# Custom font family with siunitx

I'm trying to set some relatively large tables in my document. I used fontspec to create a new font family, which I use only to set tables. Specifically, I'm using the Bell Centennial font to set my tables.

I've defined the font family with:

\newfontfamily\bellcentennial[
Path = fonts/BC/ ,
Extension = .otf ,
]{BellCentennialStd}


My problem is, I have no idea how to setup siunitx to use the \bellcentennial font family. Using detect-family just gives me the standard math roman font.

This should be an acceptable MWE:

\documentclass{article}
\usepackage{fontspec}
\usepackage{siunitx}

\newfontfamily\bellcentennial[
Path = fonts/BC/ ,
Extension = .otf ,
]{BellCentennialStd}

\begin{document}
\begin{table}
\centering
\begingroup
\bellcentennial
\fontsize{6pt}{6pt}
\selectfont
\begin{tabular}{r S S}
\multicolumn{1}{c}{\textbf{Label}} & \multicolumn{2}{c}{\textbf{Numbers}} \\
Foo & 1.2 & 3.4 \\
Bar & 5.6 & 7.8 \\
Baz & 9.0 & 12.34 \\
Qux & 56.789 & 0.0 \\
\end{tabular}
\endgroup
\caption{The most wonderous of tables.}
\label{tab:tableytabletable}
\end{table}
\end{document}
\end{table}


Of course, unless you have the Bell Centennial fonts and use the same folder structure as I do, you are going to have to redefine the definition of the \bellcentennial font family to work locally.

I'm sure I'm missing something obvious with setting up siunitx but I'm unsure of where to start looking.

Redefine what text-rm does.

I changed the font with a very distinctive one, not having yours.

\documentclass{article}
\usepackage{fontspec}
\usepackage{siunitx}

\newfontfamily\bellcentennial[
%    Path = fonts/BC/ ,
%    Extension = .otf ,
%]{BellCentennialStd}
Ligatures=TeX
]{Futura}

\begin{document}
\begin{table}
\sisetup{detect-all,text-rm=\bellcentennial}
\centering
\begingroup\fontsize{6pt}{6pt}\bellcentennial

\begin{tabular}{r S S}
\multicolumn{1}{c}{\textbf{Label}} & \multicolumn{2}{c}{\textbf{Numbers}} \\
Foo & 1.2 & 3.4 \\
Bar & 5.6 & 7.8 \\
Baz & 9.0 & 12.34 \\
Qux & 56.789 & 0.0 \\
\end{tabular}

\endgroup

\caption{The most wonderous of tables.}\label{tab:tableytabletable}
\end{table}
\end{document}