TWIST ! The ones that are pre-assembled by Aixiz (or whomever their source is) are glued together with a funky white-silicone based glue....it takes some good force to separate them.
If you have a drill (or a lathe) with a 3 jaw chuck hold the front end lightly in that, then use a pair of pliers with a piece of rag in the jaws on the back end holding tight enough to undo it but not so tight that you mark or squash it.
You could do what rog said, you could also drop it in boiling water and let it sit for a while, (without the lens asembly of course) then take it out and grab a rag or something to hold it so it doesn't slip. Then twist as hard as you can.
I think using pliers would be easier than having to heat the module.
Oh, you actually want to use the 5mW LD. ;D Most of us here completely destroy that LD so we can place a high powered laser diode in there.
Just use some pliers, a rag, and twist.
Are you turning it the right direction? Just joking. Try wrapping some grippy cloth or paper around the outside of both the head and the body and get two pairs of pliers. Then grip hard and twist. Use leverage to your advantage!
I use a couple of clothes pins - the wood kind.
That gives pretty good grip plus prevents scratching.
Just put one on each end of the module, then use pliers / vise grips / vise over each clothespin. As you twist, if one of the clothespins starts to slip just squeeze harder on the pliers.
Works every time for me.
If you can't keep it from slipping, use sandpaper to rough up the clothespin surface. Or, a little piece of moist but not wet chamois cloth in there will give it great grip.
in the photo below, I didn't remove the labels from the module but it will all go easier without the labels (I didn't really want to disassemble this one).
I remove the danger sticker first so I can re-use it on my new burner when I'm done. I usually use vise grips and pliers because it twist really easy and doesn't scratch plus I don't care if it does anyway. I saw the title of this thread and thought "OHH NO!" ;D Putting the new diode in the place of the old one (once you get that out) is the most challenging.
It took couple hours baking it in the car during afternoon and twisted it off with an anti slip mat.
on a side note,I seem to have lost the spring(the one fitted with the lens) during disassembly.
is the spring important?