Bit Slip on Chinese Spindle

[analogman]

During a very long operation (+1 hour), my 1/2" bit started to slip (down), ruining the job. Any suggestions on how I can prevent this from happening in the future? The collet was on very tight.

[ger21]

Make sure both the bit and collet are very clean. If they are, then it wasn't tight enough.

[LazyMan]

Same thing happened to me once, but the bit came very loose and stopped cutting properly. Almost caused some serious damage. Ever since, I make sure the collet is super clean and tight when using larger bits.

[giveinfo]

I use Chinese spindle, it works for 5-6 hours without problems (8mm end mill).

Just clean it an tight it.

[analogman]

Thanks guys - yeah there was some dust in there. Cleaned it spotless - that did the trick.