Over the last two decades, quality of products and service has become a cardinal priority for business organizations irrespective of their size and type. Accordingly, this research work makes an assessment and improvement of product quality on Small and Medium Scale Metal Manufacturing Enterprises located at Mizan-Aman town, Southern region of Ethiopia. A brief introduction is given on the fundamental concepts of quality with reference to recent literature. The research was mainly carried out through direct observation on the enterprises, data collecting employing questionnaire survey and interview, analyzing the data, result and discussion of the analysis and conclusion. To undertake this research a sample size of 15 Small and Medium Scale Metal Manufacturing Enterprises were chosen. The enterprises are engaged on manufacturing furniture items, construction items, grinding agriculture tool, maintenance work, modification spare part etc. Among those enterprises six of them which have engine lathe machine were specifically taken for the case study of maintaining grinding flour mill shaft is one of the major works to be performed by the enterprises day to night. The improper maintenance of the shafts on the engine lathe machine, too much queue waiting for maintenance, and failure of them within short period of time is the critical problem with them. In the case study, those enterprises which have engine lathe machine for maintenance of grinding flour mill shaft were analytically examined. According to the findings from the questionnaire and case study, improper uses of cutting speed, improper cutting parameter, improper machine alignment and inadequate knowledge about limit, fits, and tolerance between the mating parts or applying inappropriate and random dimensioning, improper welding process, improper maintenance processes and sequences are the factors for the improper maintenance of the shaft. These factors could contribute for the improvement system of product quality. Furthermore, the study revealed that the enterprises should give due attention for their product quality problem through giving and preparing continuous training for employees. Since most of the employees of SMMEs are graduated from TVET Institutes, evaluating institutes training result should also be a critical factor for the product quality improvement effort. Besides, all type of grinding flour mill which work on electricity, wind, water and petrol have similar maintenance shaft regardless of the materials used i.e. coffee, raise, wheat, maize, teff, beans etc. The finding of this study, therefore, can be used as a lead for future research works in the field through evaluating the number of grinding mill in each Woreda, Zone, and State.