Thread: DMT stone lapping

Originally Posted by K37

I have a few of DMT stones in various grits and find the 325 the most versatile between my hand plane blades, spokeshaves, knives, axes, their hones and now straight razor hones. I personally wouldn't go below a 8x3 for lapping because you won't get it flat as well...ideally the lapping plate should be bigger than the item being lapped but not completely necessary...you could use a 6 inch. The stand isn't necessary although convenient.

Hmm, my eight year old lawnmower has never had it's blades sharpened. Could I use it for that?

Originally Posted by RADisorder

Hmm, my eight year old lawnmower has never had it's blades sharpened. Could I use it for that?

It would love you for that!

Originally Posted by PierreR

I see DMT has a dedicated lapping plate for hones. Quite a few hold the DMT 325 in high esteem. Has any one used the lapping plate? Its a pricy bugger, and I can't seem to find a "grit" rating on it... But I am curious, and am wondering how they fair side by side on synthetics and naturals.

if you want to get a more expensive lapping plate you could go for the shapton DGLP I'm pretty sure people say good things about those I just don't see the point when a DMT 325 does the job

Originally Posted by gssixgun

The DMT 325 is the Highest grit plate that can be used safely for lapping, using the higher ones runs the risk of undercutting the Diamonds

What is this 'undercutting' of which you speak?

For lapping I use a DMT Duosharp, 325 one side, 600 the other. The 325 I use for initial lapping while the 600 I use for touch ups and on my finishers. My thought was that the 600 side would be less aggressive and leave shallower scratches which would be better, especially with regard to the finishers. And so far it seems to have worked very well. Living on borrowed time, flawed thinking?

I have the DMT Dia-flat lapping plate, which I believe Pierre is referring to. I use it to lap my Zulu Grey hones as part of my process, and so mine has seen quite a good deal of lapping. When I first got it, it was super coarse, as can be expected, and it certainly did feel like 120/160grit. But, after 'knocking it in' it has smoothed out quite a bit.

I like it for a few reasons: It's massive, easily bigger than any of my hones and so evenly lapping a hone is quite simple and comfortable. I also like the heft of it - it's a thick plate of steel, so when set on a thin rubber mat on a hard counter, it isn't going anywhere and I like that stability. The diamonds are also bonded to the plate in some proprietary way, I don't know the science, but I do know that I can easily see this plate lasting a seriously long time. It can also lap everything - hard stones like Arkansas's and soft ones like the Norton 8K..

The way I use mine is first apply a medium pressure with constant water - I have mine on a thin rubber mat set on a granite block, and this is semi-submerged in a large basin of water, so that the waterline is just breaking on the DMT plate. This way the movement of lapping allows water to always be flushing the plate which keeps it working well. So medium pressure on a 'well worn' lapping plate lets you quickly cut down even the most dished of hones, and honestly it leaves what I was say looks more like 220grit scratches in the stone, not 120 or 160..

Then what I do is lighten the pressure considerably, so I'm just using the weight of the stone I'm lapping on the DMT and I alternate back and forth movements with broad circular movements.. Do this for a little while and all the '220' grit scratches are gone and the stone is left more than acceptably smooth to hone with. I would say with the light pressure and the circular movements you can easily create what looks and feels like a 400/600 grit finish. So for me this is sort of a do-it-all lapping device. You can easily cut down very rough rock, and you can create an acceptably smooth honing finish all with one lapping plate.

I would say though, that it probably is more suited to someone tackling a bunch of hones on a continual basis, and so it's more of an industrial/professional tool - certainly not something casual straight razor users need to acquire. But, I felt I should mention that it can finish coarse and smooth if used correctly with the appropriate technique.

- Mike

Originally Posted by RADisorder

Hmm, my eight year old lawnmower has never had it's blades sharpened. Could I use it for that?

A file works just as well and quite a bit cheaper too.

Bob

Originally Posted by RADisorder

Hmm, my eight year old lawnmower has never had it's blades sharpened. Could I use it for that?

I guess you could; I use my grinder for that. I don't sharpen with a 325. I repair nicks in my woodworking blades and remove metal to reestablish the original bevel when my secondary bevel gets to large. If you want versatility then a 325 is a good one.

Thanks guys. I found the DMT 325 for under $60 so I will go for that one.

@Michael Thanks for the explanation, I appreciate it. I won't need it anywhere near the industrial level, so I will conserve my pennies. Nice to hear how you do the Zulus!!

Does the one with the dots work? It looks like the dots are recessed to collect debris. Would this grater type chew up hones?