Flattening a plane sole on a cinder block???

[John Coloccia]

That's been done before,but it's not the same as trying to flatten a cast iron plane sole. I do not see how something like a cinder block,made of an easily worn material would remain flat enough to get the plane flatter than it was to begin with. And,what about larger particles in the block scarring the plane's sole?

I think everyone else is thinking about rubbing directly on the blocks, but my immediate first through was to put some sandpaper down. I was thinking of just using the block as a reasonably flat surface, not an abrasive. I think if you rubbed metal directly on the cinderblock, you'd do nothing but scratch up the metal.

Personally, I use surface plates....sometimes, I use my table saw wing, but I don't have a table saw anymore so oh well I guess I need a bigger surface plate. It's really a special kind of illness that allows someone to get excited over the prospect of buying a flat rock.

[Roy Lindberry]

It's really a special kind of illness that allows someone to get excited over the prospect of buying a flat rock.

We have a couple of 4'x8' Starrett granite surface tables at the lab which are flat +/- 50 μin. I often look at them thinking about how good they'd be for lapping a jointer. I think I have the illness of which you speak.

[Zach Dillinger]

I'm a big proponent of cinder blocks for sharpening stones but I can not see them doing a good job on a plane sole. And you will probably ruin a wooden plane with one. Plus wooden planes are beyond easy to flatten anyway.

[george wilson]

If you ruin your plane on a black granite plate,is it a bad day at black rock?

[John Coloccia]

If you ruin your plane on a black granite plate,is it a bad day at black rock?

LOL. It would be terrible if your favorite plane was slated for the junk pile.