A useless bit of information.
Srings , washers , bolts are what you need for soldering internal bushes
Spring larger diameter than bush outside
Bolts to fit bush thread .
Washer to fit bolt under head and larger than spring .
Method
After cleaning and ready to solder bush in place
Insert bush with ring of solder
Place washer on bolt then spring ,screw bolt into bush .
Spring is compressed between washer and boiler surface thus holding bush is place
It will also work when removing endcaps and not wanting internal bushes to drop off .
Cheers
Dennis
Dennis come on mate im not that clever i much prefer to make life difficult, it gives me something to write about

my way is so simple but acrobatic...Steve