Clapper lock for slotting with a shaper

[Toolmaker51]

My shaper is great for a lot of stuff but finishing cuts and internal slotting have been difficult because the clapper is small and light.
...Here are my slotting tool holders-the short one replaces the tool post and the long one fits my simplified copy of Art Volz’ multiple angle holder.

Long ago, my first gig often placed me at a heavy 24" G & E shaper. Mostly made Vee'd spot-welding jaws for wire. Whatever grade of copper, was tough and abrasive on HSS bits. We had two clappers, standard of course, the second one fitted with a die spring and restrained by a through bolt to base. It allowed tool retract on backstroke and snap into cutting position immediately. Base had 2 bearing balls in pockets. One insured clapper base was positioned fully to one side [even though minimal clearance] of the box. Other did same but front to back and not spring loaded mating first, then side to side action occurred. That 2nd clapper and box were shopmade who knows how long ago.