Tricky twist-fillers and button fillers

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When repairing pens I come across all sorts of difficulties. Except for stuck nibs and feeds on any pen, I struggle with twist fillers.

Swan models and others have a space for the presser bar in the section you fit the ink sack too. It can be very tricky to get the parts in correcly, for the twist filling action to actually work. I have manage to bend a new presser bar out of shape, and the ink sack has some how taken a twisted form. This one I'm now mailing to a repair guy.

The other problem has been a no particular brand pen with the basic button filler parts, section - ink sack - presser bar, and push button on top. There isn't any space in the section to secure the presser bar in place. Is that a normal feature on button fillers? It looks like the botton of the presser bar is prone to puncture the ink sack? There's probably some basic element to it I don't see.

Anyone who recognise the problems?