How often should we replace CNC tool holders and collets?
Question (CNC Forum)
We've been using the same tool holders (HSK 63) for two years now. I've seen recommendations to replace these on a yearly basis. That would be quite expensive for us, as we have over 30 of them. I do chuck them into a lathe every 3 months or so and clean the rust off of them. Is it really necessary to replace them? They still seem to perform fine.
As for collets, I only replace them when edge quality becomes unacceptable. As with the tool holders, is it necessary to replace them on a set schedule, or do most of you go by feeling?
Predicting the span life of a tool holder is extremely difficult. Different types of tool holders react differently to cutting forces. so frequent inspection is important.It is best practice for shops to clean and inspect tool holders and spindles after every job. Tool holders should be completely disassembled and cleaned. A contamination-free tool holder and machine tool spindle interface ensures tool holders properly seat at full taper contact and are pulled into the spindle taper at maximum force. With holders held and positioned accurately, a machine’s full power and tolerance capabilities can then effectively and safely transfer to the cutting tools, while runout and vibration are reduced for superior part surface finish quality.
Collets should be replaced every 2 to 3 months if being used 8 hours a day. When inspecting your collet, metallic damage, such as bell mouthing or burrs, should be checked with every tool change. If damage is visible, the collet should be discarded and replaced. But sometimes collets can be damaged without any visible signs. The most common problem is metal fatigue. An easy way to see if there is metal fatigue is to insert the tool shank into the back of the collet and then try it in the front side. If the tightness is not the same both ways, then the collet is fatigued and should be discarded. One major cause of collet metal fatigue is from overtightening. A tool holder tightening stand and torque wrench should always be used.
Collets are manufactured from softer metal than tool-holders and feature special slots and cutouts allow-ing them to “collapse” and “spring” to tightly grip the cutting tool. As a result, they will wear out faster than the holders will.
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