Tips on lapping plane blade back?

[Evan Van Dyke]

Working on restoring/rehabbing some Stanley/Bailey planes. My #5 is done & working very well - I can get smoothing-plane thin shavings from it, though it is not destined to be a smoother.

I am having trouble with my #4. After a lot of trouble getting the cap iron to mate well with the blade, I have ID'd the problem as a very not-flat back of the blade. Now, I could drop $50 on a new blade from Veritas or wherever, but I'd like to be able to true this one up. About 2 hours on the X-Coarse diamond plate yesterday improved it from a full 1/4" across the whole edge that wasn't flat to a single stubborn corner. Other than just keeping on grinding at it - anything else I could try to fix this? I have enough amazon points to get a "free" XX-Coarse diamond plate, and maybe I'll just do that to speed things up. It can sit on the shelf most of the time until I need it I guess.

456161

[Jerome Andrieux]

Low corners are annoying.
I would just camber this blade, use the 5 blade in the 4 and call it a day.

[Mark Gibney]

At a Lie Nielsen event a rep demonstrated flattening the backs of old plane irons by cyclying through three grits of sandpaper over and over - coarse, less coarse and medium. He claimed it's much faster than staying with a single grit until flat.

I have not tried this so I can't speak to it personally, but I wish I had known about the method many years / plane blades ago.

[Derek Cohen]

I use 120 grit on a 1m long granite plate. This makes for fast flattening.

Website article here: http://www.inthewoodshop.com/WoodworkTechniques/Lapping%20the%20Backs%20of%20Blades.html

Regards from Perth

Derek

[Evan Van Dyke]

Low corners are annoying.
I would just camber this blade, use the 5 blade in the 4 and call it a day.

That is both a smart idea, and depressing. I have 2 #5s, and 1 #4 - I can only turn one of them into a scrub. I (thought) I had already planned the worst iron of the 3 for the scrub plane, but I suppose I could check again on the one I haven't touched yet how bad it is and play swapsies. It isn't a franken-plane if I just swap the blade, right? (I also have a #7, but that's a wider blade so N/A for this)


At a Lie Nielsen event a rep demonstrated flattening the backs of old plane irons by cyclying through three grits of sandpaper over and over - coarse, less coarse and medium. He claimed it's much faster than staying with a single grit until flat.

I have not tried this so I can't speak to it personally, but I wish I had known about the method many years / plane blades ago.

Reaaaaaaaaaly. Interesting; it's certainly worth a try, as I won't lose anything but time.

Gee - wonder where I could find a nice sharpening setup?
456163

Made with a fancy Veritas Routing plane no less...
456162

[Evan Van Dyke]

I use 120 grit on a 1m long granite plate. This makes for fast flattening.

Website article here: http://www.inthewoodshop.com/WoodworkTechniques/Lapping%20the%20Backs%20of%20Blades.html

Regards from Perth

Derek

Yeah - a granite lapping plate is on my wish-list. Primarily for flattening out the plane soles, but it would work well for this too. It's a definite option.

Wherever did you find a 1m long lapping plate? Is that a cutout from a sink or something from a granite manufacturer?

[Derek Cohen]

It cost nothing .. zip. It was a cut off from a kitchen bench top supplier. Or use 1/4” thick glass on MDF.

Regards from Perth

Derek

[Eric Rathhaus]

Evan, you could check out David Weaver's youtube channel. He uses a long piece of glass and a homemade jig to flatten the backs of chisels. It makes quick work of this job.

[Tom M King]

A search on these forums should bring up as much information as anyone would need. The good thing about this job is that it only needs to be done once.

[Andrew Hughes]

I think your almost there and could probably start using it. But if you wanted to get a little bit further I suggest adding more pressure across the back of the iron.
You should be able to get there shortly the price will be a worn dmt .
Heres a trick from David Finck to me. I pass it on to you piece of hard maple across the back.

[Derek Cohen]

It is relevant to make a note to oneself when starting out that the effort increases as one progresses.

