Help examining dmt stone

[Adam Grund]

I’m working on flattening my chisel backs, and I have a 4 stone kit from dmt (x coarse, coarse, fine, x fine)
Starting low and working my way high, I’ve worked 3 chisels now, and on my 3rd one I’ve noticed the x fine has some lines in the stone. I cleaned the stone with bar keepers friend and a toothbrush, didn’t seem to make a difference. When the chisel runs over these spots, it has an increased resistance, almost like it’s sticky (in the full motion it feels like the chisel is hitting speed bumps and is actually quite annoying)
The spots are small enough that when I run my finger across the stone they don’t really feel any different, but looking at them they look pretty shiny, almost like there is no diamonds there.
I’m just trying to figure out if it is normal, a defect, or something I did.


Thanks,
Adam
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[Frederick Skelly]

Adam, I'm not sure the answer to your question. But if you don't get one here, call DMT. I had a problem with one of mine 4-5 years back and they took really good care of me.

Best of luck,
Fred

[Thomas Wilson]

I have the same DMT set. Mine have been used to flatten backs of a number of chisels and plane blades. It has been hard wear. Mine have not worn like yours. I can feel more resistance (bite?) at the ends of the stone where less wear is typical. The middle is has gradually greater wear toward the center. Yours looks more like a manufacturing defect than normal wear to me. Perhaps, the coating that holds the diamond grit is not uniform or the plate is not flat. How is sharpening affected?

[Adam Grund]

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I have the same DMT set. Mine have been used to flatten backs of a number of chisels and plane blades. It has been hard wear. Mine have not worn like yours. I can feel more resistance (bite?) at the ends of the stone where less wear is typical. The middle is has gradually greater wear toward the center. Yours looks more like a manufacturing defect than normal wear to me. Perhaps, the coating that holds the diamond grit is not uniform or the plate is not flat. How is sharpening affected?

The fine stone had the same sort of marks, but unlike the x fine, I can still see grit in the marks. The x fine appears to be super smooth, almost like it’s missing the diamonds and down to the plate (I don’t know if that’s really the case, but that’s what it appears like)
The coarse and x coarse are discolored (normal from what I read) with no marks.
As best as I can tell, sharpening is unaffected (I think? I‘m no expert here, this is my first go at sharpening ever) , as I move up and down the whole stone and the scratches are pretty uniform across the chisel back. It’s just that resistance (or lack of) as I pass over those spots and then hit the grit again.
I used a straight edge across several points of the stone and no light passed through, so I think it’s pretty flat.

[William Fretwell]

If there are no diamonds in the patches the vacuum effect of two wet flat surfaces pushed together would explain the stiction.
Just get it replaced.

I hope the picture above is the result from the coarse and not the fine stone!

The polished back right at the blade edge meeting the polished bevel creates sharp. Yes that sounds obvious but not easily achieved. It is right at the edge that counts, think 1/20 mm. Highly visible scratches like that at the blade edge would seriously degrade the edge and encourage chipping. One reason stropping may work so well is the force is not spread out but directed right at the edge where it counts.

I spent quite some time sharpening plane blades yesterday, throwing away metal to remove small edge chips then polishing with a fine stone. The burr on the blade back created by the fine stone is VERY small under microscopic examination. It was very gratifying that my fingers could easily detect such a small burr. The burr was at 90 degrees to the back and very consistent along the edge, also gratifying. The fine stone rapidly removed the burr, followed by 8 strops on leather and green compound (Lee Valley). The microscope then shows a scratch free union of two planes with a straight edge. My system is water stones, I have used diamond plates in the past.

The whole sharpening thing is a never ending topic here. Easy to get sharp enough to start working wood but seeking perfection grows on you. It does make life easier, the finish IS better. A well tuned plane will put the best finish attainable on a wood surface.

[Reed Gray]

I have a set of 4 of the stones, maybe 30 years old. There is a huge difference in their 'lapping' plates and the stones which have the holes in them. Mostly it is flatness, with the lapping plates being a lot flatter. Not sure if that is the problem or not. I did get one of the Trend 300/1000 grit stones. The 300 grit side was slightly concave, the 1000 grit side was pretty much dead flat. Run a chisel sideways on the 300 grit side, and I got scratch marks on the edges, but not in the middle of the chisel back. Not quite so bad with the old DMT stones.

robo hippy

[Adam Grund]

If there are no diamonds in the patches the vacuum effect of two wet flat surfaces pushed together would explain the stiction.
Just get it replaced.

