I was just going through this lovely blog I recently started following called girls and bicycles, and came across this post.

Innovative uses of a bicycle - I (Sharpening knifes)

Mr. Kishan Yadav- the 'Dhaar Wala' (knife sharpener) came to our doorstep today morning. I had two knifes which needed sharpening so I went out to get it done.
As I shot this video, I noticed how a buffing wheel has been attached in the top tube of his simple bicycle. It is connected to a circular strip on the back wheel. He pedals his bike while on the stand and then sharpens the knife on the buffing wheel which moves quite fast.
The speed can be controlled manually by pedaling faster or slower. The technique requires a lot of practice. One must learn it the hard way. But what is life without a little hardship.
It's an old method of sharpening blades in the Indian Subcontinent, Africa and even South America, apparently. The sound of the blade being sharpened is calming at times, and can be totally maddening the other times.
But the careful concentration and calm with which Kishan Yadav goes about his business was worth seeing. Looking at knifes being sharpened was never such a therapeutic experience before...