change the formatting of the chapter

Question

I am trying to change the formatting of my chapter. The class i am using is report. I want it to be bold centered. I used the following but no effect. .

\renewcommand{\@makechapterhead}[1]{%
\vspace*{50\p@}%
{\parindent \z@ \raggedright \normalfont
\hrule
\vspace{5pt}%
\ifnum \c@secnumdepth >\m@ne
\huge\scshape \@chapapp\space \thechapter
\par\nobreak
\vskip 20\p@
\fi
\interlinepenalty\@M
\Huge \scshape #1\par
\vspace{5pt}%
\hrule
\nobreak
\vskip 40\p@
}}
\renewcommand{\@makeschapterhead}[1]{%
\vspace*{50\p@}%
{\parindent \z@ \raggedright
\normalfont
\hrule
\vspace{5pt}%
\interlinepenalty\@M
\Huge \scshape #1\par
\vspace{5pt}%
\hrule
\nobreak
\vskip 40\p@
}}

Answer 1

The following MWE takes your code as the starting basis. I've provided examples of both numbered and unnumbered chapter headings. The main changes, relative to the code you provided, are: (i) the two \raggedright directives have been replaced with \centering directives, (ii) the three \scshape instructions have been replaced with \bfseries instructions, and (iii) there's a little bit more vertical whitespace below the first \hrule and above the second \hrule statements. (Your code provides only 5pt of vertical separation, but I think that 12pt and 10pt, respectively, may be easier on the reader's eye. This is obviously a subjective decision and you should feel free to tweak the code further.) Hope this is what you're looking for.

\documentclass{report}
\usepackage{lipsum} % for filler text
\makeatletter
\renewcommand{\@makechapterhead}[1]{%
    \vspace*{50\p@}%
    {\parindent \z@ \centering \normalfont
    \hrule
    \vspace{12pt}%
    \ifnum \c@secnumdepth >\m@ne
        \huge\bfseries \@chapapp\space \thechapter
        \par\nobreak
        \vskip 20\p@
    \fi
    \interlinepenalty\@M
    \Huge \bfseries #1\par
    \vspace{10pt}%
    \hrule
    \vskip 40\p@
}}
\renewcommand{\@makeschapterhead}[1]{%
    \vspace*{50\p@}%
    {\parindent \z@ \centering
    \normalfont
    \hrule
    \vspace{12pt}%
    \interlinepenalty\@M
    \Huge \bfseries #1\par
    \vspace{10pt}%
    \hrule
    \vskip 40\p@
}}
\makeatother
\begin{document}
\chapter{Hello There!}
\lipsum[1]
\chapter*{Good Bye}
\lipsum[2]
\end{document}

First the numbered chapter style:

Second, the unnumbered chapter style:

Answer 2

As suggested in a comment, you can use the sectsty package:

\documentclass{report}
\usepackage{sectsty}
\usepackage{lipsum}% just to generate some text

\chapterfont{\centering}

\begin{document}

\chapter{Test Chapter}
\lipsum[4]

\end{document}