I hope the picture above is the result from the coarse and not the fine stone!

The polished back right at the blade edge meeting the polished bevel creates sharp. Yes that sounds obvious but not easily achieved. It is right at the edge that counts, think 1/20 mm. Highly visible scratches like that at the blade edge would seriously degrade the edge and encourage chipping. One reason stropping may work so well is the force is not spread out but directed right at the edge where it counts.

I spent quite some time sharpening plane blades yesterday, throwing away metal to remove small edge chips then polishing with a fine stone. The burr on the blade back created by the fine stone is VERY small under microscopic examination. It was very gratifying that my fingers could easily detect such a small burr. The burr was at 90 degrees to the back and very consistent along the edge, also gratifying. The fine stone rapidly removed the burr, followed by 8 strops on leather and green compound (Lee Valley). The microscope then shows a scratch free union of two planes with a straight edge. My system is water stones, I have used diamond plates in the past.

The whole sharpening thing is a never ending topic here. Easy to get sharp enough to start working wood but seeking perfection grows on you. It does make life easier, the finish IS better. A well tuned plane will put the best finish attainable on a wood surface.

I have shapton water stones to use as my primary sharpening system (though the coarsest I bought was 1k)
When I finally decided to get started preparing the chisels, I started reading the coarse Shaptons weren’t great for flattening because they dish really fast.
So I got about $50 in wet/ dry sandpaper, contact cement and got a hunk of granite from a local granite place, went to town.
I’m not sure if it was the brand (3m) or that I was using water with it, but I was flying through sandpaper, and peeling it up and scraping the glue got real old real fast.
This led me to the diamond stones, and I really only intended to get the x coarse, coarse, and fine- but for another $10 I could get the 4pc kit that included x fine.
I might just use the 3 stones and jump to shapton 1k and up from there.
I don’t have a big area to work with right now, so I haven’t drug out the waters. My thought was to get all the coarse work done on all the chisels so I can get those stones out of the way and then move on to the water stones
I’m not trying to spend all my extra money on sharpening supplies, but it seems that way in the last month or so

[Russell Nugent]

For gluing sandpaper to glass I use Elmer's spray adhesive, a light spay on the back of the sheet, let it dry for a minute, stick it down, use it, peel it up, wipe with mineral spirits and repeat.

[Tony Shea]

I honestly think using sandpaper on float glass/granite surface plate still might be the best way to flatten backs. I have tried just about every method there is, diamond stone, kannaban plate with loose silicone carbide, kannaban with loose diamonds, sandpaper, etc. Flattening blade backs is hard work and the pressure you apply is not what diamond stones are designed for. This heavy pressure and intense back and forth motion quickly pulls the diamonds off the surface of the plate. I will say that loose diamonds on a flat steel plate works well but eventually dishes the steel plate over time. Eventually after all this experimentation I've gone back to sandpaper stuck to plate glass. The longer the plate glass the better as you are changing sandpaper much less often. I also like having a piece of wood help put pressure down instead of just my hands as it helps apply pressure evenly and doesn't cramp my hands. I typically start with 120 grit and see how quickly that works and if absolutely necessary move to 80 if there's too much for the 120. My goal in flattening blade backs is efficiency, I hate this process and want it to be done as fast as possible. Therefore I believe the fastest and cheapest method is sandpaper on plate glass.

I'm not sure where he's at these days but David Weaver used to be a great resource on this very subject. He has a YouTube channel now and believe there might be some videos of this process on there as well as some old threads here at Sawmill. Unfortunately he left Sawmill due to some personal reasons and has been missed ever since. Everything I know about flattening blades is certainly a spin off or exact copy of his guidance. He also has some great information on plane making, sharpening, planing, etc....

