The node’s border is a path, you can use the same options for a \path
, e.g. ultra thin
, thick
, very thick
, and so on:
\node[circle, draw=blue!80, thick, inner sep=0pt, minimum size=12pt] (1) at (0,0) {1};
The line width
key works as well:
\node[circle,draw=blue!80, line width=1mm, inner sep=0pt,minimum size=12pt] (1) at(0,0) {1};
All predefined line widths are
\tikzset{
ultra thin/.style= {line width=0.1pt},
very thin/.style= {line width=0.2pt},
thin/.style= {line width=0.4pt},% thin is the default
semithick/.style= {line width=0.6pt},
thick/.style= {line width=0.8pt},
very thick/.style= {line width=1.2pt},
ultra thick/.style={line width=1.6pt}
}
Code
\documentclass[tikz]{standalone}
\begin{document}
\begin{tikzpicture}[
every node/.append style={circle, draw=blue!80, inner sep=0pt, minimum size=12pt}]
\node (1) at (0,0) {1};
\node[thick] (2) at (1,0) {2};
\node[line width=1mm] (3) at (2,0) {3};
\end{tikzpicture}
\end{document}
Output

I don't really get the question so I hope this is what you wanted. If you include a full document (such that we copy paste and see the problem on our systems) things are much more easier.
Here, you can change the default setting within a scope but your block
style had a node distance
which was resetting every time it is issued. I've made it 2mm such that we can see the difference easier.
\documentclass[tikz]{standalone}
\usetikzlibrary{arrows,shapes.geometric,positioning}
\begin{document}
\begin{tikzpicture}[decision/.style={diamond, draw, text width=4.5em, text badly centered, node distance=3.5cm, inner sep=0pt},
block/.style ={rectangle, draw, text width=6em, text centered, rounded corners, minimum height=4em, minimum height=2em},
cloud/.style ={draw, ellipse, minimum height=2em},
line/.style ={draw,-latex'},
node distance = 1cm,
auto]
\node [block] (1st) {1st};
\node [block, right= of 1st] (2nd1) {2nd1};
\begin{scope}[node distance=2mm and 10mm]%Here we change it for everything inside this scope
\node [block, above= of 2nd1] (2nd2) {2nd2};
\node [block, below= of 2nd1] (2nd3) {2nd3};
\node [block, right= of 2nd1] (3rd1) {3rd1};
\node [block, above= of 3rd1] (3rd2) {3rd2};
\node [block, above= of 3rd2] (3rd3) {3rd3};
\end{scope}
\node [block, below= of 3rd1] (3rd4) {3rd4};
\node [block, below= of 3rd4] (3rd5) {3rd5};
\path [line] (1st) -- (2nd1);
\path [line] (2nd1) -- (2nd2);
\path [line] (2nd1) -- (2nd3);
\path [line] (2nd2) -- (3rd3);
\path [line] (2nd1) -- (3rd1);
\path [line] (1st) -- (2nd1);
\end{tikzpicture}
\end{document}

Best Answer
This is a pure calc alternative in case
dimline
doesn't allow you to do that. (I do not know whatdimline
does.) This is an updated answer in which I try to address your comments. It comes with a decorationindicate dimensions
, which has one argument, the label. All distances and other parameters are stored in pgfkeys. Drawing the line plus all the dimension lines and perpendicular lines boils down toHere is the code with many examples.