At the time of social book marking title like for example:Packaging Machinery will be used in keyword ,is it usefull google crawl ?

Here the title is of two words and this is also a keyword which have some searches in the Industry. You can use this title also as the keyword in the tag section but you have to check the keyword density as well. If your content is of 50-60 words then you can use your targeted keyword for twice as percentage ( 3-5% ). So there will not be any problem if you use this title "Packaging Machinery" again in the tag section.