# Atlas Mill arbor runout



## JPMacG (Oct 23, 2019)

The arbor on my MFC has a bit of runout - I think about .02".  This causes the cutter to cut in a cyclic manner.  I still get good machining results, but the cyclic noise is concerning me.  In addition to the cyclic cutter noise, the back gears clatter as they are loaded and unloaded every cutter cycle.

The arbor is very old, probably original equipment with the mill, and probably has been abused over the years.  Mymachhineshop.net has new arbors for sale, but I don't want to replace the old arbor unless it is truly bad.

How much arbor runout is typical?


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## matthewsx (Oct 23, 2019)

Hi, I can't speak to typical runout on your machine but twenty thousandths sounds like a lot. There are a number of good threads on here about measuring runout so make sure you're measuring it correctly before assuming anything.

That said, $169.99 doesn't sound like a whole lot to get your machine back into spec. You might just give them a call and see what they recommend for your specific machine since they seem pretty knowledgeable.

Cheers,

John


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## RobertB (Oct 23, 2019)

matthewsx said:


> Hi, I can't speak to typical runout on your machine but twenty thousandths sounds like a lot. There are a number of good threads on here about measuring runout so make sure you're measuring it correctly before assuming anything.



Yeah, also not familiar with the MFC, but to me .002" is a bit of runout and .02" is shake the machine across the room runout.


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## GrayTech (Oct 23, 2019)

I concur, .02" or .5mm is a lot of runout for a mill. That is likely to wear cutters really fast in one spot and also any gears in the power train. 
When you say arbour I'm assuming we're talking about a horizontal mill?
Is the arbour bent or maybe the mounting taper is messed up?


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## jcp (Oct 23, 2019)

I seem to remember about .003 runout on ours (at the middle of the arbor). 
A new operator at our shop had a crash with our large horizontal mill. A couple of hours with the press and a dial indicator had the mandrel back to usable condition.


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## markba633csi (Oct 24, 2019)

I agree with jcp, it should be possible to straighten if you have a press and some patience
You might also be able to find one on Ebay for a reasonable price
M


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## wa5cab (Oct 24, 2019)

First thing to do is to determine whether the problem is caused by the arbor, the taper in the spindle nose or the spindle bearings.


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## JPMacG (Oct 25, 2019)

Thanks everyone.  I measured again, this time on the cutter itself.  The total indicated runout on the cutter teeth is .003.  This is with the cutter mounted at the approximate center of the arbor.  The .02 I mentioned before was on the OD of a (low quality) spacer.  

So now I am confused as to why I get the cyclic cutting.  It may just be that I need to increase the feed rate or take deeper cuts.  Or there may be something else going on?


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## RobertB (Oct 25, 2019)

First, measure the runout on the arbor itself, at several different points along its shaft.

Are you getting this cyclical issue with all of your cutters?


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## jcp (Oct 25, 2019)

Our horizontal mill made cyclic sounds, particularly when taking a 'light' cut. When it was running at max depth of cut and feed it was pretty steady.......  still noticeable, but not distressing......nature of the beast I suppose.


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## JPMacG (Oct 27, 2019)

I had some time today to make better measurements.  The total indicator runout on my bare arbor (without the cutter and spacers) is under .002.  I checked both ends and the middle - and they are roughly the same.  Also, to answer RobertB's question, yes, the cyclic cutting is the same for all  my cutters.

I am concluding that, as JCP said, it is the nature of the beast.  I need to take deeper cuts, or increase the feed rate, or both.


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