Runout mystery

I am having bizarre runout issues. I have attached a link to the video. Basically the Bt30 tool holder has almost 0 runout then I release the tool holder and turn the spindle or tool holder half way around and put it back in. Then I get about 10um of runout. Repeat and their runout is gone. Change tool holder (different brand) same result. I can’t even beggin to guess what is causing this. I have cleaned all collets, tool holders , the taper and even the belt. I have tried 3 different brands of tool holder with same results. The spindle is new <20 hours on it. The whole mill is only a few months old. Anyone have any ideas?
No I can’t just mark all the tool holders and use them on the 0 runout side because sometimes both sides have the 10um runout.

@Dr_Harold_Jones while I wasn’t able to watch your video or see what’s going on, the thumbnail shows that you are using ER tool holders? If that is the case, the collet itself is probably where the runout is coming from. What I would recommend doing is taking the tool and collet out of the holder and measure the inside of the tool holder where the ER would normally reference against.

Here is a great video by John Saunders did talking about runout and showing you how to “dial in” an ER tool holder.

Where are you measuring to?
I would start at the inside taper of the spindle and work my way out. Then the collet taper in the holder. Use a gauge pin in the collet. Be sure to check vertical alignment first. If that’s bad, everything else is crap.
Also if you’re looking for 10ths accuracy, you really need 100 thou scale.
Some do and some don’t, but i like a very thin coat of oil in mating surfaces, helps things seat. Not the mill itself though.

+1 on what Bruce Keller said, tho I would think the shank of a carbide end mill is pretty accurate. So out of curiosity I tried a few things, straight off my tool rack, no Saunders ‘tapping things true’:
empty BT3- spindle bore <= 1 micron
tool shank in Maritool SK10 holder: ~ 1-2 microns
tool in Maritool ER-16 with Tecknics DNA ‘dead nuts accurate’ collet: <= 1 micron
tool in regular ER-16 collet: ~8-9 microns!

The issue here is that I a measuring the tool runout as 1 micron and then simply pressing the drawbar release, rotating the tool holder 180 and putting the tool holder back in the spindle. Then the runout is 10 microns. If I repeat the above on the same tool holder or pick another tool holder it goes back to 1 micron.
Runout mystery

Sorry, been out the loop.
Inspect all holder surfaces for witnesses marks, ie not symmetric. Check the pull stud, tight and seated completely. Ah, use a mirror and flashlight and check the pull mechanism in the spindle ( can’t remember proper term) and lube it. Think antisieze is recommended. Maybe the collet is sprung?

Done all that. This is a machine that was installed in march and the spindle was replaced in June. I am refreshing the video link. I know it’s long but it really shows how strange this is. I have almost 0 runout and then when I remove the tool holder rotate it 180 degrees and reinsert it I have loads of runout. Do the same again (with the same tool holder or a different one and it goes back to 0 +/- . It has to be something in the spindle that only affects one side of a cylindrical surface across multiple brands of tool holders and pull studs. I might send in a ticket. My brain just can’t comprehend how a symmetrical circular mount can be centred in one arrangement and wobble in another.

It’s long but it’s very strange.

Ok, first thing I noticed was that your indicator lever should be around 15 deg to the surface. That will give you most accurate reading. Kinda looks like it was pushing on it funny.

I tried a old 3/8" edge finder body in a ER20 collet, snugged it in my hand with a crescent wrench. Had about 0.0025" runout. Went 180 deg and got about the same using a 10ths indicator.

Loosened it, put it in the tightening fixture and torqued it to 45 ft lbs. Runout dropped to less than 0.001".

Then I used the shank of a carbide tool. About 0.0007 runout. Not bad for just throwing it in there. Nothing close to what you are getting.

Maritool sells a torque wrench and adapters for torqueing collet nuts and pull studs. Had to modify one to torque the ER20-M nut but can use it on the ER20-A nut also.

I torque everything so I know I’m doing the same thing every time. Very small drill bits and endmills etc under 1/8" I tend to do by hand because it’s easy to over torque the nut and collet. But everything else I torque. Also measure up closer to the collet, tool quality isn’t what it used to be.

Make sure the indicator is sitting at the correct angle so you are getting a true runout and try torqueing. A thin coat of oil on the collet taper and nut threads, not the tool itself. But remember, oil can increase torque up to around 10%.
See what that does for you.
Nice drill chuck by the way!