The reasons Why there is no flat burr manual grinder
Updated: Jan 17
As a coffee lover, we encounter many kinds of coffee grinders in our daily sip. They are distinguished by many special features like power source, burr types mainly, although there are more features like doser, burr material, body material, etc.
It's really a big family for coffee grinders.
But there is an odd phenomenon that you have met so many manual conical grinders, but you didn't have a chance to find a manual flat burr grinder.
Why there is no flat burr manual grinder? Let's check it out step by step
First, let's get to know about the burrs that are common in the coffee industry.
Conical Burr Principle:
This is a very useful burr that is widely used in the coffee industry. With lower cost and ideal outcome, low noise, the conical burr grinder win a big market and supporters.
It is integrated with an outer hollow round part with edges at the inner side and a solid conical part with the edges at the outer side. The round part is bigger and surrounds the conical part. The round part is stuck to the grinder body and won't move. The conical part is connected to a long shaft that can transmit the power from outside to the conical part for rotation. The gap between the round part and the conical part controls the fineness of the power outlet.
The working feature:
* Swallow beans by gravity.
* Outlet powder by gravity.
* Low speed
* Small diameter
* Outlet straight down
Are the words hard to understand? Let's check the picture below:
Flat Burr Principle:
Flat burr consists of 2 pieces of round flat discs in a similar shape that has sharp edges at one side. The sides with edges will be put face to face in the grinder. The gap between the two discs will decide the fineness of the coffee powder. One is fixed, one is driven by the power source and rotates to swallow beans by centrifugal force and crush the beans and threw them out from the gap.
The flat burr has many varieties like the normal flat burr, ghost burr, block burr, round burr. The only difference between them is the shape of the edges. Different edges can realize different characteristics of coffee powder.
Flat burrs are comparatively higher cost, higher noise. The debate over the flat burr and conical burr are still undergoing.
The working feature:
* Swallow beans by centrifugal force.
* Outlet powder by centrifugal force.
* High speed
* Big diameter
* Outlet from the gap at the sides
Let's check the picture I drew to understand it better:
So let's make an assumption that we will make a manual flat burr coffee grinder. Then we need to design it according to the principles as below:
1. The high rotating speed to create centrifugal force
The speed must be beyond 500r/min. So it's 166r/s at least. So need 166 rounds per minute!!
If a human can make this speed. He or She must be superhuman!!
Without this speed, gravity can pull beans down. But the beans can't enter the space between burrs smoothly. And the little amount beans inside the gap of burrs will be crushed slowly. And most importantly the fine powders generated will flow back to the beans instead of being thrown out.
So we need a transmission gearbox to transform low speed to such high speed.
This will cause the tool to have a big footprint. And the transmission gearbox must be high quality to bear the hand rotation. This will add extra high cost to the tool.
2. The big diameter of the flat burr
The flat burrs will have a bigger diameter but lower height compared to conical burrs. The diameter of flat burrs maybe 10 to 20mm bigger. So the diameter of the tool will be bigger with a little height reduced. The whole footprint is bigger.
3.Powder outlet from sides
The diameter is enlarged from above, but not enough. Due to the powder come from the sides, we need to design an extra big body with a bigger diameter to let the powder has space to come out. So just think about enlarging another 10-20mm diameter.