[bit pusher]

I'd like to tighten up my z-axis ball nut mount. I dont want to remove the whole assembly from the column, just the large housing for the motor and spindle assembly, essentially everything forward of the three large screws (at 3,6, and 9 o'clock) that hold it in place. I've never had the head off the machine before and wanted to ask for some advice before I try anything.

Long ago I had a conversation with Tommy about doing something like this and he mentioned:
1. setup some 2x4 pieces of wood on the mill's table to keep the spindle's nose from touching or supporting the weight of the head.
2. gently lower the head onto the wooden blocks on the table so that it is resting there.
3. unscrew the bolts from the three large screws in the head
4. slowly move the Y-axis forward and separate the head from the saddle column
5. perform maintenance as needed

To re-attach:
1. align the head's saddle (on the column) with the head which is still resting on wooden blocks
2. move the y-axis backwards until they're in contact again
3. tighten 3,6, 9 o'clock screws
4. re-tram the head to the table

For those who've done this, am I missing anything, or are there any tips or advice you could offer?

thanks in advance

[arizonavideo]

I did the same. It slides around easy. A strap is a really good idea to keep it from falling over. You hold down kit works well to give you mounting points.

[bit pusher]

Thanks for the reply. I talked to Paul at Charter-Oak, he suggested similar. His advice was to get eye-bolts threaded to match the t-slot nuts and rope it down.
I made a wooden saddle of sorts to hold the head assembly out of some poplar scraps I had laying around. I cut a pocket about 75mm deep and 106mm in diameter for the spindle housing to prevent it from touching anything.

The reason I'm doing this is to tighten up the z-axis assembly as much as possible. I've got a vibration that happens when the spindle is spinning at 6500rpm and I retract the head for a tool change. There is no vibration when the head is stationary with the spindle running, and there is no vibration when the spindle is stopped while the head retracts. Hope this works

[bit pusher]

Got the head off cleanly. The wooden "platform" I made is holding it pretty snug. It separated from the slide on the column with no stress and seemingly no effort.
I can now get an unobstructed view of the ball screw. It vibrates and rattles a bit when I retract the head. I suspect the ball screw may be tilting a wee bit to one side or another due to a mis-aligned ball nut mount.

I'm still waiting on my 12mm hex key to get here. I'm going to try loosening the cap head screw a little bit and adjusting the ballscrew assembly until it minimizes wobble when moving the slide up and down.

Is there any danger of the slide falling unsupported if I remove that cap head screw completely to put some blue loctite on it? Should the gibbs hold it in place?

[bit pusher]

I resolved three problems with my mill in the past 2 days:

1. Binding in the Z Axis while lowering the head: After I had the head off I lowered the slide as much as possible. I ran my finger up and down the z-axis dove tails until I found some burs and uneven edges. I smoothened them out gently with a flat file. This was not isolated, there were lots of edges that were not completely level. This took about 30 mins to gently smoothen out and wipe clean. The head is now absolutely smooth in its descent with no hints of stuttering or binding even at 175 in/min.

2. Visible vibration on the Z-axis ball screw when raising or lowering the head: This root caused to the z-axis ball screw mount not being quite tight. Paul at Charter_Oak gave me some great advice here, suggesting that I raise the slide as high as possible, lock the gibbs, remove and clean the 12mm cap-screw, apply blue loctite, center the ballscrew and tighten the assembly. I tightened it down monkey tight. The result was very smooth travel up and down with no visible wobble or audible vibration.

3. Loud audible vibration when retracting or lowering head while the spindle was spinning at high speed: This was very tricky to root cause. I initially suspected that my belt drive was not quite centered and introducing some unevenness into the spindle. I did loosen up the screws and followed Dave's instructions to quiet down the belt drive. I tapped it back and forth, left and right gently while spinning it at 2000 rpm, it did make a minor difference in overall noise but did not resolve my issue with vibration while moving. I found the real problem when I was remounting the motor and noticed that the single screw on the left side of the plate to which the motor mounts had become loose. Note that this screw is completely covered by the motor's base plate and will unscrew slowly over time as you repeatedly change the belt from one pulley to another. I cleaned that screw and added blue loctite. I tightened it as much as I could while still retaining the ability to swap the belt. This should be regarded as a sub-optimal fix as unmounting the motor to get access is a serious pain. I will probably punch a 1/4" hole in the motor's mounting plate so I can tighten that screw if the vibration recurs in the future. Doing this dropped the audible vibration by about 90% while running at 6500rpm and moving at 175in/min. I'm pretty happy with it.

This little exercise over the past few evenings resolved just about all the major annoyances I've had with the mill. I've re-trammed the head and buttoned everything back up. The whole procedure was a great learning experience. Many thanks to Paul and Dave for their advice.

In case anyone is interested, this is the wooden fixture I used to hold the head while I fixed up the Z-axis ball nut mount and dove tails.