Thread: DMT 8C Lapper not so flat - Any Thoughts?

The bottom really doesn't matter, but it certainly doesn't look flat on top. I'd contact either DMT or the place you bought it for a refund. IIRC, they guarantee flat within a rather small margin.

+1 - Contact DMT. Seems like you may have picked up one that missed their QC's scrutiny. Let us know what the outcome is!

It does look like the DMT should be returned and is not flat. I am not sure that what happened to the Naniwa's is from the lapping plate tough. The bow in the middle of these stones does not correspond to the plate being off, but to way too much pressure in the middles of these stones. I would have to see how you are rubbing the plate on the stone to accomplish what has happened here. Something doesn't make sense to me.

Have fun,

Lynn

DMT advertises they start with a steel plate true flat to 0.001".

So either you have a defective unit, or it's become warped with use. Was it ever subject to heat?

Along with others, I'd suggest you contact DMT about this.

I lap with no pressure whatsoever on the Naniwa stones, just the weight of the stones themselves, and I follow the procedure as in the wiki section if this website, and on the SRD DVD. I definitely do not put pressure on the plate, or the stones, and I keep it under running water to prevent too much slurry.

The DMT is brand new, and has not been subjected to any heat, or anything else. I just picked it up as a package in the mail 2 weeks ago, together with a second package. Both packages were delivered to me and nothing was damaged in the packages, so the fault must be from Dia Sharp's DMT production. Maybe I just got a "dud"....just my luck....or maybe I AM just a dud at this stone lapping business myself!

The DMT's centre is definitely higher than the sides, which, IMHO corresponds to what is happening to my Naniwa stones. The DMT's centre (which is higher) is making the centre of my Naniwa stones lower. Maybe I am getting this all wrong, but that is how I understand it. Please help me if I'm wrong..?

Originally Posted by Lynn

It does look like the DMT should be returned and is not flat. I am not sure that what happened to the Naniwa's is from the lapping plate tough. The bow in the middle of these stones does not correspond to the plate being off, but to way too much pressure in the middles of these stones. I would have to see how you are rubbing the plate on the stone to accomplish what has happened here. Something doesn't make sense to me.

Have fun,

Lynn

I went and checked some things out for you with my stuff...

Here is what I found..

Your DMT plate is way off, mine is dead flat
My Shapton GDLP is dead flat too
I use the Shapton GDLP to lap my Naniwas way less "sticktion"
Checking my stones when dry, showed some variance (light) between them
Checking the stones after they were wet for 5 minutes showed them to be dead straight...

My conclusions:
The binder expands and contracts a tiny bit...
Your DMT needs to be returned/exchanged

Originally Posted by gssixgun

My conclusions:
The binder expands and contracts a tiny bit...
Your DMT needs to be returned/exchanged

Thanks Glen, the binder contracting was also in the back of my mind, you may be dead right on this one. Maybe the stones "enlarge" ever so slightly when they are wet and being lapped, and then they actually "shrink" again when they are dry.

The fact that they are stuck to the plastic binder with some super epoxy, could possibly make the stones warp a slight bit as they change shape.... But who knows!

My naniwas are still slightly dished even when they are wet, so it still is a lapping problem with the DMT on top of that!

Another +1 on returning it, definately doesn't look flat.

Originally Posted by Leon

No way! This is not normal, IMHO.
I use the DMT 8C to lap the Naniwa's too and they're so flat that they "suck" when rubbing against each other. I can lift the upper naniwa and have the lower naniwa rise by itself just because of the lack of air between them.

+1, that's my experience and exactly how it should be. It may be a bugger to return, but that's your best bet at this stage.

Originally Posted by leadingedge

Here are a couple of photos of my new DMT8C I use to lap my Naniwa stones with. It turns out that the DMT is not very flat...
....snip....

As others commented contact DMT and or the place you purchased it.

I might note that while flat is ideal it is not necessary.
If all your hones have exactly the same uniform curve
you will end up with sharp edges.

To that end I went for years honing my two razors with a Belgian Coticule
and never lapped it flat. My razors and the hone matched up
and the edge was consistently fine.... Later I added other razors and
other hone at which time lapping to flat made sense. The result was I
did have to reset the bevel on my old razors and revisit my sharpening.

If I was a honemaster flat would be a requirement because there is no
way that a customer could match anything other than flat for their
maintenance honing.

i.e. if you are stuck in a corner of the world where getting a replacement
is impossible do not despair.

As for the shape of your hones they do not look as if they match
your DMT. If your DMT is shorter than your hone use some care
because it is easy to cup the hone. I am 'cheep' and have a short
DMT but I only use it to touch up my hones. I use a sheet of 3M
wet/dry to lap my hones flat. Pencil marks let me quickly see the
high spots that I knock down with the DMT then the final surface
is done with a second set of marks and the 3M paper on a flat
granite tile. Running water helps a lot.

Lapping for an individual shaver is not a common requiremen.
I have an extra coarse DMT and a fine DMT. I use the fine
DMT to lightly refresh the surface of my hones and also set a bevel
on troubled eBray purchases. The extra coarse DMT I got to
tidy up my C12K, badly chipped edges and whatnot.