The reason for this is simply that the early stage involve workin the mountain tops, but progressively one reaches the valley, which is larger. So, the final corners or line behind the bevel are the areas which take the longest to flatten :(

Regards from Perth

Derek

[Evan Van Dyke]

It is relevant to make a note to oneself when starting out that the effort increases as one progresses.

The reason for this is simply that the early stage involve workin the mountain tops, but progressively one reaches the valley, which is larger. So, the final corners or line behind the bevel are the areas which take the longest to flatten :(

Regards from Perth

Derek


Yep - same reason My house doesn't flood at the top of the hill, even when all the neighbors are soaking wet. I am familiar with the theory, but thanks!

I was busy with other things today, but had about an hour to go out and work on it this evening - I didn't notice much of a difference by taking it through all the grits and then back to the coarse. /However/ it seemed to grind much faster when I changed grinding directions on the blade by 90 degrees every once in a while. I assume this is the same reason we scrub in 2 directions - easier to cross-hatch the "hills" of the scratch marks than to keep on grinding the whole surface down. I didn't take a picture, but the size of the dip on the left corner is maybe 1/4 the size it was - making definite progress, and hopefuly another hour or two will take care of it.

I need more exercise anyways - this is a lot of reps on the arms. :)

[Russell Nugent]

You could just use the charlesworth ruler trick on that iron

[Evan Van Dyke]

You could just use the charlesworth ruler trick on that iron

You mean put a back-bevel on it? Suppose I could, but I am ultimately trying to solve some faulty chip-breaker mating issues, so I don't want to confuse things while I'm still learning to sharpen & maintain plane blades.

Good news is that a few more hours on the DMT plates has finished the work on 3 of my plane irons, and the 4th is almost done (#7 iron on the right)
456222

[Evan Van Dyke]

You could just use the charlesworth ruler trick on that iron

You mean put a back-bevel on it? Suppose I could, but I am ultimately trying to solve some faulty chip-breaker mating issues, so I don't want to confuse things while I'm still learning to sharpen & maintain plane blades.

Good news is that a few more hours on the DMT plates has finished the work on 3 of my plane irons, and the 4th is almost done (#7 iron on the right)
456222

[Andrew Seemann]

You mean put a back-bevel on it? Suppose I could, but I am ultimately trying to solve some faulty chip-breaker mating issues, so I don't want to confuse things while I'm still learning to sharpen & maintain plane blades.

Good news is that a few more hours on the DMT plates has finished the work on 3 of my plane irons, and the 4th is almost done (#7 iron on the right)
456222

It isn't a back bevel; that is steeper and is intended to change the cutting angle of the plane.

For what gets called the "ruler trick" (supposedly invented by about a dozen woodworkers, but probably as old as the hills) you just raise the blade a smidge so that the pressure is concentrated on the end of the blade where the blade cuts. There is no need to polish and flatten the whole back, just the end 1/4" - 1/2" or so needs to be polished flat. Only the very edge of the blade cuts, and only about 1/8" of the blade max is exposed in front of the chip breaker. As long as the chip breaker seats well, you are good.

I usually do it by putting most of my finger pressure near the cutting end of the blade. That is often enough to just raise the back of the blade a bit to even out the edge faster.

[Jim Koepke]

Only the very edge of the blade cuts, and only about 1/8" of the blade max is exposed in front of the chip breaker.

That may be good for a jack plane set up to be used as a scrub plane.

There are folks here who would be screaming about their chip breakers being more than 1/64" back from the blade. By some folks figuring, that is even too far.

Search > setting a cap iron < to find an article on Wood Central by David Weaver. The link to the Kato and Kawai video no longer works. It may be available on the web somewhere.

My suggestion is to keep it simple. If a flat back and a decent bevel isn't working, ruler tricks, secondary bevels and cambers are not likely to make things any better.

jtk

[Eric Rathhaus]

Great! I've been down the same road. Glad you finally made it to the end.

