Need Help!- Issues with my mill

[Hack]

I have spent the past couple of years converting my round column mill / drill to cnc. Did all the good things, lapped the ways, geckos, ballscrews, etc. X and y went great, but z .... The machine had sat for 2 years and the quill had rusted to the point where it seized up. I disassembled it completely, removed the rust from the quill with fine sand paper, honed the inside of the head stock casting and reassembled everything. I finished the z axis and am now cutting under full 3 axis cnc control. But......

This thing cuts horribly. Vibrates like crazy when I cut. Never did this before when manual milling.

For example a 2 or 4 flute 1/2" endmill (HSS or Carbide) at 2000 rpm .030 DOC and 8 to 10 inches a minute chatters very badly. To the point that I need to wear ear plugs it is so loud. Faster or slower feed and rpms do not seem to help. Even light .010 DOC and 25% stepover does not improve it. It seems worse climb milling then conventionally cutting. This is a R8 spindle with a 2 hp motor and I am only cutting 6061 aluminum. I should be able to plow through this stuff. So what did I do?

I checked the spindle and made sure the thing was tight. Snugged it up a bit more, but it's tight. I can't feel any play. Did i bend something removing the spindle? I could put and indicator on it and check for runout, how much should I see typically? Other things to look for? It does not feel as though it is in the table or base, but the head itself and then radiates throughout.

Driving me crazy. I spend alot of time and money on this to be disappointed.

Thanks for the help.

Dan

[arizonavideo]

I have a real RF-30 and the quill fits quite tight. If you sanded it and honed the bore it will have more play. Try disconnecting the Z stepper and locking the Z and see it it cuts the same. If the ring is gone then it is the quill.

If not the top spindle bearing may have got rusty.

[Torsten]

Good advice from arizonavideo this would be the first thing to try.
It you find the locked quill will run much better, then you can investigate further.
Bearings and preload.
slope in the column guide, should run with spindle not to far extended.
Backlash sould be minimised as far as possible.
On my Jet JMD-18 converted to full 3 axes computer controll I can take easy 0.06 inch depth of cut in mild steel without much vibrations.
Good Luck

[Hack]

Well after a month I finally took a look at this machine. Tightened the z and the sound in nearly gone. About all I notice now is a bit of sheet metal vibration but 90% is gone when tightened. I can live with it now.

What are my options with a fix however? I really think this is just something that I will live with but if I do decide to make any repairs, where would I want to start. Would I need to replace the head casting and / or quill at this point?

FYI, My tests were at .060 DOC in 6061 aluminum 10 IPM 1/2" wide cut. I know that is not necessarily pushing this mill, but it is acceptable for hobby use like me.

Thanks for the help.

Dan

[RICHARD ZASTROW]

Dan, If the headstock is a true cylindrical bore after honing, you could grind the spindle to a true undersize cylinder. Plate the spindle oversize and grind to the correct fit.

This is a common "fix".

Dick Z