Strange Lapping Results

[Nikolaj33]

Hi, I was flattening the back of an old 1″ Marples chisel. I first did it on 80 grit sand paper on thick glass. After about an hour it was done. Then onto 120 sand paper. But when I moved to EZE lap 240 stone, it seemed like it was abraiding the belly only, as if though I haven’t already flattened it. I decided to get back to using sand paper on glass. I had some wet and dry 360 and 600 at hand and the results were great, it just polished the already flattened chisel. But now I tried using the 1200 EZE lap and the same thing happened. It was abraiding the belly only.

I checked the stones then and none of them were actually flat. I checked with 0.003 filler gauge, I didn’t bother further. I checked the glass just in case and it was flat. What should I do? I thought EZE laps should do the job. By the way, I only had them for a few months and I haven’t used them heavily.

 

[Trevanion]

You spent HOW LONG flattening the back? :shock: Are you 100% sure you didn't curve the back at all? I wouldn't have started with 80, possibly a little too coarse and very easy to get carried away.

I would call 0.003 extraordinarily flat for a diamond plate.

 

[Ttrees]

On course abrasive like that try pulling the chisel only to register off of the long axis, and not create those problems
of dubbing around the edges more and more with every pass, and ending up with a belly across the width.

 

[Nikolaj33]

The chisel appeared to have a twist to start with. That's why it took that long.

 

[Osvaldd]

Straightness, flatness, grit fineness, precise bevel angles - not saying its not important but it's not that important.

 

[Ttrees]

Straightness, flatness, grit fineness, precise bevel angles - not saying its not important but it's not that important.

To quote Mr Cosman
An edge is only as good as the lesser of the two surfaces.

 

[Trevanion]

To quote Mr Cosman

While he's trying to sell you a £300 30,000G water stone :lol:

 

[Ttrees]

Concerning Mr Cosman
I would have expected a reply on the new chisels advertised with removable handles to be of topic
because it enables you to lap a chisel back easier.
A nice diamond hone is pretty good to have though, no need to buy such an expensive one
I use a 40 quid one from Dia-sharp.

 

[Orraloon]

Like others have said 80g is a bit harsh unless you have a real lot of metal to remove. If the paper is not sticking down to the flat surface then you are creating a belly or bulge. A big belly on an old chisel may not even be worth the work.A hollow back helps things as you only really need a small flat polished surface near the cutting edge. Japanese chisels are a prime example of this. Have a watch how Mr Sellers prepares the back of a chisel. Explains things fairly well.
Regards
John
https://www.youtube.com/watch?v=Ki8tt-VjwqI

 

[custard]

The OP did absolutely the right thing in starting with 80 grit.

Hobbyists often seem in a race to get to finer grits, where as professionals know that the lion's share of sanding is done with the coarser grit. You basically get the job done with 80 grit, so that's where you put your time and effort, after 80 grit you're just using finer grits to progressively erase scratch patterns, you're not actually flattening or shaping.

Do you need dead flat backs to your chisels? If you do really fine work then you need really fine tools. Note I didn't say skilful work. There's plenty of incredibly skilful work, such as traditional boat building for example, that doesn't require such finely fettled tools. But if your objective is exquisitely crafted furniture, then you'll need at least some of your chisels with dead flat backs.

 

[D_W]

Straightness, flatness, grit fineness, precise bevel angles - not saying its not important but it's not that important.

To quote Mr Cosman
An edge is only as good as the lesser of the two surfaces.

This is catchy sounding, but not true. There's no reason not to polish both sides of a bevel, but an edge sharpened to 1000 grit on one side and 1 micron on the other is far finer than one sharpened to 1000 grit on both sides.

Try it.

If you're in the flatness obsession crowd, it doesn't hurt to chase the spider webs off of the back of your tool and refresh the flat surface with a little bit of bite once in a while. But the webs only matter if they show up on the wood and you're actually finishing off of the plane.

Rob is good at what he does, and he's a genuinely nice fellow, but he's aiming at an audience that you don't want to be in too long if you're going to get something done.

 

[Ttrees]

but an edge sharpened to 1000 grit on one side and 1 micron on the other is far finer than one sharpened to 1000 grit on both sides.

How does an edge with 1000 grit on one side, and 1 micron on the other, compare in durability,
with an edge that's 1 micron on each side?

BTW, there's a washita thread on the general woodworking

 

[basssound]

To quote Mr Cosman

While he's trying to sell you a £300 30,000G water stone :lol:

And £120 winding sticks....

 

[Ttrees]

More of an incentive to make your own, I suppose.

 

[thetyreman]

I would make my own but I'm just too torrified so sadly I'll just have to use my aluminium ones by veritas!

 

[Racers]

How did you fix your 80 grit down?

I once lapped a chunk of steel on course paper that was not fixed down, when you push it forms ripples that abrade the front and back more than the middle.
You need it fixed down or stretched tight to avoid the problem.

Pete

 

[D_W]

but an edge sharpened to 1000 grit on one side and 1 micron on the other is far finer than one sharpened to 1000 grit on both sides.

How does an edge with 1000 grit on one side, and 1 micron on the other, compare in durability,
with an edge that's 1 micron on each side?

BTW, there's a washita thread on the general woodworking

For edge life, it depends on what you're doing. If you're taking .001 shavings, I'd imagine that the edge polished on both sides would hold up a little better. For work any less fine, the two would be similar. For mid and thick shavings, clearance and lack of edge damage becomes the limiting factor - mostly clearance.

From the standpoint of "what's the advantage of doing only one side?", there really isn't much, except for one thing - polishing one side of an edge with a super fine stone makes for a very weak or nonexistent wire edge whereas two 1k stone finishes (bevel and back) can make for a tenacious wire edge if you don't burnish the wire edge off with compound.

When I first got a metallurgical microscope, I set out to sharpen 5 ashley iles chisels from 1200g diamond to 0.5 micron pigment (not honing compound, just the pigment that is only chrome ox). I thought I would be able to punish the wire edge off of the 1200g edge reasonably easily, but I couldn't do it with leather. On everything else, the wire edge came off very easily.

I know there are proponents of using compounded leather to do that, but you're just moving yourself further along the wear profile by making that big of a step.

Not climbing a hill with one arm here on anyone, just pointing out that Cosman's statements (and anyone who teaches beginners) tend to be catchy but they don't reflect what's done by professionals.

The finest craftsman I've ever known does apply compound to his edges, though, and he seems to really like spyderco stones (George Wilson). I don't particularly care for spydercos, but my best work isn't close to George's worst. Not remotely.

I've got all kinds of ideas about edges and what's ideal, along with steels and why they're used in tools now (generally maker ease), but I don't think most people like them!!

 

[D_W]

One side comment - a lot of teachers talk about methods. One thing that I think folks didn't like that much about George (he was harassed by beginners on SMC as being arrogant - he's definitely not lacking in confidence, mostly because he was stiff enough with know nothings to tell people that they were saying something that was just incorrect/wrong and you couldn't try to gussy it up with "YMMV" and say that it was just opinion)....anyway, what I like about him is that he talks a lot about results, and not that much about method. In general - for everything.

The only reason anyone has a clue what sharpening stones he uses is because people harped on him endlessly "that's really nice work. What kind of sharpening stones do you use?". I talk to him from time to time, and he was always saying "OH GOD....could we stop talking about sharpening stones!!".

Funny that he would say that to me (he knows I like stones). I didn't bore him with talk about stones.