Sharpening Plates not flat?
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7 July 2018 at 1:51 pm #549180
Hy
I’m still having problems with my sharpening plates. First they didn’t get my plane soles flat, so I’ve switched to sandpape on a flat surface.
Now I’m trying to initalize my chisels. I initalized the flat face of my chisels on the coarse plate. As a result I see that the plate hits the chisel on the whole face. Then I go to the medium (600) plate with the handle pointing to me, exactly as shown on the DVDs and youtube videos. On the medium stone the chisel face hits only the middle part. That would mean that the stones are NOT flat, or am I getting something wrong. The sharpening process is getting very frustrating. I’m sharpening for the last 4 weekends and I still don’t get results.
Any help would be very much apreciated.Attachments:
You must be logged in to view attached files.7 July 2018 at 4:12 pm #549185What type of chisels are those and what type of stones do you have? They don’t look like diamond plates. You might try going back to your flat plate and some medium grit wet/dry sandpaper (250 – 400 grit) and see what happens. That will let you know if it’s the stone or not. Be sure you’re using something flat like 10mm or thicker glass – not just a piece of MDF. It looks like the back of that chisel may be crowned instead of hollow and if that’s the case, I would consider the chisel defective. You can flatten one that’s crowned, but it takes a lot more work.
7 July 2018 at 4:31 pm #549187You’re not saying only put an inch of the back of the chisel on the stone are you? Apart from being hard to maintain registration, you definitely don’t want to grind a step-down in the back of the chisel.
I would personally use microlapping film on some float glass for this, start at 100 micron and go through the grits all the way to 1 micron then carefully strop it and you’ll have a flawless flat chisel it will likely never need work again once it’s been initialised, I like you was really struggling with diamond stones, the problem is not the stones, they just don’t take enough steel off, I use them as my main sharpening plates, but for initialising I prefer the special microlapping film.
7 July 2018 at 5:42 pm #549190Ther are EZ-Labs Diamond stones (like Paul Sellers suggests). These are Aldi chisels ( as Paul Sellers suggests)- I’ve also flattened one chisel on a thick and flat stone plate with 80 grid paper. Then I went on the coarse grid plate and I can see that it hits the whole face of the chisel. Perfect so fa. But then as I rotate the chisel 90 degrees (because the medium plate is in the middle of the holder) it does’nt hit the full face of the chisel. For my understanding this should proof the diamond plates are NOT flat. My big problem is that Mr Sellers says again and again that every single diamond plate he used has been perfectly flat. I’m a beginner and maybe I’m getting something wrong.
Next step will be to try going through all levels of sandpaper on the flat stone. If this works I guess there is something wrong with the diamond plates.7 July 2018 at 6:57 pm #549193Your stones should be okay. Eze-lap stones are normally very good. If you can move your medium grit stone to the outside temporarily, I would try that. I have never had a chisel myself out of the box that had a perfectly flat back. All the ones I ever bought had a slight hollow in the middle which I don’t worry about. Perfectly flat would be fine too, but if the back is convex, it takes a lot of grinding to remove that. You have to keep going until you see a uniform scratch pattern completely across the tip for maybe 15mm or so and usually down the sides and toward the back near the bolster, but the tip is what’s important. Try the sandpaper as you indicated just to make sure it isn’t the chisel. That center stone works great for sharpening but it’s hard to deal with for flattening. I usually just move mine over if I’m flattening something.
[quote quote=549187]You’re not saying only put an inch of the back of the chisel on the stone are you? Apart from being hard to maintain registration, you definitely don’t want to grind a step-down in the back of the chisel.[/quote]
Well, I was more suggesting that I don’t believe it is necessary to attempt to flatten the entire back of the chisel. That’s a lot of steel and most of it will not likely contact the wood, save for paring cuts. Maybe I’m crazy.
7 July 2018 at 7:12 pm #549195I totally agree with you on that. Those hollow spots in the back that are away from the cutting edge don’t hurt a thing. It’s only out at the cutting edge that it has to be flat. I guess some guys want the entire thing to look like a mirror and it you want to spend the time, it won’t hurt anything, but it doesn’t help the way the chisel or plane functions either. My point is that when you go to pare with the chisel, you wouldn’t want an abrupt step in the back. So to avoid that, I start flattening with as much of the back as possible in contact with the stone (as if I wanted the entire back surface flat), but as soon as I get ~15mm of flatness across the entire cutting edge, I quit. No point in doing any more. I think you and I are on the same page.
7 July 2018 at 7:16 pm #549196CHeck the plates with a straight edge. See if the ruler or whatever rocks from end to end or diagnally across the face. You can also see if it is dished as the edge will not touch the stone in the center.
I’ve experienced this with diamond plates too. I have no proof of this, but my interpretation is that the plates are rigid and there’s no such thing as perfectly flat. There’s always some tolerance. So, when you move from one plate to the next, there will be a slight difference in registration that the new grit must grind off because the two plates differ in flatness at the level of the manufacturing tolerances. My belief is that diamond plates just don’t have much abrasive on them. They are fine for working a bevel, but for hogging material off of the back of a blade, they are slow. So, my theory is that you move to the new plate, the registration is just a little different, but because you have so much area to grind, it takes forever to adjust to the new plate’s notion of flat. By contrast, there is so, so much more abrasive on a piece of abrasive paper that you never even notice the change over. You rapidly adjust the back of the blade and remove the prior scratches.
That’s my theory. I’ve experienced what you are experiencing many times, albeit with the same plates (a mixture of DMT and EZ lap). At this point, I’ll try to flatten a tool on the diamond plates, but if I don’t get what I want within a few minutes (rarely do), I switch to paper bonded to a granite block or to my old water stones.
On the other hand, there isn’t much material on a bevel, so the diamond plates are good for them, although there’s no doubt that you can experience how slow diamond plates are if you need to drop the heel of a plane iron from a fat 35 down to 25 degrees.
Just a hypothesis on my part.
8 July 2018 at 5:10 pm #549216I know that only the fisrt 10 mm have to be flat, but this doesn’t solve the problem of plates that are not flat. When I got the plates I’ve checked them with a Starrett combination square and the have been flat.
Maybe I’m just the unlucky one who got plates that are not flat. We’ll see. -
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