  Lattice QCD calculations using gauge smearing for fermion kernels are
computationally efficient. Hypercubic blocking (nHYP smearing) has been shown
to reduce scaling errors. In this work we use an improved action for $N_f=2$
QCD, based on the L\"uscher-Weisz gauge action and clover-improved Wilson
fermions with nHYP smeared gauge links. We perform a parameter scan in the
region with lattice spacing between $0.066 \mathop{\hbox{fm}}$ and $0.115
\mathop{\hbox{fm}}$ and pion mass between $207 \mathop{\hbox{MeV}}$ and $834
\mathop{\hbox{MeV}}$.
  We determine the lattice spacing and pion mass as a function of the bare
coupling parameters ($\beta$ and $\kappa$). The results are obtained from
twenty-two ensembles on a $24^3\times 48$ lattice to percent level in
statistical accuracy. The finite-volume effects for these ensemble are at the
sub-percent level. From these measurements we produce easy-to-use
parameterizations to help tune simulations with this action. The lattice
spacing is fixed using a mass-independent procedure, by matching observables in
the chiral limit. We also provide a parameterization for the chiral
extrapolation which is universal and should hold for all discretizations of
$N_f=2$ QCD.
