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I have found some used DMTs for pretty cheap and I was wondering how well they wore. Would it be worth $15 each for them? I have a choice of 120, 220, 325 and, 1200. the 1200 is in a smaller 6inch size and I have emailed the seller about the sizes of the other ones. Since a new DMT D8C is $54 I'm hoping these are usable for me. I can get multiples for cheap. 120 seems too rough but the other 3 grits interest me.
Well firstly we (per forum rules) cannot provide values. Secondly without photos it would be impossible to tell you how worn they are or whether they are too damaged to he usable.
120 is not too coarse for lapping and many of us get away with only lapping to that. Secondly I know where you saw these used DMT's but only you can make that choice on if it's worth it or not. For that price you're not out much if they aren't good but contact the seller and ask about refunds..
Worst case you have something to tape your sandpaper too..
I was asking less about the value and more about any experiance on how well they held up over extended periods of time and use. I guess I wasn't too clear on that.
The seller is a great guy to deal with so I'm sure something could be worked out if it was overly worn. I just wanted to know roughly how well they usually held up so I could base its lifespan with me on something. I've only ever heard of DMTs wearing out when people abuse them butnI wanted more people's opinions before I made a decision.Quote:
Originally Posted by S0LITARYS0LDIER
I used to abuse my lapping plate by lapping low grit sic with pressure, some diamonds ripped out but it still flattens wonderfully and will continue to do so for years.Quote:
Originally Posted by DduckyMark
Skipping over what is abuse and what is not, how long they last depends on what they're used for. It they were used to sharpen chisels, plane blades, lawnmower blades, machetes.....you get my drift...not indefinitely. Used properly to lap Naniwas or similar, they'd last a LONG time. Whether those grits are suitable for that purpose is outside of my expertise.
I have the 120 and have used it to lap very tough stones. I find it leaves too much scratching for my liking so I rarely use it anymore. Still would rather have it if in case I need it. The 325 is the workhorse for lapping stones, and for sharpening kitchen knives. Personally I would have no use for any plate but the 8".
I have a 600 that is only used for bevel correction on straights, and that rarely. A 1200 and a '8k' that I use for bevel setting on tougher steels like AS-34, S30V. So if all you want to do is flatten stones, go for the 120, and the 325. I don't sharpen tools, so depending on use, you might want all the guy has.
DMT recommends no lapping of hones on any plate finer than 325, and that under running water.
I've been flattening stones and occasionally sharpening kitchen knives with that 325 for 8 years. Still works, but not as well as it did years ago. I also have a different 325 that has been used alternately, so that may have contributed to the longevity of my D8C. :gl:
I do quite a bit of lapping. I use the DMT lapping plates. They stand up pretty well. They need a good scrub periodically with soft scrub and a stiff nail brush and they spring right back. Without having them in hand and trying to clean them or use them it is impossible to tell.
OK, I'll take the counterpoint.
Diamonds are hard, but the nickel holding them are not. Honing steel on the plates gradually wears out the diamonds but lapping hones wrong quickly can undercut the nickel, causing the release of the diamonds. There have been many threads about this exact thing happening, so it is not uncommon for these plates to get trashed by misuse. If you treat them well they will last for a long time, but you have to wonder how many of the used ones up for sale were treated well.
Caveat emptor.
Everybody compares their lapping plate to DMTs.
Why is that?
IMHO its because DMTs are the gold standard to which all others shoot for.
I have never met a DMT I didnt like, or find a use for.
Lastly we dont speak in monetary terms here.
To paraphrase Glenn, He still uses his DMT325 and it works well. He is one who uses his Often.
I heard that atoma plates were better than DMT's. I don't personally know if it is true as I only have an atoma.Quote:
Originally Posted by ultrasoundguy2003
You’re not going to be lapping a lot of stones with a 6 in plate. If you are lapping “a lot” of stones flat, a sub 325 plate will come in handy.
There are many good/great diamond plates out there, if money is an issue, see the many Diamond Plate threads.
But, for most… an 8 inch 325 DMT is a life time purchase, really they are not, that expensive.
