Monocrystaline Diamonds ??

Flatness of Diamond Stones

Steve Elliott

>Over the years I've bought at least half a dozen diamond stones. Every one was out of flat, despite my attempts to choose flat ones. The coarse ones usually were high in the middle, which made them useful for quick stock removal but not good enough to lap things flat. The finer grit stones tended to be closer to flat, but not nearly as flat as I can get my waterstones.

Re: Flatness of Diamond Stones

Christopher Schwarz

>Maybe my standards of flatness are different, but I've never had a problem with a DMT (the only brand we use) being unsuitable for woodworking. I check them with a 24" Starrett straightedge and feeler gauges. I use the diamond stone to true everything else.

Chris

Just checked four stones

Steve Elliott

>Just now I checked three black DMT stones (extra coarse), and a double-sided red/green DMT. Using a granite surface plate and feeler gauges, I found that two of the DMT black stones were high in the center by .005 in the long dimension and by .0015 from side to side. The third black stone was much better, being high by .002 in length and flat in width. The oldest stones seemed to be the least flat.

The two-sided DMT was flat as far as I could detect using feeler gauges. In use, I've found that after lapping a blade back on the red side and then progressing to the greed side, the pattern of the polish on the blade shows that the two sides aren't both equally flat. I've stopped using this stone for lapping backs because waterstones seem to work better for me. Because the waterstones have all been flattened on the same surface plate, the finer stones abrade the whole blade back when it comes off the next coarser stone.

Using a diamond stone to true other surfaces gives the same result. Waterstones flattened on a diamond stone will all have the same shape, so progressing up through the grits will go quicker than if each stone has its own subtle difference in shape, either dished or crowned.

For most sharpening purposes, a stone with a crown of a few thousandths in the long dimension will work fine, but a crown across the width can result in a blade with corners that project farther than the center. For flattening the sole of a plane, the .005 crown would be a problem.

Re: Just checked four stones

Dave (Arlington, VA)

>Thanks, Steve -

Are you flattening your waterstones with sandpaper on your granite surface plate - or by some other means.

I did go on the DMT website and while they did mention their stones were flat - they didn't reference any standard or how much deviation could be expected over any given length.

Again, thanks.

Dave

Re: Flatness of Diamond Stones

Dave (Arlington, VA)

>Hi Christopher -

I appreciate the report. I know you flattening quite a few blades! Truing other stones is what I was considering the DMT for, but I began to get uneasy when I couldn't find anything to show that they were indeed flat.

I guess I could take in my 6" Starrett straightedge (the best I have), but I thought I'd feel a bit self-conscious standing in the store holding up one of their stones to the light to see if I could find any light peeking out from between my straightedge and one of the surfaces of the stone.

Again, thanks!

Dave

Japan Woodworker describes the DMTs as being...

John Truxell-Svenson (jvs)

>...within 1/1000" across the long axis, but it is strange that DMT does not list a spec on their site. As has been pointed out before, that sort of wording doesn't necessarily mean that there is a maximum deviation on and point of less than .001" from a flat plane; it could be stretched to mean that there is a spot on one end that is 1/2" high and on the other .499" low.... :)

Another option (also in the JW catalog; I'm sure other places as well) is 3M's PSA/polyester backed diamond sheets on a flat substrate like a reference plate--these would be about as flat as the substrate itself. Of course, given the cost of any diamond "stones," the Harris system mentioned a few days ago looks pretty good, too.




/jvs

Re: Flatness of Diamond Stones

Fred Krow

>Dave,

I did that flatness testing Saturday at the local Woodcraft store. Two employees became interested and helped out.

Note: the specs. on their 24 precision straightedge is 0.002" over the length of 24". The two I checked were way out of straight wrt each other.

The Woodcraft brand 12" metal scales were not even close. The published specs apparently are not held in final inspection by the manufacturers.

My next project is to have a machine shop take a 0.100 x 24" bar of stainless steel and grind the edges straight on a surface grinder.

Regards,

Fred Krow

Re: Flatness of Diamond Stones

Pam Niedermayer - Austin, TX

>I wouldn't feel bashful about this at all, didn't bother me a bit to check their small squares via the draw-a-line-and-flip test.

Pam

Re: Just checked four stones

Christopher Schwarz

>I've never been able to get a feeler gauge under a DuoSharp (the two-sided stones). I've got four or five of them in our shop.

And though I may get a slightly different scratch pattern between grits on the DuoSharp, I have to remove those scratches with a polishing stone anyway, so I don't consider that an issue.

The way I see it is that the DMTs are flatter than anything else in my shop. All my other sharpening mediums (waterstones, oilstones) go out of flat the moment I start using them.

Further on that point, I'm not looking for a perfectly square edge on my plane blades (about half of my sharpening). I camber the irons for my smoothing planes, jointer and jack. So utter flatness isn't a goal.

And as to sandpaper and its flatness, keep in mind that it's not just the glass or granite surface you are working on, it's also the manufacturing tolerances of the paper (generally very good, but not always). And, in my opinion, the paper tends to load faster than a diamond medium, which changes the paper's cutting characteristics.

I'm not trying to ding anyone for trying to achieve accuracy. We all have different expectations for our tools and our work. For me, the DMTs are more than accurate for my woodworking, and I feel I work to a high standard.

Chris

Re: Monocrystaline Diamonds ??

Steve Knight

>the Norton stones are about the best consumer stones out there. But diamond stones wear pretty fast in a sharpening steel capacity. Myself I never found them cost effective.

