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ER40 Collet runout *Anyone else want to throw an indicator against a wall

Speedie

Stainless
Joined
Feb 24, 2009
Location
Midwestern MN/Wi USA
ER40, bearing nut, small drills that are running out .002 on the tip. Spindle .0002 run out, collet taper .0002 like the spindle. Using a nut with a bearing and a precision collet...or so I think. When I tighten the nut the collet runs out .006 inside when tested. The nut bearing has some slop in it. I am thinking this is where the runout is coming from. I tried multiple tools, spinning the collet reduces the runout which brings me back to the nut bearing. Anyone seeing the same issue?
 
Tony did a video on this very topic just this month... at the very least it's good entertainment :)

 
You could even have a situation where the nut thread to inside taper is off, ditto external thread to taper error on the tool holder. But that seems unlikely...

You must have other collets the right size, have you tried swapping them? Or tried a different nut?
 
Make sure the collet and nut are perfectly clean, and that the shank of the drill is going all the way through the collet.

If it's still running out I'd swap the collet and nut and see if it's still out. Is this a holder you've indicated as good before? (with a nut, collet, and tool in it)
 
For all of those in between sizes when circular interpolating? I would set them aside for fussy projects.


I'll just open the door and let myself out.
 
.006 runout of the collet with nothing in it? you mentioned .002 at the tip of the drill and .006 at the collet inside. I wouldn't trust it to run true with nothing in it.

The long taper side of the collet inside the holder is doing more for running true than the nut side.


How about clamped on the shank of the drill, runout of the shank itself (or gage pin) ?

"small" drill in er40 collet: could you use er16 or er25 or something?

What brand collet is this?
 
ER collets don't get concentric by the nut's 60° taper, they get concentric by the 8° taper. The nut is a source of error in ER collets.

Other collet types with flat groove surfaces, like SK type, don't have the same problem.

In any case, if you have pinpointed the source of runout to the collet/nut, there's no way to fix it without changing the weak link.
 
Junk collet nuts. Something old tony overlooked in his video.
Usually bearing nuts are decent, did you buy this tool holder from Amazon or Alibaba?

There are other types of tool holders and collet systems that generally have less runout than ER collets. If you want to avoid collet nuts entirely, there are some tool holders that use narrow pull-back collets, and since they have narrower taper angles than ER, they grip better too, and have a back stop so putting in a replacement drill doesn't need a touch off gauge length measurement.

ER collets usually fall in the range of 5 to 10 microns of runout. Bad ones more, good ones less. SK, DS, VC, and other types of collets are more like 1-3 microns.
 








 
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