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| How do I fix my milling machine runout? |
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| raynerd:
I`ve noticed the last couple of holes I`ve drilled have been quite oversize, when I made a concious effort to watch the chuck it was clear that it was not turning true, it had a clear hight and low point. I got out my nice DTI and measured the runout on the flat of the chuck which was measuring 0.27mm!!! I put in a stub drill and was measuring the same off there! So I removed the chuck and put the DTI on the outside of the mill spindle to find a runout of no more than 0.03mm. I then put the DTI on the inside of the spindle and actually the runout was less, just vibrating within one of the 0.01mm divisions. I cleaned the inside of the morse taper and put the chuck back in, inserted a stub drill and measure a runout on the drill flat of 0.17mm. An improvement but still terrible! So I`m confused. Clearly the spindle is running true and after cleaning the spindle bore/morse taper I expect the chuck to be seating correctly. Could something have happened to my chuck? - seems unlikely. Anyone any suggestions as to what could have happened or how to improve this before I continue to use my mill? :( |
| doubleboost:
What make of chuck is it Some of the cheep ones are total crap If the spindle is running true it can only be the chuck |
| Blade:
The chuck on one of my drill presses had quite a bit of runout, I put a carbide bit in the jaws of the chuck and put the whole thing in the lathe and rebored the taper on the chuck. You have to be careful not to remove too much so that the taper wont go too far into the chuck. and bottom out before seating. |
| jiihoo:
Hi, Let's see if we could do some troubleshooting here: According to your measurements the spindle mouth runs true but the drill chuck doesn't. Thus either the drill chuck or arbor is faulty or something inside the spindle morse taper is preventing the arbor from seating correctly. Do you have collets or morse taper endmills or drills or even a morse taper dead centre from your lathe that you could test with (basically anything that you could mount directly to the spindle)? If they test true, then it is definitely your chuck and/or arbor. When you cleaned up the morse taper, did you explicitly check for burrs both inside the spindle and in the drill chuck arbor? Do you remember if the arbor has slipped in the spindle lately? One thing you could test: if you can get the drill chuck and arbor separated, you could measure the runout on the arbor and thus prove that the arbor is good ==> then you know for sure it is "just" the chuck. Can you go visit a friend with the chuck/arbor or borrow a similar one off a friend for measurements? Have you ever measured your chuck's runout before or was this the first time (i.e. do you know that it has ever been "perfect" or could it have been slightly off from the beginning and just gotten gradually worse over time)? If it is just the drill chuck, then there should be no reason to stop using the mill :thumbup: Cheers, Jari |
| raynerd:
Well I`ve read your advice, ignorantly I thought it was immediately a problem with the mill and didn`t consider the chuck so I`ve now removed the drill chuck and measured run-out with my er32 collet chuck - it has now gone down to 0.09mm. This still seems high to me - is this acceptable? Move it back up to the outside of the spindle and it is about 0.03mm. The outside of the er32 collet chuck is about 0.05mm but I guess this is irrelevant as the centre of the chuck doesn`t have to be necessarly concentric with the outside but still thought I`d measure. Hummm... does 0.09mm seem about right (about 0.0035") ? Chris |
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