Escape the Grind... how to dial in your grind.

“Dialing in the grind” is the process by which you change the size of the grind to get the extraction of the coffee perfect. You are adjusting the size of the particles in the ground coffee bean by adjusting the width between the grinding wheels or burrs in the grinder.
There a a few things to consider before we even touch the adjustment on your grinder.
There is a very strong train of thought that suggests you should spend as much money on your grinder as your coffee machine. While that is a little bit hard to do with such quality machines available for in home, the sentiment is clear.
Search the net and you will find plenty of examples of coffee experts being unable to pick the difference between an espresso produced on a commercial machine vs an in home machine. The common thread is the use of a high quality and well maintained grinder feeding both machines.
Firstly why is the quality of the grind important- the grind size and relative grind size distribution are key to consistent extraction. If the grinder produces grinds of all different sizes (on a constant setting) when the pressurised water passes through the group head the water will extract the volatiles and oils inconsistently. Hence you will get an inconsistent espresso.
Secondly the grind size in itself effects extraction. If the coffee particle size is large when the water passes through it in the group head it flows easily - like water though gravel. The high flow does not allow sufficient time of extraction producing a weak and sour coffee. Oppositely if the coffee particles are too small the water cannot get through and the extraction is burnt and bitter.
The goldilocks grind setting is somewhere that allows the coffee to flow through consistently over around 30 seconds producing the best the bean has got to offer.
An example of dialling may be something like this.
You have a new bag of freshly roasted beans that you have never tried before. You put them into your grinder and using your standard settings fill the portafilter. You tamp as normal and begin extraction. The espresso flows freely and produces 36g of espresso in 20 seconds. This is an under extracted shot and likely to be slightly bitter. Not a great result for an expensive coffee that promised so much. Throw that shot away. Adjust your grinder to make the grind size smaller. Each grinders adjustments are different and as you approach the end of the grinding burrs life it requires bigger moves. On a normal grinder you may require an adjustment of two clicks down. On a stepless grinder one turn.
Repeat the shot. Your extraction is slower. The grind particles are smaller and the water finds it more difficult to get through it. The result is 36g of espresso in 27 seconds.
One more adjustment down and you are there!!
Congratulations- you made a big step to get in touch with your inner barista.