I have an old (1911-1919) 5 1/2 & faced the same problem when it needed a new iron. At the time I wasn't even aware that there had been a change in the blade width so I just ordered a new blade "to suit a 5 1/2", which duly arrived & then I found it didn't fit. I thought I'd been sent the wrong blade, but a few minutes of "research" provided the explanation. So I had no option but to make the new blade fit. In fact, it required much less than 1/16" each side to get the 2 3/8 blade to fit - most old plane mouths are very generously sized width-wise. It took just a few minutes of careful work on the grinder to have my new blade in place.
I would be most surprised if a modern replacement blade won't fit quite comfortably in your plane once you get the width problem sorted. Most of them are around the 0.1" mark (~2.5mm), which is not all that much thicker than the irons of old (most I have measured were between 1.75 to a bit under 2mm), and there is usually plenty enough adjustment available in the frog to accommodate an extra .25mm of blade thickness. You may have a problem with the cam of the adjuster yoke not reaching through the thicker blade far enough to get a good grip on the slot in the chipbreaker. It's mostly not a problem, but the yoke is a cast piece & there is some variation in the length of the cam end, if that is on the short side of average, and if both cam tip & slot are a bit worn, you'll find you have many turns of backlash & the thumbwheel may have to be wound a very long way back to get enough blade extrusion (all this was covered in a recent post..)
Cheers,
Ian
There was probably some variation in mouth sizes. I recall getting both an 8 and 5 1/2 (narrow style). The 5 1/2 needed a lever cap and a blade. That turned out to be terrible. I don't remember what I did about the lever cap, but I think I eventually found one and paid for it.
never found an iron in good shape for a reasonable price and bought one of the LN stanley replacement blades (thinner than the blades for their planes). It could've been a hock, too - long gone now, I only remember the fiscal result.
at any rate hock and LN stanley replacement are about the same thickness and the back of the mouth was a bit coarse, and just the extra couple hundredths of thickness made the plane poor feeding. I ended up filing the mouth just a little as I recall, being surprised it was that tight, and then eventually selling the plane for...
....wait for it. The cost of the parts to make it work well. Something like $80....
....which would be OK if I hadn't actually paid something for the plane in the first place. The seller was less than honest by a mile.
With the 8, I never did find a replacement cap iron for reasonable and got one from LN. It didn't fit because their hole is different than stanley's in length from the edge, and that turned into a humorous debacle (except I couldn't used the plane). They asked me to send the damaged original (which was actually worn through in the middle - the plane was either planing extremely dirty wood or it was used in a fixture) -never seen that before or since - and LN "lost the cap iron on Tom's desk" and it took a while to get it back. When I did get it back, they had made me a custom cap iron for only the cost of one of their stock cap irons and the plane worked a treat.
And I eventually sold that, too. No ill will toward LN - they were nice enough to adjust the original cap iron and give me a custom one for no extra charge, and little pet projects like that are hard to keep track of in a relatively modern boutique production environment. They're unprofitable to say the least, but if anyone has ever gotten a stanley replacement cap iron from LN and it fit their stanley, they can buy me a beer.
From time to time, I will hear how big of a waste of time it is for me to buy tools, or especially to make stanley plane irons, which I can make in 1/2 hour with very limited tools. I suppose if you just want to find one plane that works and stick with it, it is. If I could've made irons or ground cap irons narrower back when I had both of those planes, I'd have spent far less time than I did actually finding replacements.
The cost for an 80crV iron to replace an original stanley would also be about $8.
These days, most of the irons that I see that aren't premium irons are just punched, though. I'd be surprised if their stock plus heat treatment plus finishing cost was half as much as the cost for me to get 80crV. I do use a drill press, die grinder with a carbide burr and files, and then a belt grinder a little (any belt sander would be fine, or even just the files). The plus for irons to be used on planes in the shop is that I can by hand match the slot within a couple of thousandths (and very quickly) by making the slot undersized and then quickly filing to fit the wheel on the lateral adjuster and then the lateral adjustment is tighter even than LNs. '
(the cost to heat treat with thermal cycling is probably about 50 cents and 10 minutes of time, too - tempering takes longer but that's a "set it and forget it" process).
