Pretoria-based group formed in 1984 which was essentially Piet Botha with various back up bands. In 1984 the line-up was Piet Botha (guitar, vocals), Boet Faber (guitar), Eric Birkenstock (bass) and Jan Maloney (drums).
In 1985 the group line-up almost complete changed to: Piet Botha (guitar, vocals), Paul van Eden (guitar, vocals), Paul Barnard (bass) and Derek Riley (drums).
Following the death of Derek Riley another dramatic line-up change in 1988 saw Piet Botha (guitar, vocals) playing with Paul Vantoon (guitar, vocals), Lani van der Walt (guitar), Tony Erasmus (bass) and Janny Gallagher (drums).
They broke up in 1990 but in 1992 reformed with Piet Botha (guitar, vocals), David Codling (guitar), Robert Nel (bass) and Findlay Malherbe (drums).
In 1993 Lowell Jeffrey replaced Nel on bass.
Jack Hammer released several albums: Jack of all Trades (1987), The Judas Chapter (1990), Ghosts on the Wind (1994), Death of a Gypsy (1996), Bootleg (2001) and Highway 13 (2008).
By the time of Highway 13 their line-up had changed to: Piet Botha (guitar, keyboards, harmonica, vocals), Jonathan Martin (guitar, vocals), Tertius du Plessis (bass) and Paul van de Waal (drums).