Side plates and axle pin?

I want my next build to have side plates. What's the best method of attaching an axle pin? I'm thinking of threading one side with a 4mm tap then screwing a mild steel 4mm bolt through sticking out about 3 mm. I'm then going to heat the stub and hammer it flat like a rivet to finish the external side. The roller nut will slide over the bolt with just 2-3mm protruding so when I fit the second plate the bolt will sit in a divet hole on the inside of the plate. I'm sure this will work But I do notice some builds (Geezers) with no evidence of an axle pin. Am I missing a far simpler/ better method?

Geezer here: on bows without metal lockplates (leather, horn, wood, whatever) in the central European style, I secure the nut with a 'nussfaden' bridle of cord. It looks like some bows may have used a piece of malleable wire, or cable strung thru the nut (roller) and tied in place with cord.  Bows with metal lockplates, I ususally fit a bit of brass wire thru the roller, thru the sides of the socket and held in place with the lockplates themselves. Sometimes I use two brass escutcheon pins (preferably 16 gauge) pushed thru from both sides.  The point is to keep the roller from falling out... but the wire or pins are not intended to bear any load.  The original Padre Island bow (Spanish @ 1500) has an axle hole thru the roller but there is no sign of a keeper-pin, wire, cord.... nothing at all, and no hole to accept one.  If the socket is a fairly close fit, and deep enough (2/3 of the roller-diameter) the nut should stay in place without support, but there's always a chance it may fall out.  That's why I always fit some sort of keeper.  You could fit a stronger axle to center the nut, and if it's well enough supported, it should increase the speed of nut-rotation, but eventually, the pin will probably bend... it might create problems getting it out for replacement.  Geezer.
ps:  Payne Gallwey's pattern has a fairly reasonable solution (The Crossbow, or The Book of the Crossbow) But of course PG specifies a close-fitting iron socket that is shallower than optimal.  (3/5 buried)  If you make your nut socket close-to or in excess of 3/4 buried, you won't be able to remove the roller from the top of its socket.  You'll have to go in the side.  Geezer.