ER collets are offered in many different types and offered in many different sizes. The problem is that if you’re not careful with your purchase, you may end up with a lot of machining issues. This is a classic example where you do get what you payed for….
To start, ER collets do offer a lot of range, most will offer a gripping range of a full 1 mm, but the TIR of your cutting tool may shock you. If you are using an ER collet to grip and drill a hole, then bore the hole, most likely you are ok. If you plan on running a spot, tap drill, and tap, the TIR issue can give you a lot of problems, and broke taps.
The problem is simple to solve with 2 suggestions.
- Always purchase ER collets to size, meaning run a 1/8 ER with a 1/8 shank or 4 mm ER with a 4 mm shank, and avoid using that “gripping range”. This is just good common sense.
- When you purchase the ER collets, ask for Precision or Super-Precision variety. They are available, and these offer TIR down as low as .0002 of an inch and that just may be what you need for that small hole, precision work…
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