[Robert Hazelwood]

I honestly think using sandpaper on float glass/granite surface plate still might be the best way to flatten backs. I have tried just about every method there is, diamond stone, kannaban plate with loose silicone carbide, kannaban with loose diamonds, sandpaper, etc. Flattening blade backs is hard work and the pressure you apply is not what diamond stones are designed for. This heavy pressure and intense back and forth motion quickly pulls the diamonds off the surface of the plate. I will say that loose diamonds on a flat steel plate works well but eventually dishes the steel plate over time. Eventually after all this experimentation I've gone back to sandpaper stuck to plate glass. The longer the plate glass the better as you are changing sandpaper much less often. I also like having a piece of wood help put pressure down instead of just my hands as it helps apply pressure evenly and doesn't cramp my hands. I typically start with 120 grit and see how quickly that works and if absolutely necessary move to 80 if there's too much for the 120. My goal in flattening blade backs is efficiency, I hate this process and want it to be done as fast as possible. Therefore I believe the fastest and cheapest method is sandpaper on plate glass.

I'm not sure where he's at these days but David Weaver used to be a great resource on this very subject. He has a YouTube channel now and believe there might be some videos of this process on there as well as some old threads here at Sawmill. Unfortunately he left Sawmill due to some personal reasons and has been missed ever since. Everything I know about flattening blades is certainly a spin off or exact copy of his guidance. He also has some great information on plane making, sharpening, planing, etc....

Agree 100%. Coarse sandpaper stuck down well to a hard flat backer just beats anything for flattening tool backs and plane soles. Just keep the paper fresh- it cuts more in the first two minutes of use than in the next 20, it seems. But even with all the changing of paper and cleaning adhesive, for these jobs it's still better than any diamond stone I've used. Maybe 10 years ago I bought a foot-long "x-coarse" DMT for these jobs. If I remember right, it was pretty aggressive at first but not amazingly fast, and it did seem to get slower after some use. I think the high pressures used in back flattening are not so great for these stones. It's still useful for conditioning other sharpening stones, and for odd jobs on carbide or HSS.

[Tony Shea]

Agree 100%. Coarse sandpaper stuck down well to a hard flat backer just beats anything for flattening tool backs and plane soles. Just keep the paper fresh- it cuts more in the first two minutes of use than in the next 20, it seems. But even with all the changing of paper and cleaning adhesive, for these jobs it's still better than any diamond stone I've used. Maybe 10 years ago I bought a foot-long "x-coarse" DMT for these jobs. If I remember right, it was pretty aggressive at first but not amazingly fast, and it did seem to get slower after some use. I think the high pressures used in back flattening are not so great for these stones. It's still useful for conditioning other sharpening stones, and for odd jobs on carbide or HSS.

There's no doubt that large diamond stones have their uses in the sharpening station, I just don't think initial flattening is that use. I'll use them to refresh a blade back after years of wear on the blade. After using blades for years, chisels and plane blades, they inevitably get slightly out of flat and scratched up. If my 1000 grit stone wont quickly get that blade back to flat I'll jump to my diamond stones, typically I won't let it get to that point though. All the tutorials and videos about back flattening claim you only have to do this once for the life of the blade. I personally don't think that's 100% true and the blade back should be maintained from time to time. Of course that depends on usage.

Sorry about going slightly off topic on the OP. I just think your diamond stones should be reserved for actual sharpening or flattening of stones and not the brutal process of initial blade flattening. The diamond stone binders just aren't designed for that process. And Robert makes a great point about changing/cleaning your paper often. Luckily I haven't had to do this process for quite some time as most of the higher end blades/chisels come to you very flat from the manufacturer.

[Adam Grund]

Sorry about going slightly off topic on the OP. I just think your diamond stones should be reserved for actual sharpening or flattening of stones and not the brutal process of initial blade flattening. The diamond stone binders just aren't designed for that process. And Robert makes a great point about changing/cleaning your paper often. Luckily I haven't had to do this process for quite some time as most of the higher end blades/chisels come to you very flat from the manufacturer.

I don’t mind at all, I’m here to learn.
I looked at Derek’s website and read his process, that’s how I got started in the sandpaper- I think maybe I’ll look for some low tack glue and see if that eases the frustrations when I have to change the paper.
All the chisels I’ve started out on fine (600 grit) but had to drop down to x course (220) but even at 220, I think maybe between 5-10 min for an even scratch pattern.
The chisels are Narex Richter, so not super budget but not high end premium either.

I do appreciate all the help!