1. The first question is how a bit have to be inserted into a collet relatively to the collet lips' ends (inside the collet). Are these two following cases justified or some among them is wrong or better? 2. The next case is when I have two collet which have different length of the support lips. I wonder is the first collet with 12.5 mm length of the support lips rigid enough to grip a bit reliably? Or do I have to pick the second one with more extended support lips? 3. When a bit abuts onto the collet lips (inside collet) and simaltatiosly the beginning of the bit's flute touches outer ends of the collet's lips, is it normal or maybe necessary to move the bit a litle bit out of the collet? 4. And the conclusive question. How to determine and more curiously how to push the right torque onto a collet nut to secure a collet with a bit on a spindle correctly? Is it bad if it will be over tighten, since I afraid that a bit can slide inside its collet if I apply insufficient torque with wrenches?
N1 is right, you dont want too little of the bit gripped by the collet You also want the least amount of stickout that will get the job done. so if the bit has 20mm of flute length, but the cut is 25mm deep, stick out 26mm is correct. (provided there is space for the collet nut to get that close to the work of course.) but you also don't want too little of the shank being gripped by the collet, you at least want the hole filled as in N1
That is, if a bit has long enough shank length to move the bit beyond/futher the ends of the collet support lips, is it all right ?
To get the best cutting results: 1. Cutting length of the bit should be only slightly greater than the thickness of the material being cut. 2. Bit should extend out of the collet no farther than absolutely necessary. Top of machined cutting edge should be within a couple millimeters of the collet. 3. Collet should have a full grip on the shank of the bit (and only on the shank of the bit). 4. Bit should not be allowed to bottom out (top out) in the spindle shaft cavity. If it hits, pull it back out a few millimeters. If this violates item 2 above, get a shorter bit. There is nothing wrong with the bit extending beyond the collet grip a reasonable amount. I generally have 5 to 10 millimeters to spare with no issues.
