The internal grinder is another name for the more widely known stainless steel grinder. They are great little machines and can get a job done very quickly, but for the home barista the advantages of using an internal grinder can easily outweigh the drawbacks.
Although, having one does not mean you have to buy the most expensive grinder that fits your budget. The most common type of internal grinder in the market is made out of plastic and has a lot of moving parts which makes it prone to breaking and/or clogging. If you decide to go with a plastic internal grinder then you can also consider investing in a separator, which will allow you to clean your grinder and keep it working at top notch speed.
With stainless steel, you are going to get what you pay for. Although, stainless steel grinders are generally more expensive than other types of grinder on the market, they are worth every penny.
Another advantage of using a stainless steel grinder is that they are easy to maintain. All you need to do is to wipe down the inside with a paper towel after grinding, and do not forget to rinse the grinder out and wash the grinder grub (which can get stuck inside the grinder).
And yes, this is just the beginning. As long as you maintain your grinder well, you will be able to get a top class espresso at home.
On the downside, these types of grinder can be somewhat noisy. You can also expect to spend a lot of time cleaning and maintaining your grinder. If you are the type of person who enjoys spending a good amount of time grinding your own coffee beans, then you might want to reconsider getting a grinder.
There is one final word of advice that I would like to leave you with. When purchasing an internal grinder make sure you take the time to read some reviews on the product you are considering. If you know someone who has used the grinder or even someone who has used a more expensive model, please pass along their comments and opinions.
Here is a final note. When buying an internal grinder, make sure you check with your local (state) liquor laws as some grinder models do require a permit to operate.