Every vacumatic filling unit i'm removing for cleaning and renovating (only my own pens), the retaining collar the part with 2 sets of threads is loose from the inner collar. Why is this???? What do the experts use to reattach???

If I'm understanding your question, you're concerned that the blind cap nipple - the part with the threads that screw into the barrel, and onto which the blind cap screws, is separated from the cone that holds the diaphragm in place.

The answer is that it's supposed to be. The blind cap nipple must be able to spin freely on the cone. If it doesn't, it will bind on the diaphragm, then twist and chew up the end of the diaphragm, and you'l have a leaking pen.

I knew it, THANKS Ron, as always the man to deliver Really i've just started on some of my vacs and enjoying the challenge for some reason i got it into my head those 2 parts should be attached and on describing to another fpner he said they should be together but i guess he misunderstood my explanation.

Hi Ron, Which is correct.......

Your filler unit is fine. It looks really clean as a matter of fact. Good one!

The black part is the blind cap nipple, and the "white" aluminum part is the cone. Below that you have the pellet cup. These fillers have a spring that sits in the cone. The spring is held in place by the cone, and is attached to the filler's plastic rod just behind the pellet cup.

Inside the barrel there is a tapered seat. The open/folded back end of the diaphragm sits on the cone, and is wedged between the cone and the tapered seat in the barrel, which incidently keeps the cone from sliding down the barrel.

When you reinstall the filler unit, the blind cap nipple screws into the barrel and goes over the cone, firmly clamping the diaphragm and cone on the seat. You are of course turning the blind cap nipple, so it has to rotate freely over the cone. If it doesn't, the cone will rotate too, and in the process grab the diaphragm and try to turn that too, which is what chews up the diaphragm.

Sometimes the back end of the cone (the squared off stepped end) and the inside of the blind cap nipple are covered with corrosion. You have to clean this off before you can reinstall the filler.

Ron, Ron, Ron, your a star superstar. The penny has finally dropped Thankyou, for sharing once again your expertise