We report large scale quantum mechanical calculations for the ground state energy E-0 and for the dissociation energy D-0 of the HF dimer on the SQSBDE potential energy surface of Quack and Suhm. A value of 4593.13 cm(-1) is obtained for E-0 by a large scale variational basis set expansion and confirmed by very accurate quantum Monte Carlo calculations giving E-0 of 4593.15 +/- 0.03 cm(-1). The noticeably higher ground state energies computed in previous variational studies are explained by the use of suboptimal HF eigenfunctions. The new estimated value of D-0 is 1058.00 cm(-1).