The availability of spare components for Stanley/Bailey planes in progressively uncertain and intermittent.
At The Wood Works we have supported supply of these spares to the component level for over 30 years.
These back iron or chipbreaker screws are made for us in Sydney in stainless steel by a specialist machinist who managed to crack the code for the proprietary thread used by Stanley and widely copied by clone makers.
The screw has a 6mm thread projection - slightly longer than the Stanley option - in an effort to accomodate thicker blades.
If you wish to upgrade planes to a thicker gauge than the standard Stanley blade be mindful of the fact that you may have to file the mouth open unless you have a model with an adjustable frog.