Is possible to join/glue 2 or more glyph and change orginal font?

For example I need 'a'='a' and 'dot' above or under or k=f+k but f is small and up than small k.

And change orginal a and k? here example:

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(Lua/Xe/pdf)(La)TeX are not font design programs, you may want to look at programs like FontForge. – morbusg May 17 '13 at 19:03
I'm not ask a NEW font but glue 2 or more glyph. ugly example: ą=a+cedila I need some letter to change normal letter s = s+ small o inside s etc. – Pankracy May 18 '13 at 11:20

You may be able to achieve your goals using TeX's "primitive" commands \kern, \lower, and \hbox. These commands work the same way under luatex and pdftex.

% !TEX TS-program = lualatex
\documentclass{article}
\usepackage{fontspec,amsmath}
\newcommand\normalk{\text{\sffamily k}}
\newcommand\kf{\text{\sffamily k\kern-0.3em\lower-0.7ex\hbox{\tiny f}}}
\begin{document}\pagestyle{empty}
$\normalk=\kf$
\end{document}

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ok, but what i can convert my \kf command into normal k letter? – Pankracy May 18 '13 at 20:31
@Pankracy - Please see the edited version of my answer for both a "normal k" and a k with a small f on top. – Mico May 19 '13 at 0:48
The kerning is wrong: \normalk x = \kf x. Maybe: \ooalign{\hss\kern.05em\lower.7ex\hbox{\tiny f}\hss\cr k} or \rlap{\kern.18em\raise.7ex\hbox{\tiny f}}k – Qrrbrbirlbel May 19 '13 at 1:11
@Qrrbrbirlbel - you may be right. :-) – Mico May 19 '13 at 1:47
editer version is not good. Hyphenation not working, ugly described. I need normal k. this is meaning normal k not \kf or other not normal k. I need write word 'kot' 'kociołek' etc. NOT '\kfociłek' '\kfot' – Pankracy May 19 '13 at 12:06