ER 40 Collet Chuck Runout

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weejax

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I just got an ER 40 collet chuck for my mill. My spindle has a little less than .0001 runout. My cheap R8 collets with a rod in them have .0001 to .0003 runout. The ER 40 collet chuck had almost .001 runout on the inside taper. I contacted the company and they sent me a new one. They advertise .0001 TIR or less. The new one I got I am measuring .0007 on inside taper. When I put a collet in I get .001 runout on a ground pin. Am I being overly demanding to be concerned about this? Its a higher end taiwanese chuck and not an ebay special. One other question, (that I cant seem to find any answer to on the internet): is it bad for the spindle bearings to change ER collets with the chuck still in the spindle? Id think the spindle, just doing its normal job, sees alot of lateral forces. thanks for any advice.
 
It should meet specification, I have several, Iscar and Shar's and they all measure ~0.0001". Better ER collets are usually rated at 0.0002" TIR. I use them to align my center finder and they TIR using a carbide end mill shank is usually 0.0002" TIR. It is important to snap the collet into the collet nut first and then attaching it to the arbor, otherwise the collet will not seat properly.
 
I guess I will send this one back. again. its from glacern, which had good reviews. maybe they got a bad batch. i would think there was something going on with it mating up correctly in my spindle but my R8 collets do just fine. I just ordered a 1340gt and will be following your instructions on the VFD. THanks again!
 
weejax said:
I guess I will send this one back. again. its from glacern, which had good reviews. maybe they got a bad batch. i would think there was something going on with it mating up correctly in my spindle but my R8 collets do just fine. I just ordered a 1340gt and will be following your instructions on the VFD. THanks again!
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One thing to check before you send it back, is the state of the collets themselves.

Often with import collets, you'll find grinding debris and chips left in the slots from manufacture.

Import collets do need to be scrupulously cleaned before using for the first time (and of course, cleaned of any chips any time you use them, then onwards).

Worth a check, anyway. :)
 
SouthernChap said:
One thing to check before you send it back, is the state of the collets themselves.

Often with import collets, you'll find grinding debris and chips left in the slots from manufacture.

Import collets do need to be scrupulously cleaned before using for the first time (and of course, cleaned of any chips any time you use them, then onwards).

Worth a check, anyway. :)
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That is a fair point, however @weejax did say that:

weejax said:
The new one I got I am measuring .0007 on inside taper.
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Given that fact, I would suggest it is not the collets per-se, though they may have a higher TIR, but a combination of the TIR of the taper in combination with the collets. If the Taper of the collet chuck has a higher than stated TIR, then the retailer has a duty to replace for one with the stated TIR.

All that said, I wonder if that error could be a result of the R8 taper having an effect on TIR?

@weejax have you tried sweeping the inside taper of the collet chuck with a lever dial held in the spindle of the mill, whilst holding the Collect chuck vertically and carefully in a vice or clamp arrangement on the mill bed? It would answer the question to a certain extent. You may need to know the TIR of your spindle to do that, but it is something to consider.

Also worth checking the R8 taper of the collet chuck too.
 
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Also take a look at your drawbar. My original one was rather crappy, could see the runout at the top and had vibration when running, might also put some uneven stress on the R8 collet. I remade my own, carefully single point threaded, and with a precise centering washer at the top. Made a world of difference.
 
When evaluating runout, there are several considerations. The first is that there is no such thing as absolute zero runout. What there is , is runout small enough to be insignificant regarding the ability to measure and/or the task at hand.

The second consideration is that runout is composed of two elements, radial and angular. Radial runout consists of a parallel offset of of the measured axis relative to the spindle axis. That is, at every point along the measured axis, the runout is equal in both distance and direction from the spindle axis. In the diagram below, that is depicted as condition B. Angular runout occurs when the measured axis is tilted relative to the spindle axis but intersects the spindle axis at some point, shown in condition C. In the general case, both exist and the measured axis is tilted but never intersects the spindle axis, shown in condition D.\

Runout Cases.JPG

Measuring runout at a single point will not give a true indication of the conditions. Runout is usually specified as as radial runout at two distances. and it usually measures better at distances close to the chuck, collet, etc. It is possible that the two measured values could be equal but in opposite directions, giving a false indication the angular runout is zero. One has to note the spindle rotation to be able to discern that condition.

The third consideration is that measured TIR is a composite of multiple elements. In the example of a mill, there is the spindle socket, the collet, chuck, the collet, and the test bar. In order to properly evaluate the actual runout, is is necessary to parse out the contributions of each.
 
Well damn, that is a well of information in a single post!
 
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