DMT 8C Lapper not so flat - Any Thoughts?

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...

OK, I'm not a master lapper yet, but do you guys think this is normal, or should I look into it? Look at the right side of the photo, I checked it on 3 different glass panels with the same result, the middle of the DMT is slightly higher than the sides. I push down slightly on the left side, then the right side lifts up, and vice versa.

Attachment 48235


And here is what this DMT did to my Naniwas. You can see the light coming through the centre when the Naniwa stones are face to face. They are all now slightly dished by the DMT8C.

My Naniwa 8K & 12K
Attachment 48236

My Naniwa 1K & 5K
Attachment 48237

Just to be sure, if you have not put the plate against a straight edge, try that first to make sure it is the plate.

Send it back to DMT. It would not hurt to give them a call. I have many DMT products and they will stand behind their products.

If this is not normal, I will consider sending it back, but I do not live in the USA, so it is a nightmare sending stuff back and forth.

If you guys think this DMT is normal, I will continue using it.

Maybe DMT's tolerances are just so far off perfect that this is deemed "normal"? Any ideas?

I don't have a straight edge measurer, so the best I can use would be perfectly flat glass, this is why I checked it on 3 different glass panels, on 3 different surfaces as well, just to be sure. All the same result...

Quote:

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Originally Posted by leadingedge

If you guys think this DMT is normal, I will continue using it.

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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.

This makes me wondering: How do you LAP a LAPPING stone? With a even more coarser stone? What guarantees that the lapping stones are perfectly flat?

These diamond plates can not be lapped - they are diamonds bonded to a metal plate. It is the plate that is dished if it is untrue - lapping it would damage it

How new is the plate ? Did you take a plane blade or something and rub it out ? I don't have planes so I used the shank of a heavy 12" screw driver for mine. What I'm getting at is there may be high spots on the diamond coating. Probably not as high as what you've got there but it might help.

Flip the plate to the smooth side and check it with a straight edge. It will be no less flat on the smooth side than it is on the diamond side, and it is easier to see if the plate itself is flat, and if not how far out it is.

I've returned two diamond plates to Dia-Sharp here. A 325 D8C and a 1200 D8EF. They agreed with me that the D8C was not flat within their specifications but said that the D8F was within their tolerances. It took a month or so but I eventually received a new D8C and they returned my same D8EF to me.

So number one, you have to return it to Dia-Sharp for a replacement. They will replace it if, once they test it, the plate is not within the tolerance they mfg them at. If it is within their tolerances they will return it as is. You should get with them via email. :gl:

Thanks guys, will try and find some way of measuring the DMT again, but I am pretty sure that it is not flat. The result is shown in my Naniwa stones pictures.

I lap extremely lightly with only the weight of the stone lying on the DMT, so it takes forever to do, and I keep running water on the lapping, and swivel the Naniwa around 180 degrees every few minutes, just to be sure that all areas are covered by slight unevenness in the DMT, but this still does not work.

This is dissapointing and unfortunate, and I will try and find a way to sort this mess out; I don't live in the USA, so sending stuff back and forth with numerous phone calls will probably be more expensive than I can imagine.

I guess the way to go here would be just to bite the bullet and go for the Shapton DGLP.... That is if nobody has had any problems with them...?

Anyone?

It is also possible that while lapping you are spending more time on the middle of your hones than the edges. As already mentioned, checking the DMT for flatness would be a good idea.

A non-flat DMT is definitely unusual. I don't think I've ever heard of one up till now, and it seems lots of people use them. Maybe you got unlucky. You could try a DGLP, but I highly doubt a second DMT would be non-flat, and it's a much less expensive "experiment."

I do move the stones around to avoid lapping the centre too much, so I don't think that is the case. Every minute or so while making small circles, I lap towards the sides, and back to the centre. I also make sure that there is not too much slurry to affect the centre of the stones, so I doubt if this is the case...

It seems that I am certainly not the only one finding a DMT that is not flat. Got some info from a PM converation with another highly respected member that he has had more that his share of DMT's that is not flat...

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Originally Posted by holli4pirating

It is also possible that while lapping you are spending more time on the middle of your hones than the edges. As already mentioned, checking the DMT for flatness would be a good idea.

A non-flat DMT is definitely unusual. I don't think I've ever heard of one up till now, and it seems lots of people use them. Maybe you got unlucky. You could try a DGLP, but I highly doubt a second DMT would be non-flat, and it's a much less expensive "experiment."

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Well, here is the verdict. The DMT8C I have is definitely NOT straight. I checked the top of the plate, and the bottom of the plate, and just to be sure, I used 2 different Stainless steel edges. Can this be used for lapping guys? Check out the photos below:

Bottom of the DMT8C Plate:
Attachment 48284

Top of it, edge #1 (Edge rocks from side to side, as the centre is higher)
Attachment 48285

Top of it, edge #2
Attachment 48286

Bugger.

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! :rofl2:

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..?

Quote:

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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

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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

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Originally Posted by gssixgun

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

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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! :boohoo:

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.

Quote:

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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.

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+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.

Quote:

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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....

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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.

Update on what is up for those who wanted to know.

My new DMT8C is on the way, the old one is confirmed a bit "off".

The guys from SRD, as always, were great about the whole thing, and a heck of a lot of help to sort it out.

For all of their help, I decided to buy another lapper from them....you guessed it - a Shapton DGLP!

So, now I will have a hard-core lapper DMT and the best of the best DGLP as well. Probably a huge over-kill, but I guess that is what HAD does to you!

While I have no lapping stone, I lapped my Naniwa 1K and 5K with 220 grit sandpaper on top of a spare large smooth floor tile I have at home, and they came out flatter than ever.

I can get them to suck onto each other when I have a layer of water inbetween them, so they are far better off after a sandpaper lapping. Took a bit of time, but it worked just fine.

Question:

What type of stones do you guys lap with the DGLP, and what type do you lap with the DMT8C?

I'm considering using my DMT8C as a lapper for my Lansky 120 grit knife stone as well, but I don't know if it will be OK....maybe if I lap really lightly?

Thanks!