Based on how you describe attaching it, I assume you’re talking about the standard [aluminum] model A-34 jigsaw that was designed for use with the 10-ER, and not one of the later Mark 5-compatible [steel] Model 610 jigsaws?
(picture from the A-34 manual)
For the A-34, the bolt that passes through the lower jigsaw casting and into the headstock is obviously about the only thing that holds that accessory in place. So I would guess you have two choices: re-tap the hole to see if there’s enough meat left to reestablish the threads (to do this right, you’d need to disassemble the headstock to get the bearing spacer underneath that hole out of your way), or a jury-rigged method like a ratcheted hold-down strap wrapped around the headstock.
You might want to fix that threaded hole regardless - even if it means tapping to a larger thread size - since that also holds your upper belt guard in place.
Good luck!
