There is a useful plugin for welding called Constraint Editor (by Wunder_Wulfe) try it.
How to use it? - just select all the parts u want to weld and click on plugin
If you don’t want to install a plugin you can also use this script. It’s very simple: insert the script in the root (therefore on the Handle part), then insert all the parts to be joined inside the Handle. The script will take care of the rest.