A couple of years ago Lie-Nielsen stopped production of O-1 tools. I can understand from a bottom line standpoint but....There is that damn but again....Some of us really do not like to use A-2 cutters. I like the LN planes, they are very well made if a little heavy, I can live with heavy. Living with A-2 cutters, not so much.
So of course Hock and Lee Valley come to mind, they both make very good O-1and LV makes PM-11 irons as well, there is just one tiny problem. Both Hock and LV plane irons are just a silly mm thinner than LN's irons. That difference keeps either from mating with the LN frog. The LN depth adjuster has a steep slope and to mate with the cap iron requires a cutter of LN's thickness, other wise it will not let the cutter/chip breaker mate with the frog.
I've gone back and forth, sell all my LN planes but I like 'em except for the irons. Live with A-2 cutters, OK I've tried....It's like a bad marriage, you can make it work but is it worth the effort. What to do, what to do. I've had a Clifton iron on back order for months now (Its specs show it is the same thickness as the LN) but so for no joy.
I finally did a little red neck engineering and enlarged the depth adjustment slot on a Hock chip breaker and installed a LV O-1 iron with the modded Hock chip breaker in the LN #4. It works, the iron/chip breaker mate with the frog and there is little "slop" in the depth adjuster.
I'll live with the mod for a few weeks and if there are no problems the rest of the LN's will get the same adjustment.