Quote Originally Posted by JimmyH-AD View Post

Just for kicks I drew a pencil grid on a Norton 4K and lapped it with the Norton. When the grid was gone I drew another grid and lapped it with the D8C. I did a few strokes and according to my grid the stone wasn't flat. So I finished with the diamond plate until the grid was gone.

Drew another grid and got onto it with the GDLP. Did a few strokes and according to the remainder of the grid the stone wasn't flat. So what did that prove? Well I don't know how to quantify the difference in the three results. I imagine any of the three were flat enough to accurately hone a razor relatively speaking and I'd like to think that the Shapton GDLP was the flattest of all.
Well, this leaves us with the the following question: Is the slurry is removing the grid lines before the hone is flat? To finish this test you would need to go back to the DMT after the Shapton and test again. The problem with flattening hones that break down into an abrasive slurry is that the slurry is acting on the remaining surface of the hone that is not yet truly flat. To be fair to the lapping device you are testing, you need to re-do the grid lines and lap the hone again to see how long it takes to remove the lines the second time. Once you can demonstrate that you can remove all grid lines within a few strokes with *any* of your lapping devices, you know that you have the hone as flat as you and that particular device can make it. Only then can you move on to another lapping device to see if there is any change in performance but even the grid line + number of strokes is NOT a proper way to measure the results. It takes a fairly involved setup to measure the flatness accurately. Let's say you take your hone to it's ultimate flatness with your Shapton, now you go back to the DMT and discover it's not removing all the grid lines evenly... Great, so which lap is out of flat?!?! We don't know as we've not measured against a *known* flat surface or taken the time to set up a rather complex measuring system. If we had done that, the next issue that we would have to quantify is your ability to operate the lapping plate with perfectly even pressure all around (you can't) so you need to methodically switch directions, turn the hone end for end etc. in hopes of trying to even such variables out. Again, it's not easy to measure these results and a thou here or there is trivial. And that is my point when someone starts babbling about micron accuracy... It's just not going to happen in real life and I realize I'm babbling away myself...... sorry.


Quote Originally Posted by JimmyH-AD View Post

When I lap a hone I do it in the kitchen sink under running water and I am not heavy handed. I hold the stone in my right hand and the plate in my left with the stone on top and all angled at 45 degrees. I let the weight of the stone do the cutting and flip the stone every so often end to end. I use an X motion as suggested on the Shapton website. When I am satisfied that all traces of the grid are gone I double check with my trusty Starrett 385 and I am good to go. I think I am doing an efficient job of it and would be grateful for any constructive criticism if it sounds like I am not.
You are doing a fine job for all practical purposes, the use of the Starrett makes me cringe a bit... I would hesitate to use such a delicate measuring tool to check something as abrasive as a hone. It won't take much to potentially damage the accurate surface of that straight edge, but it's the machinist in me that's cringing and only because good tools cost money and I hate to see them worn before their time.

By the way, a straight edge does not tell you if there is a wind/twist in your hone or if there is a crown along the centerline unless you measure both ways and diagonally and it would take two straight edges to sight any wind/twist in the surface and ultimately it's incapable of measuring to the claimed level of the GDLP but it sure as heck is good enough for your purpose which is making sure that you're not waaaay off in your flattening technique and that is all that matters.

Jimmy, thanks for posting your results, I hope you can find time to go back and recheck the grid line removal on the DMT after you are convinced you have a hone as flat as can be on the Shapton.

Quote Originally Posted by iron maiden
All of this sounds so darned complicated...think I'll stick with the coticules and thuringians for now.
That was not my intention, but I also didn't want anyone to pass up on the Shapton hones just because the sales dept. said you had to use their flattening hone or it won't work. And for the record, I'm still trying to determine if the 16K Shapton is as good as my Coticule as a touch up hone for me and my beard/face. So far, the Coticule is out front by a gnats whisker....

Regards

Kaptain "Couldn't think of anything witty to put here this time of the morning" Zero