Building the Canadian Semi-Auto STEN

[tiriaq]

Hardened steel is irrelevant to a cutting disc and grinder. Or a carbide drill bit. A common hardware store masonry bit will cut steel if sharpened.
It could be argued that what is acceptable to you is secondary to what is acceptable to the good folks who have classified your guns as prohibited. And it is important that the Mk. V cocking handle function as it should.