One of my plane blades no longer get sharp
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- This topic has 3 replies, 2 voices, and was last updated 5 years, 3 months ago by Ghal.
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Howdy. I’ve run into what I suspect is a newbie sharpening problem, but it’s stumped me for a few weeks running now and I’m not sure what to do.
The problem is my Lie-Nielsen #62 low angle jack plane blade won’t get sharp any longer. At least, not sharp enough to plane anything. I can’t get it to develop a wire edge, at all. Instead, the back of the blade edge develops a…little hump of sorts? But never a wire edge.
As quick background, my sharpening setup is currently a 1,000 / 8,000 Ohishi combination water stone, which I flatten with the Dia-Flat lapping plate. That stone was a recent upgrade from a no-name $25 stone from Amazon I got a few years ago when I first began dabbling in hand tools. This year I gravitated to them more fully, and since the old one from Amazon was getting crumbly as I worked through it, I picked up the better stone. I use a honing guide (mostly due to a wrist injury that causes issues when I try to freehand sharpen).
I have a low angle block plane that sharpens up nicely, along with my chisels. The scrub and router plane blades also get very sharp. They all develop the telltale wire edge and polish out nicely. The jack plane blade never develops a wire edge any longer. At all.
I’ve re-ground the blade back to 25 degrees using sandpaper and the back of the Die-Flat plate, and resharpened. I’ve polished the back and confirmed it’s flat. I’ve done the ruler trick. I’ve sharpened again for so long the secondary bevel went from tiny to half the width of the bevel. When I touch the blade to my fingernail, it catches and shaves some nail off, which I’ve heard is a good test for sharpness.
But when I set the plane up, it just taps against the edge of a board – any board, pine, sapele, anything – and then skims over the top creating a little dust. I can force it down very hard with the blade extended a long ways and get some short, deep divots, but that’s it. It’s done this for a long while, even when I made my Sellers’ work bench (installed the vise last weekend) – the top was flattened as much with my scrub and block planes as the jack (it was not fun). I’ve had the plane since March and it worked flawlessly for the first six months or so. Now, I’m at my wits end.
Does anyone have any ideas? Any help or suggestions at all would be greatly appreciated.
9 December 2018 at 6:42 am #553800Pictures?
Especially on the flat side. You may have overdone the ruler trick and thereby lost the blade clearance with the low angle bevel up iron. Charlesworth shows only 1 mm bevel from the ruler trick.
Properly done, the ruler trick is only a few strokes. David Charlesworth says 20-30 short strokes on an 8K-10k Waterstone only on the first 1/4” of the stone.
The stone and the iron must be perfectly flat for it to work. (your Lie Nielsen iron was lapped flat at the factory. It’s not likely you made it better)
And he shows the secondary bevel being made with THREE Pull stokes on the same fine stone after you have removed the previous secondary bevel with a coarser stone. You will probably need to start over with the primary bevel.
Hope that helps. Watch his video for refresher.
And keep sight of the goal. On some irons he wire is small. I often can’t find it. What counts is the edge, not the wire.
- This reply was modified 5 years, 3 months ago by Larry Geib.
Thanks for the tips. That’s the video I watched when I learned about the ruler trick; I only did ~20 or so strokes on the 8,000 side of the stone. There’s a razor-thin polish line on the back. I polished with the back flat to the stone a bit on the 8,000 side, just enough to confirm it was flat, so I don’t think I threw anything out. But to be clear, I only tried these after weeks of a non-functional plane.
I’ll take some pictures to post tomorrow – going to re-grind the now-massive secondary bevel back to 25 degrees and start over.
Well, I figured it out, I apparently just needed to write out the situation to get my gears turning. The key bit was how the blade would tag the edge of a piece and then run over the surface of the material, not cutting. I remembered something Paul said in one of the Q&A Youtube videos (I think) about a mistake novice freehand sharpeners often make: they will put a round on the bottom of the blade, so that the round contacts the material before the cutting edge. My blade was exhibiting the same behavior. After 3 hours of re-grinding with sandpaper this morning (as measured by two and a half Fine Woodworking podcasts), I ended with a nice burr on the back, finally. I stepped back through the grits, and four strokes with the 8,000 stone put a burr on the back, in the end. It cuts like it should now. (Which meant I could spend seven hours in the shop working on Christmas presents, just in time.)
I use a honing guide, so I’m trying to think of how I messed up the blade so badly. The plane went south while I was milling up the reclaimed material I used on the workbench. Much of it is very old, hard pine from homes built ~60 years ago and it was tough on the plane. My hypothesis is, at some point it got dull and stopped cutting, and started running over the surface of that very hard, undulating pine. I think I basically rubbed a rounded edge into the bottom of the blade somehow.
Lesson learned – I needed to sharpen up much more often (I remember powering through when I knew I should sharpen, because of how often I was doing it while working that old pine).
Not my finest moment to announce myself into the forum with a decidedly rookie mistake (then again, I am a rookie), but I thought I’d explain how I fixed it in case anyone else does this.
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