Learning to Sharpen #8: Flattening the back of plane irons

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Blog entry by Mark Colan posted 09-22-2013 06:12 AM 1529 reads 0 times favorited 4 comments Add to Favorites Watch
« Part 7: Sharpening Class: Cabinet Scrapers Part 8 of Learning to Sharpen series Part 9: Grinding to set a new bevel for a plane iron »

I recently bought used Stanley planes #3, #5, #7. I think only the #5 had ever been properly sharpened, as I could see the factory grinding marks. I doubt the #7 has ever been used.

The #3 in particular had problems: pits and scratches in the base (which required light sanding off a burr), and the blade had pits in the bevel and on the back. The back also had a ding area about 1/2” x 1/4”, basically a shallow depression in the metal.

Learning to sharpen also instructs me on how to select used planes in the future!

The sharpening technique I learned (see notes on the class, earlier in the blog) started with 120, set on top of a piece of glass to which a 320 paper has been glued (only for holding the paper on top in place).

The teacher said sometimes you might go to 100 if the blade has problems. Well, I made only slow progress with the 100, so I tried 80, then 60. I did not want to use 60, because I know it makes deep scratches that you need to work up through the papers to get rid of. But even with 60, it took a long time to flatten the back.

As for the bevel, well, I figured it was a lost cause without a grinder. But I don’t have a lot of skill regrinding the bevel, so I have to learn by trial and error. The good news: I do have the Veritas grinding tool support and blade jig.

-- Mark, hack amateur woodworker, Medford (greater Boston) MA

4 comments so far

View Tugboater78's profile


2743 posts in 2192 days

#1 posted 09-23-2013 12:57 AM

Flattening backs of old irons has been my bane since I started collecting/buying old planes.. some have had some major abuse, others are just plain horrible.

-- "....put that handsaw to work and make it earn its keep. - summerfi" <==< JuStiN >==>=->

View bobasaurus's profile


3452 posts in 3184 days

#2 posted 09-23-2013 02:47 AM

Flattening blades/chisels/plane soles/etc is a huge time-consuming chore. I’ve tried sandpaper on granite, steel lapping plates, diamond stones, and recently a belt/disc sander. The sander makes really quick work of it, but it’s easy to round corners and overheat steel… now that I have a knack for it I use it a lot (220 grit belt seems to work the best). My next choice would be the diamond stones, though mine has now worn down and become less useful for the rough lapping.

-- Allen, Colorado (Instagram @bobasaurus_woodworking)

View Woodknack's profile


11626 posts in 2380 days

#3 posted 09-23-2013 05:14 AM

If they are really bad I start with 80 grit on the disc sander. The finer the grit the faster it heats up so not only do you get flat faster but cooler as well.

-- Rick M,

View Mark Colan's profile

Mark Colan

211 posts in 2845 days

#4 posted 09-23-2013 05:26 AM

It WAS time consuming. This is also my first time doing it, so it’s taking longer to work out my technique.

I figure that I won’t be doing a flattening job to this extent more than once for these blades. There are more blades to be done, but these were the biggest and oldest.

If I had a stationary power sanding tool, I might try that, but trying to get my handhelds in a fixed position seems problematic.

-- Mark, hack amateur woodworker, Medford (greater Boston) MA

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