Thread: Grinding plane irons

Andy, prepare to be bamboozled.

For me, I only grind when I get a new "old" plane blade to establish the bevel and frequently to remove chips, skews and associated deprivations.

I ensure the back of the blade is flat and try my best to polish out and milling marks in the first 5 mm of the blade to ensure a smooth, sharp edge.

I am lucky as my set up is 46 & 80 grit 50mm wheels on a dry grinder then the Torment at 220 and 1k. Then off to the water stones at 1k and 4k.

Unless the blade is especially damaged or no bevel has been established, it's a quick go on the 80, then on the Torment @220 & 1k, then the stones, then into the plane for "testing" or is it "playing" as my wife believes.

I'd love to help, but I don't grind plane irons often enough to have more than a nodding acquaintance with it.

Never had a problem keeping them in shape with a couple stones. Rarely had any chips or chunks, and when they were present they were small. Never let the iron get dull enough to need more than a few quick swipes.

Maybe I'm OCD over plane irons and keeping them always sharp, but I've managed to dodge any heavy work on them as well. Maybe there's a message in that all by itself?

reply in the quote

Originally Posted by groeneaj

Questions:

1. When grinding a plane iron, when do you know when to stop?
If refreshing a blade once the secondary bevel gets too big for efficient honing, grind out most of the secondary bevel, no need to grind it all out this offers some protection to the edge of heat sensitive steels (not HSS) and saves time and blade. If you must grind out the bevel, eg a chip, once the sparks come over the back of the blade you know you're grinding the edge, take care on heat sensitive metals (not HSS) and grind until the chip is gone.
2. Once you have stopped, do you leave the hollow grind?
Yes, it offers more efficient honing.
-if you do leave the hollow grind, do you go straight to sharpening on the 1000, all the way up to 8000 as per normal?
Yes
-if you don't leave the hollow grind, what do you do?

3. What are the difference betweens grinding bevel up/down irons
You may need to put a camber on BU irons depending on application, eg smoother.

Input would be much appreciated,

Andy

Thanks for the replies

Another question if you don't mind, a BU plane that has a 25 degree iron plus the 12 degree bed angle results in a 37 degree cutting angle, which is true, but does this mean they havnt honed a secondary bevel? Does it mean they have just honed it at 25 degrees? If so, I thought this would not be as efficient as if they honed at 3 or 4 degree secondary, which would mean a 41 to 42 degree cutting angle.

Andy

Originally Posted by groeneaj

Thanks for the replies

Another question if you don't mind, a BU plane that has a 25 degree iron plus the 12 degree bed angle results in a 37 degree cutting angle, which is true, but does this mean they havnt honed a secondary bevel? Does it mean they have just honed it at 25 degrees? If so, I thought this would not be as efficient as if they honed at 3 or 4 degree secondary, which would mean a 41 to 42 degree cutting angle.

Andy

I suppose if they say they have a 25º iron, they mean 25º in a honed condition. That means they have possibly honed a wide bevel at 25º or hollow ground at 25º and honed at 25º. A BU plane set this way would be good for end grain, I use my block plane this way. You'd use a higher secondary bevel for crankier grain, probably fine tuned for the wood you're currently working on.

what mic-d asid is

I'm happy to explain in more detail if you need, but mic-d has given the 'solution'... so if you are happy then anything else is 'detail and tricks'.

1) Some people qualify 'grinding' as re-establishing a new primary bevel, which could be done on a number of media. In answer to you question; when I grind on a dry wheel I usually stop when the new bevel is within 1mm of the edge. This way you're not wasting any steel and lessening the risk of de-tempering the edge. With harder steel or steels that will clog your wheel be sure to true the wheel regularly with a diamond jig or 'T'.

2) Most definitely. On most thin bevel down irons I grind at ~27 degrees and leave the hollow alone. Then I'll move to stones for a 30 degree secondary bevel for honing and polishing.

3) The only BU planes I own are block planes so I'm no expert, however, in my experience there is no difference. That said because the blades are so narrow I've never had the need to take one to a grinder. Grinding on a coarse stone has been sufficient. I still apply a secondary bevel to these, though I believe some will polish the entire bevel on larger BU planes.