Shapton Pro Stones Questions

[Steve Friedman]

Jebediah,

I'm a little confused. Were the scratches there before you started with the Atoma or did they happen after you started using the Atoma?

Assuming they only occurred after you started using the Atoma, I agree that there must be something sharp and hard that's causing the scratches.

If there's no burr on the Atoma, I wonder if there's some random piece of loose grit from your earlier attempts that are still embedded in the surface of the stone. Or on your bench.

Here are some suggestions - in the order I would try them:

1. Until you have this figured out, I would do everything away from your bench to eliminate any possible contamination source. Find a sink and do this under running water or get a tub of water and do this underwater. Most importantly, far away from where you were using sandpaper and the Shapton grits.

2. Keep using the pencil hash marks. Hold the Atoma in one hand and the stone in the other. After 10 or 20 strokes, flip the stone only end to end. After another 10 or 20 strokes, flip the Atoma end to end. After another 10 or 20 strokes, switch hands and repeat the end to end flipping.

3. If the scratches are still there, but less, keep going. Hopefully you'll eventually get below the embedded grit.

4. If you're not flattening both sides of the stone, try flattening the other side and see if the scratches occur there as well. If you have been doing both sides and have scratches on both sides, try flattening the edges of the stones. If the scratches don't appear there as well, it's not the Atoma - it's grit something embedded in your stone.

5. Find someone with soft fingers (child? non-woodworking spouse?) and ask them to feel around the edges of the Atoma and see if they can fell a burr. If you don't have anyone around with soft fingers, use your lips to feel - don't rely on your calloused fingers to try to find this.

6. Wet the stone and get the soft fingered person (or your lips) to feel the surface of the stones to see if you can detect any loose grit on there.

7. Grab your plane blade or chisel with the shiniest edge and try to sharpen it on the 1500 stone. If there's a piece of grit embedded in the stone, you'll see the scratch on the blade.

That's all I have. Good luck.

Steve

[Daniel Rode]

I use diamond stones except for the final step where I use a 15k Shapton Pro. As a result, my process may be different but this is what I do.

To flatten the stone, I use my coarse diamond plate. I tend to work 1 stroke center (stones aligned), then 1 stroke each corner to corner. I can tell, if it's flat when the dark marks from the steel are all gone. I've seen some people mark the stone with a pencil, but I don't need to with the 15k stone.

No need to do it every time, I do it every 5-6 sharpenings.

I used to overthink sharpening. I thought I need precise angles, exact flatness, micro-aligned jigs and fixtures, etc. My tools became sharper when I stopped obsessing and let the simple act of sharpening be simple.

[Andrew Pitonyak]

I never really understood that whole loose grit thing to flatten stones... There was a discussion a while back with respect to using sandpaper to flatten stones. Stu mentioned a discussion with a guy who is President of a company that makes stones, and the gist was that the particles can embed into the stone from the sand paper...

So, why do these loose grit particles embed into the stone? Is it because they are not held in place as they are with the sandpaper? Note that I have indeed flattened stones using sandpaper and have not noticed the issue, but for the last few years I have used diamond stones to flatten.

[Steve Friedman]

I remember Stu's warnings about sandpaper flattening.

I have only used the SiC grit on two stones. I used it to flatten my Sigma 400 stone before I got an Atoma 140, but that stone is hard as a rock (pun intended) and will not let the grit in. I also used it to unclog my Sigma 120 because I don't think there's any other way to do that.

In both cases, I put the grit on those laminate sheets that Lee Valley sells for lapping so that the grit embedded in the laminate and didn't just roll around.

As messy as it is to flatten water stones with SiC grit, it's nothing compared to using the grit with a lapping plate and oil to try to flatten the bottom of plane sole. Now I know why sandpaper was invented.

Steve

[Brian Holcombe]

I only use the sandpaper and granite setup for flattening backs and setting bevels. I expect that it would not do well for the stones.

Using Tomo Nagura was the way to build slurry for a very long time, but it was recommended to me not to use that method either for the same reason that embedded grit causes issues with the finish on the blade. Some people burnish the stone with an identical stone for naturals but flattening with diamond plates seems to be the over-arching recommendation.

Having discarded the idea that the stone being super flat was important than revisiting the idea I have come to realize through trial and error that maintaining flatness on your stones is very helpful when you reach the finish stones and makes removing the wire edge much easier.

Mind you, I'm using mostly Japanese chisels at this point and so I make a full width bevel.

[Wilbur Pan]

The good news is that the scratches won’t effect how the Shaptons will sharpen your tools. Put it this way: if scratches in the surface was a problem, then there would be no way that these DMT diamond stones would work.



(I don’t like using DMT diamond stones for sharpening for a number of reasons, but this inverse-polka-dot pattern isn’t one of them. )

Where this would be a problem is if you used your Atoma plate on a tool, and a scratch was left in the tool from whatever was causing the scratch pattern on your Shaptons.

There has to be a particle or burr on the Atoma some place. The trick is how to find it. You could lightly brush over the surface with your fingertips. Another way to look is to take a piece of metal or a beater tool of some sort and use it to test the surface of the Atoma bit by bit until you find the area causing the problem. Or put the Atoma plate on one of your Shaptons and slowly move it in a circular pattern, and you should see a little squiggly circular scratch that will correspond to that area of the diamond plate.

Finally, a brute force solution is to jig up a plane blade that’s a bit beat up in a honing guide and just run over the surface hard and fast. Maybe you’ll find the problem spot, or knock off the burr in the process.

Alternatively, you could contact the store where you bought the Atoma from and get an exchange. In the meantime, your Shaptons are perfectly useable, even with the scratches.

[ian maybury]

Hi Jebediah: Looking closely at the photo of your diamond 'plate' it looks like (a) there's pieces torn away from the top LH and RH corners, and (b) that it's possibly showing wood underneath in those areas. Or is it some trick of persecutive, and the missing 'corners' are the sides?

The stock Atoma plate has a roughly 1/4in aluminium plate backer - this is what gives it its flatness. The diamond abrasive is a sheet of self adhesive foil stuck down on it. It's possible to buy a replacement foil on its own, it's a bit cheaper than the ready to use plate. (which has the foil stuck down on the aluminium backer plate)

Is it possible that you have somehow ended up buying a foil and not a ready to use plate? It's unlikely that 1/4in aluminium plate could be torn away. Also is it possible that you have stuck the foil down on a piece of ply or something similar? If so it's very unlikely that it could be flat. If so it's also quite possible that the torn edge is resulting in some raised diamond grits which could be causing the scratching you report.

Pardon me if you in fact have the proper aluminium plate. It that's what you have, and it's truly flat (checked really carefully with a reliable straight edge against the light) and free of stray grits, and you introduce nothing between it and the stone like large amounts of slurry, or loose grit, or dirt or something then short of rocking the diamond plate about by applying very uncontrolled and uneven pressure it's pretty tough not to end up with a flat stone. Scribbling pencil marks all over the surface of the stone is essential so that you know what is happening as you work.

It'd be a little more awkward if the stone was starting out badly humped, you would need to take care not to rock the diamond plate on it as you worked - but this should be pretty obvious if the pencil marks are clearing up too early from where they shouldn't i.e. from the low areas before the rest has been cut down to the same plane. You can check the stone with the same reliable straight edge and even mark the low areas - they should be the last to disappear......

As before/as the others - if you want to finish out to very fine grits on a stone/will need a very flat stone to get rid of the wire edge (and are not stropping or whatever) my inclination would be to stay well away from sandpaper on granite plates. it's perhaps not impossible, but it's tough to avoid some sort of rumpling in/a wave caused by pressure/displaced water running ahead of the stone and tending to cause a rounded edge. Also as the others, i'd not panic about a few length wise scratches anyway - not unless they are deep enough/in a direction where the edge may drop into them. A DMT type as Wilbur diamond plate is a good example of a sharpening surface that's like a cobbled street - but the point is that the abrasive mesh is all in the same plane...

[Jebediah Eckert]

Thanks for the responses. I'm going to give it a try again using some of the suggestions.

The Atoma is a regular plate with the 1/4" aluminum backing. The angle of the picture probably just looks strange. I had to crop or way down otherwise it wouldn't upload.

I'm off to search for the culprit grit or burr....