# Align several pie charts in table

I want to align several pie charts of different sizes in one table. Specifically, I want that these pie charts are horizontally and vertically aligned such that the centers of the pie charts are on one horizontal and vertical line, respectively. So far I was not succesfull. Any ideas?

%
% Examples for pgf-pie, by Yuan Xu
%
% Based on the manual from:
%
\documentclass{article}
\usepackage{fullpage}
\usepackage{pgf-pie}

\begin{document}
\maketitle

\begin{table}[h!]
\centering
\begin{tabular}{m{2cm} c c}
\hline
& A & B \\ \hline

A                    &
\begin{center}
\begin{tabular}{m}
\begin{tikzpicture}
color = {green, gray, red}, sum=auto]{1/, 5/, 1/}
\end{tikzpicture}
\end{tabular}
\end{center}&

\begin{center}
\begin{tabular}{m}
\begin{tikzpicture}
color = {gray}, sum=auto]{2/}
\end{tikzpicture}
\end{tabular}
\end{center}\\

B                    &
\begin{center}
\begin{tabular}{m}
\begin{tikzpicture}
color = {gray}, sum=auto]{3/}
\end{tikzpicture}
\end{tabular}
\end{center}&

\begin{center}
\begin{tabular}{m}
\begin{tikzpicture}
color = {gray, red}, sum=auto]{2/ , 2/}
\end{tikzpicture}
\end{tabular}
\end{center}

\end{tabular}
\end{table}
\end{document}


Currently it looks like that:

It should look loke this:

With clipping to a specific area it works:

\documentclass{article}
\usepackage{fullpage}
\usepackage{pgf-pie}
\usepackage{array}
\usepackage{ragged2e}
\newcolumntype{M}[1]{>{\Centering}m{#1}}
\begin{document}

\begin{tabular}{c | M{2.5cm} | M{1.75cm} |}\hline
& A & B \\ \hline
A   &   \frame{\begin{tikzpicture}\clip (0,0) circle (1cm);
color={green,gray,red},sum=auto]{1/,5/,1/}
\end{tikzpicture}}%
&  \frame{\begin{tikzpicture}\clip (0,0) circle (0.5cm);