I have both. Atoma works much faster both for lapping and honing. I cannot speak to their longevity as I have not lapped anywhere near as many hones with them in comparison to DMTs.Quote:
Originally Posted by edhewitt
I got an email back all the DMTs are the 8 inch except the 1200 which is 6inch. so they last a long time and a used purchase would work pretty well for me until I have more funds for a new one. Once I get a new one I'll have more then one which is never a bad thing.
No, crying…
It is true ........ IMHO.Quote:
Originally Posted by edhewitt
Well since the price is right I will get at least a 220 and a 325 and maybe a 1200. I don't think I would use the 120 and I'm not sure I will get the 1200 since I have a king 1k/6k already. If they have decent life left then I'll have saved some $ to get the Naniwa stones I wanted. If they are dead I'll email back and find out what can be done for me. at the very least I'll have good flat plates for my wet/dry sandpaper.
Atoma plates have better longevity and less stiction, they are better than DMTs for lapping stones. their arrangement of diamonds is better suited than just a random electroplate, in both cases (wear and clearance for swarf).Quote:
Originally Posted by edhewitt
They all get pretty slow pretty quick. The atomas settle in and stay they way they are at the slow point seemingly forever, and the duosharps, diasharps will wear through the nickel plate a little more easily.
DMT plastic versions are the only type I've had that are actually flat. Some of the diasharp versions can be out of whack a fair amount, so if they are diasharps and not duosharps, I'd let them go no matter what.
One comment about the nickel plate and what kills the stones - electroplated nickel is incredibly hard compared to something like steel. It doesn't get trashed in one shot, but coarse and aggressive abrasives will eventually wear through nickel plate. If you only use fine stones and medium stones (like a shapton 1000), it should take a very long time to have a problem with hone wear with any of the good diamond hones.
FWIW, if the topic is actually honing something (I don't use diamonds for razors) like a knife or a tool, the eze lap types are my favorite. They are not as pretty and well finished as the DMT and atoma, but they have a combination of mono and polycrystalline diamonds and have a better feel (and generally leave a better edge for the next sharpening step).
Ditto what DaveW says. The nickel plating thickness is a huge determinant of how well the diamonds stay embedded. On some plates I've seen it is way thinner than it should be IMO. Check these out:
https://scienceofsharp.wordpress.com...late-break-in/
https://scienceofsharp.wordpress.com...eak-in-part-2/
I'm glad to see those pictures at the bottom. One of the things that always comes up with tools when I suggest oilstones are optimal for someone who wants something that makes sense in the context of work is "well, diamond plates are better than oilstones". I noticed long ago that when you're using a DMT, you get odd random deep scratches, that cosmetically is annoying. For woodworking, I don't know if they really matter, but it always struck me as odd that even when you use a broken in DMT or other monocrystalline plate, you get some scratches that are difficult to remove - now I see why.Quote:
Originally Posted by eKretz
I don't get the same thing from a broken in eze lap, but even the ezelaps are pretty aggressive when they're new (DMTs are all mono crystalline and ezelaps are a combination of mono and poly).
I don't get the same thing from atoma, either, but the way the atoma diamonds are arranged in piles makes them fantastic for lapping stones, but a bit funny feeling for honing things in the larger particle sizes. Like honing on a zipper.
Do you see and consider those as an option
Thin Square Sheet Flat Diamond Stone | eBay
I have both DMT and cheap chinese plates and for hones lapping i dont see much diference i quality
I have inexpensive chinese plates, too, at one point someone was selling a milled chinese plate 8mm thick with two sides on it for $19 on ebay with a rubber base (the type of base that costs that much itself) and I have one of them and it's as good as a DMT diasharp, and close to flat (not perfect, but close enough).Quote:
Originally Posted by RusenBG
A well respected jeweler/machinist/instrument maker/tool maker/diemaker (he can make just about anything) that I know says those inexpensive chinese diamond sheets are the way to go if you have a lapping machine (he has some high dollar lapping machines). If you had a substrate to glue them to, I'm sure they'd be fine for hand honing, too.