[Mark Hennebury]

Do you like making easy hard?
Japanese planes work. Look and learn.
Take a grinder to it, have it done in ten minutes, or spend three days lapping it, your choice.
Japanese handplane blades are hollow ground.
Japanese supersurfacer blades are hollow ground.
Western style plane blades are "Flat" ......and never are! Why? Because even though they don't work, you keep buying them!
People that don't know how planes work, manufacture handplanes.
They manufacture hanplanes because the sell, not because they work.
Think about it, why does it need to be flat for 8"?
If you can answer that then by all means flatten it, but if you cant answer that then do what needs to be done.

[Eric Rathhaus]

Mark are you replying to my post? Not sure what you're on about.

[Russell Nugent]

At what point was anyone talking about flattening 8" of the Iron?

[Jim Matthews]

Mark are you replying to my post? Not sure what you're on about.

You're not the first to be baffled.

[Evan Van Dyke]

I have no problem with a hollow ground iron - but the edge needs to be flat for a properly fitted cap iron. I tried striking the plate to pop my bellied iron into a hollow one, but didn’t work for me. My inexperience may very well be part of that. Not sure why you associate the hollow iron with Japanese planes, when they work anywhere?

Japanese planes are - obviously- quite good. But i have some different ones, that i would much rather put in the time to fix than to throw them out and buy even more.

[Mark Hennebury]

To get the back of your plane blade flat, you need to remove metal from the high spots. You can try lapping it on sandpaper, on a sheet of glass, granite or MDF if you want, that is difficult and time consuming, or you can grind it away, or tap it out with a ballpein hammer on a junk of endgrain hardwood. I tap them them out on a large ash tree stump, It makes for a great anvil. I also grind them out to hollow them a bit, not deep, easy enough to lap out on a 1000 grit stone If you wanted to.
To grind it you can use a tiny pencil grinder with a carbide burr or small grinding wheel, just gently run the burr over the high spots, All of the middle area, the check it by a few laps on your waterstone occasionally.
So you just remove some metal in the middle of your blade, with the grinder. You don't have to remove much, just enough so that when you lap it on your stone it touches around the front for 1/4" or so, and 1/8 on the sides and as far back as you need. You can use any grinder, pencil, die or small disk or even the bench grinder. All you need is to remove a 0.001" in the middle of the blade, so that you have a good flat reference around the sides and front edge. Why try to polish out the middle on sandpaper? Hollow grind it a bit, like the Japanese planes. When you lap one of those blades you are only polishing a tiny bit of metal around the edge, not the whole blade. When your blade is lightly hollow ground it polishes up on the perimeter very fast and right up to the edges for a perfect fit for your chipbreaker. Hollow grinding your blade just removes a tiny bit of metal in the middle of the blade, so you have low spots on the front edge where you have it now.

I do it on my planes and chisels, but then i modify just about everything to make it work better and more efficiently, lots of people have a problem with changing stuff, I don't. I don't buy tools to look at, I want my tools to work, so whatever gets results, I will do.
So what i am saying is look at what you are trying to achieve, look at what you need to do to get there, Throw out the "normal" way. Take a few risks, try something, see if it works.

456322 456323 456324 456325 456326

[Mark Hennebury]

8" 4" 2" how much do you need for the plane to function? Anything more than you need is a waste of time.


At what point was anyone talking about flattening 8" of the Iron?

[Mark Hennebury]

Sorry if I didn't make myself clear.


You're not the first to be baffled.

[Robert Hazelwood]

Diamond plates are not the best to use for this job. They aren't as fast as fresh sandpaper in 80 -120 grit range, and they will get worn out in the process. I'd save them for jobs like flattening/conditioning other stones, where they are very convenient, or random jobs like sharpening carbide or odd shaped tools that would gouge normal stones.

Get something flat and some PSA sandpaper (or adhere normal sandpaper with spray adhesive) and go to town. Change out the paper every few minutes, it dulls fast. Shouldn't take more than 10 minutes this way to get a #4 size iron flat.

A 1 meter long surface plate would be great, especially for flattening a plane sole, but for an iron or chisel back something much smaller works fine.