Advantages of the ER Collet System

by Bernard Martin

ER, IT’S IN THE DETAILS

The ER collet system has several advantages when using today's CNC computerized milling machines. The most significant advantage is flexibility to hold any type of round shank tool.

​An ER collet can be used in drilling, reaming, and tapping as well as milling applications just by exchanging the collet. Its accuracy also provides greater tool life than older style collet systems like TG or DA.

Another advantage is the flexibility of the collet for clamping a wide range of tool shanks with a small number of collets. ER 16 through ER 40 provide a collapse range of ~.039" flexibility for clamping cutting tools. This is a benefit for you because you will not have to carry as many collets in inventory for the different jobs you need to do each day.

The ER collet also provides more holding power by using two principles.

1. The first is the 8 degrees (16 degrees included) back taper which is based on the engineering principle that 7.5 degrees is a mechanical lock for tapers. You notice that steep taper toolholders (CAT & BT) have the same taper for the same reason.
2. Secondly, the ER collet has a larger front nose taper than many other collets. It's 30 degrees and provides more surface area for the nut to contact the collet. This translates into higher clamping pressure against the shank of the tool. Most manufacturers can also provide a bearing nut, which enables the clamping power to increase by 100%. Coated Nuts can increase this clamping power even more.
   

In addition to mechanical differences, the ER collet is also user friendly. It is a self-extracting collet, which eliminates the need for collet squeezers to extract the collet by any other means than screwing the nut off. This enables the operator to spend time running the machine, not extracting collets.
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These basic principles allow the ER collet system to be the most widely accepted collet system in the world for holding round shank cutting tools.

• Flexibility - Drill, tap and ream with same collet holder.
• Accuracy - all collets are 100% examined for accuracy.
• Longer Tool Life - Less runout, greater tool life for carbide tools.
• Wide Clamping Range ~.030"
• Less Inventory of Collets - Larger clamping
• range reduces inventory.
• Easy to Use - Self-extracting collet from holder .
• Can effectively eliminate the need to dedicated tap holders.

ER style collet chucks should be used for the bulk of your needs. They are the most dependable, with the least runout, both in and out of the cut, are readily available (so the prices continue to drop) and will give you the best tool life out of the lot of them.
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Advantages of the ER Collet System