Inserting bits into collet

[djl]

Seems there are two trains of thought as to how far to insert a bit into the collet based on the "experts" on youtube.  Promoters of each method make valid points to support their point of view.  My question is which way is the correct way.  Collet is an ER-11 (1/4 inch)

Method 1 where the bit is not inserted all way into the collet - about 3mm from the Inside end of the collet.

Method 2 where the bit is inserted all the way in to the collet so that the flutes are about the distance as the diameter of the bit from the outside end of the collet

Pictures attached.

       Method 1                              Method 2

Doug

[eagle55]

I guess my opinion is that when you start making hard and fast absolutes my thought is that they are both wrong. (Or could both be right… sometimes. I think you have to ignore the “absolutes” and get a little bit of common sense involved. I think that the 3mm rule should be a minimum insertion rather than a maximum. Any less and you run the risk of not getting a uniform grip on the bit. I prefer to put the bit in as far as possible as long as the bit doesn’t touch the bottom of the spindle shaft hole in the middle. Touching anything other than the collet could cause runout issues. By the same token, if you have an absolute that you have to stop at 3mm from the end of the collet then for longer bits you run the risk of breaking the bit if it sticks out too far. I think the most reasonable approach is to put it as far in as possible without bottoming out or the cutting portion of the bit being in the collet. When you start having absolutes and toss out common sense, you are asking for problems. I tend to stay away from absolutes that don’t have sound reasoning…. Even when it comes from and “expert”. Or I should say especially when it comes from an “expert”. I think there are a lot of variables that should be considered.

[dadealeus]

Unless an "expert" can tell me why, I don't see any reason it shouldn't stick out the back of the collet (as long as there is adequate room to not touch anything else within the spindle).

As far as I can tell, it's literally the same as the front side of the collet aside from the taper - which is just used to exert inward pressure against the tool to hold it in place. Having the tool only partially inserted into the collet seems far worse than it occupying the entire length of the collet because of the uneven forces applied to the tool when the collet is tightened around it.

Additionally, the "slack" sticking out the rear of the collet should be no different than the slack sticking out the front. If the tool is bent, you're going to get some bad harmonics on either side.

Finally, too much stickout in the front seems a lot worse than more even stickout on either side of the collet. More stickout on either one side or the other makes resonance issues worse than if the collet were centered on the tool.

If you take a 3' long 2x4 and clamp it to your workbench so that 2' of the length are hanging free, then you stand on the end of it, you'll likely break it (depending on how much you weigh) because your entire body weight is applied like a lever to the end of the 2x4', far away from the fulcrum. If you take the same 3' length of 2x4' and place the middle of it on a 1' wide work bench, and clamp it across the bench so it can't bend, then stand with one foot on the end of each 1' foot stickout, your weight is applied evenly to two levers of half the length and it's going to be a lot harder to break either end.

In the case of a spinning tool, the mass of the tool is exerted outwards via inertia and isn't much different than the force you exert on the board via gravity except for the spin. Either the entire stickout's mass is working against its own structural integrity on one side (with full leverage at the fulcrum where it meets the collet), or the mass is divided across two levers that are much shorter (and, therefore, exert less force on the fulcrum) on either side of the collet.

So, like I said, unless someone can explain the exact physics to me regarding why this is a bad idea, I'll continue to do it and recommend reducing stickout as much as possible (as long as the flutes are clear of the collet).

[djl]

eagle55, dadealeus

Thank you for the replies.  Confirms what I have been doing all along.  I too do not understand the idea of not inserting the bit all the way through the collet.  Perhaps somebody from Axiom will chime in and explain why the bit should be inserted all the way through the collet rather than leave the end of the bit  approximately 3mm inside the collet.
Doug

[aluomala]

I use Amana bits pretty much exclusively (I use Kyocera scoring bits for fine v-carving), and there is a "stick out" mark on the bit (see photo). I always insert it so that the minimal amount of the bit is showing, and don't have the stick-out marker extend beyond the collet. I have heard that having the flutes inside the collet can damage the bit, so I avoid that, but having too much bit out is worse, in my estimation. I suppose I should have chosen a better photo/bit for my example, but this image showed the marker the best from the ones I found online. 

[dadealeus]

Dec 7, 2023 21:37:18 GMT -5 aluomala said:

I use Amana bits pretty much exclusively (I use Kyocera scoring bits for fine v-carving), and there is a "stick out" mark on the bit (see photo). I always insert it so that the minimal amount of the bit is showing, and don't have the stick-out marker extend beyond the collet. I have heard that having the flutes inside the collet can damage the bit, so I avoid that, but having too much bit out is worse, in my estimation. I suppose I should have chosen a better photo/bit for my example, but this image showed the marker the best from the ones I found online. 

That 1/2" shank can fit in ER-20, ER-25, ER-32, and ER-40 collets. The difference in collet length (height) between the ER-20 and the ER-40 is over half an inch.

If inserted into an ER-20, that cutter is going to stick out the rear of the collet by nearly 3/8ths of an inch by design.

If inserted into an ER-40, it's going to end about 3/8ths of an inch inside the collet sleeve.

I'm guessing that if this was important enough to really matter, it would be standard practice for tool manufacturers to standardize tool shaft lengths so that they would either always end within the sleeve, or outside of it.

In short, I wouldn't be concerned about choking up on the tool if you're concerned with excessive stickout.

For example, I have a 6" long, 1/4" diameter, 2-flute up-cut that I periodically use for some very deep cuts, but I don't hesitate to choke up as much as I can for whatever cut I need to make and I've never had any issues (again, ensuring there is no contact being made between the rear of the tool and my spindle).


Amana Tool Schematic:

www.amanatool.com/53813-carbide-tipped-finger-grip-trapezoidal-1-3-4-inch-dia-x-13-16-x-1-2-shank.html

Collet Size Details:

littlemachineshop.com/info/er_collet_sizes.php