If you want the flattest stone Shapton makes a stone that is flat to a 4000�s of a mm. It is not like normal diamond stones. The stones are full bedded then ground flat. But at about 400.00 it is not cheap.

same experience

Bill Tindall, E. TN

>Diamond stones wear out too fast in coarse grits, at least in my hands. Much cheaper to get cast iron plate that has been ground flat and charge it with diamond powder. $20 worth of powder looks like it will last me years.

Flattening waterstones

Steve Elliott

>I flatten my waterstones using wet/dry sandpaper on a granite surface plate. I've found that the A weight paper gives the flattest surface, but for removing material more quickly I use 150x paper in the heavier C weight. The result is a very slight crown on the stone, which is OK on the coarser stones. (Think of the concave area on the back of a Japanese chisel and you'll know why.)

Flattening the waterstone is a part of every sharpening session for me. Even the Shapton stones that wear much less quickly will be dished out to some extent after moderate use. Doing routine flattening each time I sharpen has reduced the amount of time I need to spend on the finer stones, which saves both time and money. It also gives me the best control over the shape of the edge, which is important if I'm trying to get the very best performance out of a smoothing plane. For a plane to take a full-width shaving that is less than .001" thick, the edge of the blade must be straight within a tolerance of less than a thousandth. Until I really got serious about how I flattened my waterstones, I wasn't able to get the plane to that level of performance.

Re: same experience

Steve Knight

>very true. I tried diamond lapping plates on my makita. worked great for 20 or so plane irons (G)

Re: Japan Woodworker describes the DMTs as being..

Dave (Arlington, VA)

>John -

Thanks. I appreciate the data - and the reminder of other options. I noticed that Leonard Lee mentions using diamond stones for flattening, but after my experience with my new way-out-of-flat India Stone I thought I shouldn't just assume that a new diamond stone would be flat, too. Then when I couldn't find any references to a standard of flatness on the DMT website, I began to get uneasy. Thus the reason for the question.

Frankly, I'm not leaning toward waterstones.

Thanks again for the post.

Regards -

Dave

Re: Flattening waterstones

Dave (Arlington, VA)

>Steve -

Thanks. I am now leaning toward trying waterstones. I appreciate your tips on flattening. I had heard that you had to flatten them when they were dry. Is that your experience. Does that limit you from doing alot of blades (as I'm doing right now) because you can't keep them flat during an extended session?

Again, thanks!

Regards -

Dave

Re: Flatness of Diamond Stones

Dave (Arlington, VA)

>Fred -

Thanks for the encouragement. I guess I shouldn't be so self-conscious. I may stick a straightedge in my pocket the next time I head out to Woodcraft.

Regards -

Dave

Re: Monocrystaline Diamonds ??

Dave (Arlington, VA)

>Steve -

Thanks. I'm looking at the Nortons. I know you've flattened a few blades over the years.

As for a $400 diamond stone - I don't think so. At least, not for me.

Again, thanks.

Dave

Re: Flatness of Diamond Stones

Dave (Arlington, VA)

>Thanks for the encouragement, Pam.

Dave

Re: same experience

Dave (Arlington, VA)

>Bill -

Thanks, but I thought the cast iron plates loose their flattness, as well. But no question that the loose SiC grit would be an inexpensive way to go.

Regards -

Dave

Re: Flattening waterstones

Don Thompson, Cutler Ridge, South of Miami FL

>Why do you suppose that using sandpaper on a surface plate results in a convex waterstone?

And here I thought that method would give great results...

Re: Monocrystaline Diamonds ??

Steve Knight

>I can't even afford it (G)if you want speed get the shapton stones. far faster then any diamond stones I have tried.

Flattening waterstones while wet

Steve Elliott

>The reason to use wet/dry paper is so the stones can be flattened at any time during a sharpening session. The water also helps the paper to stick to the surface plate. Years ago I flattened my stones dry using regular silicon carbide paper, but I much prefer the wet/dry.

Great Results

Steve Elliott

>The flatness of my waterstones and the flat surface I can achieve on a blade back using them are the best I've been able to get using any method.

My comment about C weight paper producing a very slightly convex surface on the stone wasn't meant to suggest that it is a problem. I think the sponginess of the thicker paper is what makes this happen.

The standard of flatness I can reach using this method goes way beyond what is needed for most woodworking tasks. I've been working on supertuning smoothing planes more as a hobby than as a part of my actual work with wood. (I'm a professional cabinetmaker and do almost all of my work with power tools.)

One area where power tools can't match hand tools is in producing a surface that is flat and free of scratches. I'd prefer a plane to any kind of sander for flushing up a face frame or taking a snipe out of a jointed plank. Removing stock by sanding rounds over edges or leaves divots. A plane removes only the high spots and leaves a better surface.

not yet

Bill Tindall, E. TN

>As part of our tool making Odessey Phil and I flattened 3 dozen plane and chisel backs a while back (in one night). So far the cast iron for the 60 micron plate is still flat(this one gets the most use for initial flattening). It is easy to see when something isn't. when progressing to finer grits they quit cutting on the spots that are low, usually edges. I see no reason I won't get 100 flattenings out of the plate. I don't intend to ever need to flatten more things than that. some one else can inherit it and surface grind it flat again if it is ever needed.

If someone can find a cheap, widely available, source of cast iron plate this would easily be the cheapest, fastest way to abrade tool steel to create sharp edges. (we lucked out and had some surface ground plates given to us) It is so fast that I have taken to hand honeing bevels. I can keep a few careful strokes flat on the bevel, so it works for me.