I have a single speed mountain bike that i buit up a few months back. in its current state its ridable, but not finished. Its an 80's trek steel frame, with a mixed matched (but really pretty nice) wheel set, and a road master POS fork. Ive been looking into fork options for a while, at first i wanted a suspension fork but its one inch threaded blah blah blah. anyway, point is, I've settled on getting an old 26" bmx fork. They're cheap and strong. however, both of my wheels have disc hubs on them, right now I'm using a cantilever brake on the back and there is no brake on the front. I was wondering if it is possible to weld disc brake tabs on the front fork. If so, is it safe? if not, would it be a wiser option to weld tabs on the rear end?

this is what I'm thinking in my head:
https://www.ebay.com/itm/Landrace-CR-...ht_1398wt_1114

#1 Chrome has to come off, first, You will haver to grind thry it , to base metal to braze on the tabs.

seek out one thats painted instead, perhaps?
rear end , you will have to add a cross brace behind the Disc tabs to join the 2 stays in a small triangle .

In both cases you need to get clear on the ISO standards for location for both
and probably make Jigs to hold the parts in place, accurate locations,
while you are brazing them ..

Got a TIG welder? that will do the job of attaching things,
still need the locations spot on.

do you know of any well illustrated tutorials or well documented projects here on the internetzz? pictures usually help me with these kind of things hah

It would be a whole lot of fab time ($$$) to make the brake tab that would fit that fork. Sure would be a whole lot easier and cheaper to start with the right fork to begin with.
Ask for old forks at some of the more established shops in your area or put up a wanted ad in some of the online forum's classifieds. I'll bet you find a fork pretty easily.

If your bike has horizontal dropouts in the rear, it will be very difficult to get the rear wheel aligned correctly every time. If you look at the disc braked single speed options out there you will tend to find that they have vertical dropouts with either a single speed chain tensioner or an eccentric bottom bracket.