Thread: Lapping Plates

Last night I honed up a blade ready for a shave today. (In fact I have to test 3 razors today)

This morning I decided to re hone the blade because the HHT was not as good in the middle of the blade and there was no obvious reason for this.

Soon realised my 10k Chosera wasn't acting how it should. I normally use it then clean it with a Tomo Nagura.

I used a pencil and my DMT 325 to lap it but when I finished I thought , lets try now with the Shapton Diamond plate .

The stone was badly dished out yet the 325 was showing it as flat ..

The same story with my Escher.

I think I will only use the DMT 325 for slurry and only use the Shapton for lapping..

Just thought I'd warn you that your diamond plates or should I say worn diamond plates arnt as flat as you might think..

Or is the 325 just coarser than the Shapton? I know the my Atoma 1200 is finer than the Shapton

I don't think the issue is that the DMT isn't as flat as we think it is. One of my friends is an auto body tech. He saw me flattening stones with a figure 8, and pointed out that doing that would still allow stone particulate to focus near the center and it would never be perfectly flat. I can't recall what technique he told me to use, I was too entrenched in lapping the stone and just wanted it done. And the DMT gets the stone flatter that sand paper, and more than flat enough to hone a blade...

Now, look at your Shapton plate. See all those low spots that not only relive that suction effect but give swarf a place to accumulate that won't effect the plates cutting action - especially if the plate is on bottom and the stone riding atop it?

I would wager the Shapton is indeed getting your stone slightly more flat. But how flat does a razor stone need to be to get a razor sharp enough to shave? My face doesn't know the difference between the edge put on a blade by my still slightly convex Arkansas hone, which was lapped with a glass plate and loose grit SIC, and the dead flat one that came from Dan's and just got burnished. YMMV.

Originally Posted by Marshal

I don't think the issue is that the DMT isn't as flat as we think it is. One of my friends is an auto body tech. He saw me flattening stones with a figure 8, and pointed out that doing that would still allow stone particulate to focus near the center and it would never be perfectly flat. I can't recall what technique he told me to use, I was too entrenched in lapping the stone and just wanted it done. And the DMT gets the stone flatter that sand paper, and more than flat enough to hone a blade...

Now, look at your Shapton plate. See all those low spots that not only relive that suction effect but give swarf a place to accumulate that won't effect the plates cutting action - especially if the plate is on bottom and the stone riding atop it?

I would wager the Shapton is indeed getting your stone slightly more flat. But how flat does a razor stone need to be to get a razor sharp enough to shave? My face doesn't know the difference between the edge put on a blade by my still slightly convex Arkansas hone, which was lapped with a glass plate and loose grit SIC, and the dead flat one that came from Dan's and just got burnished. YMMV.

I lap under running water and do circles and x pattern to make sure particles do not get concentrated in the middle of the stone. Works well for me

For information, I have a couple DMT hones which rock corner to corner on flat surface. The amount of not flat raised corner is more than a postcard thickness. Another has enough curve to have worn the diamond off one end. Increased demand over the years may have been a factor leading to the problems. They are not sold as laps but as hones. The laps at stratospheric price they take the time.
~Richard

How are you judging, flatness, the removal of the pencil lines?

If so, yes, your slurry is washing off the pencil and the stone is not flat. The DLGP, Iwood and the CKTG plates have grid lines where slurry can build up and not affect the cut, but lapping under water is better and actually more efficient, because more of the diamonds are in contact with the stone.

It’s not the diamond plate, but technique. As said lap under running water, keep the plate clean and cutting fresh. Once the grid is removed completely, re-grid the stone and do 1 or 2 laps with light pressure under running water. Look at the stone.

If it is truly flat, most if not all, the grid would be removed.

Remember that to remove a low spot, all the rest of the stone face must be lowered to match the lowest spot on the stone. Often, we add more pressure to the low spot, but are just adding more slurry and washing off the pencil instead of lapping the stone flat.

There is a big difference in lapping a stone flat and doing a few figure eights to refresh a stone face.

I normally place everything in the bath with the shower running overhead..
Lapping back and fourth in a straight line and or circles.

Today was the first time I tried where I honed..

Yea, there has got to be a better and cheaper way to do this lapping that we need so badly to be done. My 325 is now.... worn out completely.

Originally Posted by Aerdvaark

Yea, there has got to be a better and cheaper way to do this lapping that we need so badly to be done. My 325 is now.... worn out completely.

Loose Sic grit and a flat plate maybe? Not so great for day to day hone maintenance, but decent for new stones, especally harder ones.

Yes, looks like I will need to be ordering some powders....

As a toolmaker/machinist, for things that are absolutely critical to make flat, I use a set of three cast iron or granite laps - always referenced and lapped true to each other. This obviously isn't necessary for flattening hones.

If you check ten diamond plates against each other in the manner described in the OP, (flattening the same stone twice by removing pencil grids with different diamond plates) you will likely find that none will show the exact same pattern. It doesn't take much difference for the pencil to be removed earlier in the center or the ends first.

Best way to check how far out of whack your plates are is to either use a straight edge and feeler gages or to lap two hones with the same diamond plate and then place them lapped sides together and check the gap between with feeler gage.