Bowling machine balls are a No No for knocking in bat blades.
I got the same advice from Laver, don't use Bola fed balls for bat knocking. I stand by that suggestion as Bola balls do hit the bat a late harder and also at the same/close proximity of the same spot over and over again which could lead to early delamination in a new bat.
Best way to knock a bat in order of effeciveness:
- Light mallet work followed by old, soft leather balls in nets - takes longer but an even bat knocking experience.
- Mallet work - slow and gentle to heavy.
- Mallet and machine knocking ( I have to say that my machine knocked bat pings incredibly well )
- Buy a Kranzie ($$$$) and don't knock , they are pretty good to go out of the box.