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.

IMG_1734.HEIC.jpg

[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/Woodwor...%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?
IMG_1738.HEIC.jpg

Made with a fancy Veritas Routing plane no less...
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[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/Woodwor...%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)
IMG_1758.HEIC.jpg

[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)
IMG_1758.HEIC.jpg