This is also a common reason for tool breakage when it occurs Breakage often

This is also a common reason for tool breakage when

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This is also a common reason for tool breakage when it occurs. Breakage often results in permanent damage to the collet due to intense pressure exerted often either "Burring" or mushrooming the mouth of the collet. Heat is the biggest enemy of the tool, and the first place the heat goes from the tool is into the collet. It is also important to note that collets are made of spring steel that can, and will over a period of time lose its elasticity and harden, making it increasingly tougher to tighten adequately. As this hardening takes place, the steel does not fatigue evenly and often causes the collet to grip tighter on one side than the other, creating runout in the tool. It is important to understand that if they are overrun enough this over tightening will eventually damage the internal spindle taper resulting in costly repairs. Because it takes place over a period of time, it is very hard to notice. A safe recommendation for collet life is in the 400 -600 run time hours. This is about 3 months in a two-shift operation of normal run times. If collets are not changed, they will eventually become brittle enough to crack or break in half potentially causing permanent spindle damage that could have been avoided. Just like changing the oil in your car, it is good preventative maintenance that should be done regularly. Cleaning the collets each and every time the tools are changed is just as important as replacement. Collets are in a brutally dirty environment and are expected to perform a very accurate task while undergoing some real extremes of heat and dirt. As material is routed, whether it be wood, plastic, aluminum or man-made board, the chips carry with them many resins that migrate up the slits in the collet and deposit themselves onto the inside of the collet ears, usually nearest the mouth of the collet. This miniscule migration is often the cause for tool breakage when seen in the actual shank area of the tool instead of down by the cutting edge. The resin acts like pressure points gripping the tool tighter at the mouth of the collet. These pressure points often distort the grip on the tool creating runout, this resin heats up as the tool does and actually ends up depositing itself onto the shank of the tool almost gluing the tool into the collet leaving brown marks at the mouth of the collet contact on the shank. These brown marks are sure sign of collet neglect. To prevent this problem the resin must be removed from all surfaces that it is prone to buildup using a non-abrasive brass tube brush for the inside of the collet and a mild solvent and rag for the external surfaces of the collet and inside spindle taper. It is important to point out that blowing out the collets does not get rid of the resin, nor does soaking them overnight in thinner.
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  • Fall '19
  • Tools
  • Milling cutter, High speed steel, Cutting, Collet, Downcut Spiral

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