. Rub some more and check it. Making sure to use even pressure. Plus, before starting this project take a black marker and mark diagonal lines across the stone. This gives a reference as to how progress is going. DM
 
eKretz said:
Oh yeah. I was a machinist for 20 years until my back gave out. I have a nice cast iron lapping plate about 13" x 8" that I brought in to the shop and surface ground to reflatten it - after being used in a toolmaking shop for a while it had about a .002" hollow in the middle. I can flatten just about anything to within less than .001" using loose silicon carbide grit - and the nice thing about doing it with loose grit on a lapping plate is you don't ever have to worry about the cutting speed slowing down - you just sprinkle on a 1/4 teaspoon more grit and you're good to go just like the first time you ever used it. I've flattened granite plates, float glass plates, Arkansas stones, all my waterstones, a Spyderco UF bench stone, all sorts of stuff - and I've only used the first side (mine's double sided). Checked it the other day after about a couple of months use and still can't get a .001" feeler gage under a precision straightedge anywhere. It's important to try to use the surface evenly so you keep it flat as long as possible if you want to use it much. Some folks try a sheet of wet/dry on top of their lap or granite plate and use loose grit on top of that to try to prevent wearing the lap but I've found that just using the lap works great and gets things quite a bit flatter also. I can lap two items and put the lapped sides together and can't see any light through the interface. Using a sheet of wet/dry tends to roll the end up a little and give a surface that's pretty flat in the middle but a tad convex around the periphery.
Click to expand...

Interesting post eKretz - do you use water with this and if yes how much?
 
Andy, yes I do use water, just not straight water. I mix a ketchup style squirt bottle full of Dawn dish detergent and reverse osmosis water - about 1/8" of dish soap in the bottom of a 2" diameter bottle that's around 6" tall - the rest water. When I start lapping from a clean plate, I sprinkle on 1/2 teaspoon of the abrasive I want to use, then shake up the soapy water bottle and squirt just enough to wet the surface of the lap a bit. Maybe a couple ounces of fluid. I then spread the mix with my hand a bit to get even-ish coverage and start to gently lap until the grit has spread pretty evenly. After that I either bear down with some pressure if I have a long way to go on something tough or just use the weight of the item I'm lapping if it's nearly flat. To refresh, I add 1/4 teaspoon more grit when it breaks down (silicon carbide will continually break down finer and finer as you lap) and give a few squirts more soapy water. I find it best to keep the lap fairly wet, so if it seems to be drying out before I'm ready to add more grit I'll give it a few squirts of the soapy water now and then. Final lapping is always done with just the weight of the item being lapped - sometimes I'll even lift a little so there's hardly any down pressure depending on the weight of the item in question. After lapping I always clean the lap completely and scrub it with a plastic scrub brush and hot water, then dry it and blast it with aerosol silicone spray. Next lapping session I blast it with a hot water rinse and start as mentioned earlier. It's kept the rust at bay quite well.
 
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