Today I bought packets of 2 Columbian coffee beans thinking it was the ground one and when I got home I was very disappointed as it was coffee beans and I do not have a coffee grinding machine. I tried crushing the coffee beans with the end of the rolling pin on a bowl, took ages to crush half of a bag, however it was not fine enough that when I tried brewing it, it tasted so weak. I do not really want to go back to the shop and have the one of the un-opened coffee bags replaced as the petrol would cost more than the coffee price. But anyway, I found a great solution to grinding coffee beans, I use a blender! It only took a minute to grind the whole bag (227g) of coffee beans and got the perfect grain. So if you do not have a coffee grinding machine, try a blender, it does the job well!
After grinding the coffee beans using a blender, the result is the same as the ones you get on a packet of ground coffee.