The board and pins you used to develop the perspex prototype can be reused to get the steel spring and blade working but, before attempting to turn the steel blade on the board, put one of the perspex sides down first to support the pins or they will tear out of the wood
1. Using your perspex prototype as a template, cut your blade and spring out of steel and drill the holes.
2. Carefully file up to your scribe lines, leaving a little material for adjustment around the tip of the spring and the tang of the blade.
3. Put them on the board with the blade in the open position and fit the spring to the back square:
4. With the blade in the closed position, shape the kick of the blade:
5. Heat treat the spring then put it back on the board and check the open and closed positions still work (it might warp as you heat treat) then gently round the corners of the tang until you achieve the opening and closing action you require (you might want to bend the spring a little to put more pressure):
6. Cut the sides out of sheet metal thick enough to take the pressure of the spring without further scale material - 2mm brass is good for this job then assemble the knife within these sides and retest the opening and closing action, taking it apart to refine the shape as necessary.
7. Make the final adjustments to the overall shape of the handle and blade so they look as you wish both open and shut:
