solder on sight glasses

[CH3CH2OH]

What techniques have you guys used to solder on your sight glasses??

cut hole first? cut hole after? do you clamp them in place? solder from the inside or outside? etc

this is the last step in the build and for me is the most intimidating so I've saved it for last

any pointers would be greatly appreciated so i don't end up with an ugly mess!!!

[googe]

Ive always sat the glass flange on the tube, heat from outside, solder from inside. Cut the hole after wards. Once you've done it once its a breeze, just make sure the flange is nice and flat for the glass to sit on, belt sand it or file it flat, just makes life easy, oh, and don't screw em on to tight. Good luck.