All of these sharpening stones that I have been making, every one needs to be flattened. I have been doing that using various combinations of loose abrasive grit on a flat (ish) substrate. This has proved to be so much faster than, say, sandpaper on a flat surface, that I can't imagine ever using the sandpaper method again. Loose grit is faster AND gets the surface flatter, win-win.
For tools, the choice is not as simple. I have piles of old tools and most of them require fairly substantial reworking. This means removing lots of metal, and even *I* get tired of grinding away for hours on end, at least if the time/work curve feels painfully flat. I do use power tools, grinders and the like, but I prefer handwork, IF the T/W curve is reasonable.
I am going to be trying loose diamond grit on a lapping plate, but for now, I just want to make some surfaces flat. I have been using a flat granite tile and valve grinding compound....
So. Diamond stones. The hand sharpener's Crack cocaine... And they are flat, right?
Two stones, a DMT duo-sharp and an Eze-lap #600 grit.
The two stones use different types of diamond grit. The DMT uses a mono-crystalline diamond abrasive that they say is better/more expensive/higher quality/longer lasting etc. The DMT does leave a nice, even scratch pattern, at least on the #600 side.
The Eze-lap #600 uses poly-crystalline diamonds and though old and worn, still is MUCH faster than the DMT, although the finish isn't quite as fine. This is consistent with other people's findings. You can read a bit about the mono/poly debate in various venues, written by people with WAY more experience the I.
Like this one....
The consensus is that mono starts fast, wears out fast, and produces occasional large scratches. They are more expensive, too. Sounds familiar. My $8 set of (not so)crappy Chinese diamond stones are still working fine, even though they get abused on a daily basis. They are most likely poly diamonds. Seriously, just today I did the rough shaping of an old kanna blade, worked on the initial flattening a MF'ing hard potential sharpening stone, chamfered the edges on another stone, sharpened an old Japanese ax, and (finally!) worked a bit on flattening a cast iron lapping plate.
I am going to send my DMT in for evaluation. I'll let you know how that goes. Today, I would give 5 DMT's for 1 old Eze-lap. Maybe 7. Probably not 10, though. I mean, it DOES still work. I have read that some of their other products are more consistent in the lateral plane ie: Dia-flat lapping plate @.0005/inch.
Kinda spendy, though.