I bought a mh41 which i am very happy with, thanks m4d m4x, anyway i let it get damp and i got it working again with easy start to remove corrosion so the led dedomed from the ether.
then i took it apart to take out the old dome and I noticed there was no screw holding the mcpcb down, just an empty hole.
can I keep using this light like it is with the reflector tightening the mcpcb or do i need to buy a screw and if so , where and what type.
Also i was wondering is it possible to buy a 4 inch compression fitting and fit a reflector behind the nut, then add reducers down to a 3/4 or 1 inch inch pipe to make a whole flashlight from brass or copper plumbing fittings.
Hi, I think it’s okay as long as reflector pushes the MCPCB down, so it’s not hanging in the air 
People have done stranger things to make flashlights from scratch, you just have to find parts that will fit together. The biggest hurdles in most of my projects seem to be focusing, driver pockets (limited machining ability/tools) and securely fastening switches for the same reason.
A lot of the newer lights coming out have screw in retaining rings for the driver as well as the switch. Home built stuff is awesome but it usually presents quite a few challenges. Post pics of your project if you give it a go!