Saturday, March 1, 2014

Fresh and fast..... flatten an India oilstone quicker than I thought possible

I am trying REAL hard to wean myself off of my diamond sharpening stone dependency. They are fast, but they are also expensive and can wear out at an alarmingly quick rate, when used with any frequency. A light touch can help prolong their life but there is more to it then that.

I need a seriously flat stone for lapping and none of the stones that I have tried are even close to truly flat. DMT offers the dia-flat line, but then they also say that their other stones are flat too, which has not been my experience. And their grit seems to wear erratically. And my stone is delaminating. And It seems to leave the occasional REALLY deep scratch that takes forever to bring out...... I'm not feeling too good about DMT right now.

Eze-lap? WAY not-flat (too bad, they are otherwise very good). The Tsuboman Atoma seems to be the gold standard, but I am loath to drop $100 on a consumable item, just in the name of convenience.

I plan to start using loose diamond grit on a lapping plate. I use loose grit for lapping stones and it is so much faster than any kind of fixed abrasive that it doesn't bear comparison. AND you actually make surfaces flat, as opposed to domed, cupped, and twisted. That should be good for flattening blade backs, but what about the bevels?

I got a HUGE 11.5 inch India/carborundum dual grit stone from my friend Brandon, but as with nearly all used stones it required a fair bit of flattening. You can do this with sandpaper on glass, but buy a lot of paper and give yourself a month to finish. It is SLOW! Beware of falling standards.... You can use a diamond stone, but ruining a $100 stone to save a $40 stone........ my math skills are poor, but not THAT poor.

This is super fast AND super cheap! This stone was dished and had a central groove on both faces, not badly, but something to be aware of. The main issue was that it was SLOW(!!), probably glazed, so using differential use/wear to get it back to a flat condition wasn't gonna happen. This DOES work.

  • A FLAT ceramic tile ($1, bring a straight edge. This was the flattest out of the 5 that I looked at.)
  • Sandblast grit (Free, from my friendly building supply store. The bags leak a bit or get ripped, so there is often some on the floor. I grabbed both coarse and fine.)
  • A stone that needs flattening

I used the BOTTOM of the tile.

The carborundum side wasn't too photogenic, but it was SUPER fast and proved "proof-of-concept".

Make SURE that the bottom of the tile is as flat as you want your stone to be. I tried this without the grit and the results were underwhelming. The grit is key. It is only quartz sand, but it makes all the difference. Just sprinkle some around, add a tiny bit of water, and start rubbing.

T=0 seconds
I used the coarse grit for the carborundum side, but for some reason it didn't work well on the India side.

The fine grit worked great. It breaks down quickly, so just add more as needed. I used about 1/4 cup total. A $12 bag would be a lifetime supply (for you and your 300 SharpeNerd™ friends...).

This is the fine grit....

T=60 seconds

T=3 minutes or so
As the stone approaches flatness, the surface area increases and progress slows. Maintain your high standards! Flat is good.... and makes sharpening MUCH easier. You might have to apply more pressure to one end or the other. Use a straight edge.

T=8 minutes continuous ( 45 minutes if you count sprinkling, washing, squinting, and clicking).
This was used with oil, so there is some residual staining.

F is for flatness.... It's good enough for me......

You might not want to wear your best clothes, though....

Results? I've got a really hard laminated chip-breaker that need sharpening....

It feels like a completely different stone. Before, the blade just skated around and not much metal was removed. Now the stone makes a gawd-awful grinding crunch...... Obviously the stone was glazed with old swarf and grit filling the pores. Not anymore!

I am using water, not oil.

This is good, but the feel of the stone is...... unpleasant. 

My good friend ODC to the rescue.....

The ODC fills the pores without clogging them and smooths the action by forming a slurry. 

**This seems to be an important point**

In use, as the blade extends over the edge of the stone, it can grab slightly, digging in and marring the blade. This will prevent you from using the whole surface of the stone, which is what will eventually cause dishing, grooving, etc. My theoretical goal is to never NEED to flatten a stone, so I use every part of the stone and frequently check for high/low spots. The ODC  cushions or buffers the action by making slurry and reduced the feeling of "dragging". The blade is easier to control, and the whole surface can be used effectively. It also quiets the sound a bit, too (no small thing!).

India side.... Better than it was, but still slow. It feels like the metal is being scraped away, not cleanly sheared. This is partly due to using water instead of oil.

Pretty light....not much swarf, is there?

With the ODC?

Color! Again, a different beast.

I initially tried the coarsest W/D I could get, 220 grit, 2 sheets...... 30 minutes of work yielded little on the carborundum side, and even less on the India. Using loose grit quartz sand on an inverted ceramic tile, I flattened the carborundum side in maybe 2 minutes, the India in 8 minutes.

Physically the work is easier, too, at least as these things go. Sandpaper has a high coefficient of friction, whereas this is like rolling around on..... sand. Sandpaper tears. Sandpaper is expensive. This cost me a whole $1 for the tile (and the tile is virtually unaffected. Since I was using the back, the face is still good. I could even use it as a... tile!).

This combo-stone isn't as fast as diamond, but might actually work for me. With the ODC nagura.

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Like all of us, I am figuring this out as I go, so when you see something that is incorrect or flat out wrong (and you will!), let me know. This is a learning process. Real people and names, please. Constructive comments and questions are very welcome, but hate speak/politics are not! Life (get one!) is too short.

Thanks, Jason