Trouble with new diamond plates

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Forum topic by jklingel posted 01-10-2018 02:16 AM 1578 views 0 times favorited 10 replies Add to Favorites Watch
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112 posts in 1931 days

01-10-2018 02:16 AM

I have four fairly new diamond sharpening plates (3” x 8”) and they just tore up the sole of my planes. What is happening is (1) the ends of the plates seem high or extra rough, but not consistently. I started with a 300 grit and my 5 1/4 Stanley plane and all was well for a few seconds. Then, a nasty grind was heard and I had deep gouges in the sole of the plane. Each end of the plate did this. I tried to take out the gouges with the 600 grit plate; same thing. I put 1/4 sheets of sandpaper on the plates and fixed the sole of the 5 1/4. This was with a set of 3 cheaper plates ($110 for 3). I then tried to polish the Stanley with a 4000 grit plate from one of the big companies ($100/plate) and the same thing happened, so I fixed it with sandpaper. Next, I took my little low angle block plane and ran it on all the cheaper plates, avoiding the ends. All was well up through 1200 grit. (2) When I got to the spendy 4000 grit plate, it periodically seemed to lose a diamond or two in one spot and scratched the sole pretty badly. I fixed that with the cheaper 1200 grip plate. My questions are: Is this typical until the plates get used a bit? If not normal, how do I fix the plates? Grind the ends off a bit? (I tried that a bit; no-go.) Should I forget using the plates on planes and use sandpaper atop the plates? Then too, at what grit should one quit on the sole of a plane? 1200 seemed awfully flat and polished. Thanks for any feedback. john

10 replies so far

View GAwoodworker's profile


37 posts in 1542 days

#1 posted 01-10-2018 04:00 AM

I have run into the exact same problem with a new DMT Extra Fine that I bought. After a few uses, it seems as if diamonds came dislodged and scratched across the surface of the plate and re-embedded themselves. The result is a sharpening plate that has big scratches in the surface that gouge into what ever I am sharpening. It damages the edge of an iron when I am sharpening. I just stop at the Fine plate now and will probably get some shapton stones in the future. The other day, I used a friend’s diamond plates that he has had for 15+ years and got a massively different outcome when comparing them to mine. My new Fine plate was dramatically rougher than his Coarse plate, and he said he’s barely used it in 10+ years. We were both dumb founded. Even if he did use it a lot, massive wear on his plate still couldn’t amount to the differences we were seeing. I think the recent production in the past couple years has dramatically cheapened and quality control has gone down. I’ll be watching to see what other people say!
PS – I always flatten soles on sandpaper and a flat surface. Haven’t taken them to my plates yet. Only irons touch my pates.

View jklingel's profile


112 posts in 1931 days

#2 posted 01-10-2018 06:23 AM

GA: That is discouraging, but thanks for letting me know. I am going to contact DMT, fwiw. I don’t know who made the cheaper 3 plates; I’ll have to look in some catalogs and see from whom I bought them. Cheers. j

View Andre's profile


3567 posts in 2580 days

#3 posted 01-10-2018 06:40 AM

I would never use any type of stone on the sole of a plane, 180 -220 grit sandpaper on flat surface, I use the self adhesive stuff for auto body work, stick it on the top of the jointer.

-- Lifting one end of the plank.

View jklingel's profile


112 posts in 1931 days

#4 posted 01-10-2018 07:01 AM

from my first experience, i think i will avoid diamond plates in the future. if 220 grit is enough, then that is what i will do next time (maybe 320. super smooth looks so good….) i guess i got a bit carried away going to 4000 grit…..but, it looked so nice…. until a diamond or two got loose and scratched it! dang….

View nwbusa's profile


1022 posts in 3060 days

#5 posted 01-10-2018 10:14 AM

Have used my five DMT DiaSharp stones for several years with no problems. YMMV, I guess.

-- John, BC, Canada

View Carloz's profile


1147 posts in 1365 days

#6 posted 01-10-2018 12:19 PM

Yes, you should use diamond plates for a few hours on some cheaper tools or just a piece of steel.Out of 4 DMT plates I have one came pregrinded , probably it was the highest grit, do not remember. I used the rest to hone the iron of some cheap stanley plane and some old chisels before switching to the new planes.

View bbasiaga's profile


1243 posts in 2769 days

#7 posted 01-10-2018 02:05 PM

I am not super happy with my diamond plates. I have a DMT coarse, and fine. I did not have the same issues you are having, but after restoring a few plane blades the coarse is almost worn out. It feels very smooth now and cuts slower than it did when I got it. I tried cleaning it etc but no help. I probably should have used sandpaper for those tasks in hindsight, but still I feel it should last longer. The fine stone is still good. No real issues with it I guess, other than it is probably a little more coarse than you really need for a first Sharpening step.

I will probably go to splash and go water stones at some point.


-- Part of engineering is to know when to put your calculator down and pick up your tools.

View JayT's profile


6402 posts in 2985 days

#8 posted 01-10-2018 05:09 PM

Diamond plates do have a break-in period where they cut more aggressively than the grit until some of the diamonds fracture and settle in. I’ve been using EZE-Lap plates for several years now and am very happy with them. Took sharpening half a dozen plane irons or so before they broke in and then have performed admirably since.

When doing plane restorations, however, I use sandpaper rolls on granite. More for the length than to save the sharpening plates. I usually stop at 220 for users. Any more than that is just extra effort for no performance gain. If you want to use higher grits to get a mirror finish because that’s the look you want, have at it, just don’t expect the plane to work any better.

-- - In theory, there is no difference between theory and practice. In practice, there is.

View jklingel's profile


112 posts in 1931 days

#9 posted 01-10-2018 05:51 PM

ok, thanks all for sharing your experiences. j

View jklingel's profile


112 posts in 1931 days

#10 posted 01-12-2018 05:29 AM

just a fwiw. i took the diamond plates out today and ran the backside of some of the plates over the ends (diamond side up) of each plate. i found that the problem areas were really very small, and primarily right in the corners. as i ground the backside of a plate against the diamonds of another plate, i could see wear on the diamond face in areas that were mostly about 1/16” long and maybe 1/32” wide. one bad spot was about 1/32×1/32; a very nasty corner. possibly, areas the manufacturer never intended or expected anyone to use. i got very little gouging anywhere else, until i lifted the being-beat-up plate to “bevel” the diamond face, as i wanted to make sure the bad spots were removed completely. i did not run a plane over any plates to check. i think i learned my lesson on that deal. anyway, the plates appear to be very usable for what i gather is their intended purpose; sharpening chisels and blades…. and very large fishing hooks. seriously; if you don’t have a file/stone/diamond file in your tackle box, you better get one. those hooks need to dig into your fingernail nicely to be usable. but, i digress…..

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