Best way to hold an endmill

How to hold an endmill?


Holding an endmill properly is very important in achieving the best results. When holding an endmill you want to have a solid and concentric cutter. If the holder is not solid the cutter will deflect once it touches the work piece. When the cutter is able to move around in the holder this can cause vibration. If the cutter does not run concentric the endmill can produce a bigger cutting diameter than the endmill size. It can also cause chipping or excessive wear on one side of the cutter. 

Collet holder



A collet is a round tapered collapsible holder. They come in many different sizes usually up to 1" depending on the series. This is the most popular and widely used type of holder. Collet holders come in many different series for example the ER series. This series has many different sizes.  For example there is ER8, ER11, ER16, ER25, ER32 and ER40. As the numbers get bigger so do the holding diameter of the collet.  There are 3 parts to the collet holder,

 1. The body (shown in the picture above on the left.)  This is the part the goes into the spindle. They come in many different styles for your spindle, R8, Cat40, Cat50, BT40, HSK, ect,

2. The nut forces the collect against the taper closing the collet. Most collects will snap into the nut. To remove the collect from the nut you must push the collet to the side, do not pull it straight out. 

3. The collet holds the cutter by collapsing around the diameter. Collets are made in standard inch and metric sizes and can be collapsed to fit any size in between. 

Pros: 
Can hold many different sizes of cutters. 
Can be very accurate, less than 0.0002" run-out

Cons:
Not as rigid as a solid holder. 
Limited to 1" diameter shanks or smaller



Solid Holder

A solid endmill holder can be a very rigid and accurate way to hold an endmill. This is a very simple design where an endmill shank slides inside a very accurate hole and using a set screw will lock the endmill in place. Most HSS and indexable cutters have a flat spot on the shank, this is where the set screw should sit. A solid holder will only hold one size, and are made in standard inch and metric sizes. 

Pros:
Very rigid
Can be very accurate , less than .0002" run-out
Come in very long lengths with reduced vibration. 

Cons: 
Can only hold one size per holder. 



Drill chuck


Drill chucks should never be used to hold an endmill. Hence the name DRILL chuck , only for drills. 

Why? Drill chucks were never meant to have side force on them, only down force. Even if you only want to plunge with them they will not be very rigid or concentric enough to hold an endmill. Using a drill chuck to hold an endmill can result in broken cutters and scraped parts.