[Bennyhill]

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I have a serious run out on my mill, my head is tortured with it all week and would appreciate any guidance, I am new to this so excuse the incorrect description of items I try to describe.
Have purchased a less than a year old mill AMAT25LV, similar to G0704/BL20/TM25 with brushless motor and belt drive.
The mill came with MT3 chuck and full set of collets, I have purchased a plunger dial indicator and spot drills and edge finder.


With the quill, table and Z axis locked i am reading 0.03mm to the inside of the spindle, the reading is repeatable and does not move around, when I place in the MT3 chuck it depends where i put it in the spindle, reading the inside of the chuck there is one one point i have identified where i can get the lowest reading of 0.005mm but if i remove the chuck from this point, turn it around and put it back in again it reads as high as 0.07mm in places.


Ok, a work around would be to keep the chuck in the spindle at the sweet spot.... but not so fast unfortunately when i put a spot drill or edge finder in the collet it depends what way the collet is turned, it has a sweet spot of 0.015mm but around 0.05 everywhere else, the measurement is taken as the drill leaves the collet, further down it is much worse, I have tried different collects and drills to be the same.


I have checked that the collets and chuck is clean and free from debris, i have removed the spindle, removed the top bearing, refitted and tightened down the pre load on the bearing, with no difference.


The more measurement i take the more confused i get, is it obvious i have been caught ?..... what would you do to go forward, replace the bearings 7008 and 7005, do you agree that could be the issue, is there anything else you can think of that i am doing wrong or can check, am i correct that I should be seeing 0.01mm or better inside the spindle.


Many thank for taking your time to read this.

[handlewanker]

Hi, get real.....forget about the run out, put a cutter in the chuck and make some parts.......you'll never ever improve a cheap manual mill that runs on dovetails and is made down to a price......oh yeah, throw away your dial indicator as it's not telling you anything you can fix without spending more than the machine cost for a rework.

It's as simple as this, if the spindle, collet or cutter runs out .02mm....then the cutter diam is .04mm diam bigger and you'll only find that out when you take a cut after you touch the edge of the revolving cutter against the part you want to cut.

Under a CNC mode, you will be relying blindly on the stated diam of the cutter to arrive at the part dimension when it makes a cut, taking deflection in the quill, shoddy chuck and cheap collets into consideration.

Buying expensive high end tooling for a cheap manual mill is like sewing patches onto rags with gold thread.

With regards to the chuck runout........you have two reference points that can throw the cutter out of true rotation..... the outside M3 taper on the chuck and the inside colllet locating taper...........if you have onlý .03mm runout in the spindle that's as good as it's gonna get unless you do a spindle taper regrind while it's running in it's own bearings.

Mounting the chuck in the spindle means you now have a taper seating for the collet inside the chuck that can be running out of true to the spindle taper.....only cure is to regrind the internal collet seating taper while it's in the spindle taper.........this will give you the maximum accuracy that the spindle has which will be .03mm......learn to live with that.........if you get really nit picking strip the spindle out and regrind the M3 taper.

I won't even mention the fact that the collets have a taper and a bore that can also be out of true to each other.

You have 3 mating interfaces that must be true to each other about a common rotation axis, and they are all made by different people at different times without any relative testing to one another for accuracy of rotation......don't ask me how I found that out.
Ian..