Tom states the following:

[Caveat re: Timing Pulley Failure [Tip from Tom Irwin:] Here one problem to watch out for... B230 lower timing pulleys have a little 'nib' extrusion that does the work of a keyway/shaft. It is a cast part and it is delicate. In the old days we used to fix a large socket and breaker bar over the pulley bolt, wedge it against something solid and whap the starter over to break loose the bolt... DON'T DO IT! That little key/nib will break off or weaken so it breaks later and ALL your accessory drives (alt/ps/ac/etc) stops spinning. Oh yah! that little chunk o'metal is special order and about a hundred bucks! Any bolt removal technique that relies on "whapping the starter", jamming the ring gear, or using an air wrench on the center bolt, may cause this key to break off. Get the right tool (Volvo 5284) and restrain the pulley


Can someone further explain this? If I understand the nut he's referring to it's this. On second thought though it can't be that type of nut.

Does anyone understand why a crank pulley tool would eliminate snapping the key or why removing using the air/ring-jam/starter method would break it.

BTW, does anyone have a pic of the nut Tom's referring to?

--
Norm Cook Vancouver BC; 1989 745T 204,000KM