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Reinis Kanders
07-22-2015, 7:32 PM
How flat should the new hard Arkansas stone be?
I bought a black 10"x3" stone from Natural Whetstone and it is quite off. It actually rocks in its box. Checking on a reference plate verified the twist of around .007 in.
This is a second stone from them with the same problem. According to company nobody else has problems and they are willing to take the stone back so that is good, but I am wandering if this is normal for a stone of this size. It almost seems like I got the same stone twice because wood box it came in was banged up in the same way as the first one and stone was out of flat in the same way. Maybe there are some systemic issues.
Best side of the stone has a 2.5" long and 1" wide high spot of about 4-5 thousands right in the center, I was thinking of trying to lap it out and then it would be fairly decent and I could keep it. Any suggestions on how to lap out the high spot without making more of a mess?

Thanks.
Jim Koepke
07-22-2015, 7:57 PM
I would put a small pencil mark on the box and on the stone might mark the high spot.

That way at least you would know if you go the same stone back.

Their stone saw may have a bad track that is causing the twist while cutting.

jtk
John Crawford
07-22-2015, 9:33 PM
I purchased a hard and soft ark from them. Neither were flat, but they were flattenable. After some work, I got them flat on almost all of the surface (they dropped off a bit at two corners, but this didn't prevent using them).

The hard ark is really hard (difficult to flatten).
Paul McGaha
07-22-2015, 9:37 PM
What would you use to flatten a really hard stone like that? Really course wet/dry sandpaper? Really course diamond plate?

PHM
Brian Holcombe
07-22-2015, 9:39 PM
The Shinden suita I bought was out wayyyy more than .007, so, I think that's probably a good candidate for lapping followed by use.
Reinis Kanders
07-22-2015, 11:33 PM
I purchased a hard and soft ark from them. Neither were flat, but they were flattenable. After some work, I got them flat on almost all of the surface (they dropped off a bit at two corners, but this didn't prevent using them).

The hard ark is really hard (difficult to flatten).

What did you use to flattten them? Diamonds? I have some DMT 8x3 stones. It seems that to selectively lap just a high spot with a big, but not big enough 8x3 stone I run a risk of actually making the hump more pronounced. I almost think I need to get one of these mini DMT 2.5x1 or 4x1 stones.
http://www.amazon.com/dp/B00004WFTB/
http://www.amazon.com/dp/B00IF57WZ8
bridger berdel
07-23-2015, 2:32 AM
Loose grit silicon carbide on the back of a granite tile.
Reinis Kanders
07-23-2015, 5:03 AM
Thanks everyone!

I used 80 grit Mirka gold psa on my reference plate. I got it down to .003 in corners and stone does not spin on reference plate anymore. Took about 90 minutes and 6 feet of the paper. Paper seems to cut very aggressively for about a minute or two and then it really slows down. I should be able to finish this in another session.
My plan is to charge the stone with some 1 micron diamond paste and have a fast finish stone.
george wilson
07-23-2015, 6:57 AM
Arkansas stones are SOFT compared to ceramic! I used to lay an old fashioned sandstone wheel down flat,and use water,and rub the Arkansas stone on it. The Arkansas was very quickly flattened. I also find Arkansas slip stones easy to modify with ceramic belts on my belt grinder.

Any piece of flat glass with a decent loose abrasive,such as silicon carbide on it will work also.