Rockwell Mill - bearing sound?

[agshooter]

I've noticed a sound when milling...but not always. It is a slight ticking/knocking sound. Today when drilling, I noticed no sound at all. It seems to only occur when milling under a load, medium to heavy cut.

Another thing I noticed today is when the collet is tight and I manually twist the draw bar I hear a the slight tick/knock. It's as if there is slight rotational play in the spindle.

Thoughts?

 

[Aukai]

Watch to see if the drawbar has enough play when the spindle is running to touch anything. If I'm not mistaken the drawbar is not really supported and can have some play when running, mine had a visual wobble, but the spindle ran true.

 

[machPete99]

I had that drawbar wobble on mine, it was due to the threads on the end being non-concentric. I made my own, using single pointed thread, and no more wobble. It is also a lot easier to tighten and loosen, can "palm" it.

The original spindle bearings in these mills are common deep groove ball bearings, with one side of the inner race ground down to provide some preload. Deep groove ball bearings are not really made for this duty, it was done as a cost saving measure, and typically does not have a long life.

The spindle step pulley also has a pair of deep groove bearings set up in a similar way.

I upgraded my spindle bearings to matched angular contact bearings for much better performance and long life, see:

Rockwell 21-100 Spindle Rebuild

Re-posting after server crash issue... I recently acquired one of these vertical mills, and will be rebuilding and refinishing it as time permits. Most of it is still in pieces, but I managed to just complete the spindle rebuild. I leveraged some ideas posted on the Yahoo Rockwell Milling...

www.hobby-machinist.com

 

[john.oliver35]

Another possibility is the splines between the drive pulley and the spindle. They have a little slop, and do wear and tend to knock. When doing any kind of cut where the tool load is variable (e.g. fly cutting) the spline will knock significantly as the load goes on and off the spline. When doing an operation like drilling where the load is constant, the spline surfaces always stay tightly engaged and there is no (or at least less) knock.

 

[agshooter]

Another possibility is the splines between the drive pulley and the spindle. They have a little slop, and do wear and tend to knock. When doing any kind of cut where the tool load is variable (e.g. fly cutting) the spline will knock significantly as the load goes on and off the spline. When doing an operation like drilling where the load is constant, the spline surfaces always stay tightly engaged and there is no (or at least less) knock.

That sounds like what I am experiencing. Is this something I need to address or is it is what it is?

 

[john.oliver35]

That sounds like what I am experiencing. Is this something I need to address or is it is what it is?

I wouldn't worry about it. I've run my 21-100 with some knocking for 5 years. My 'list' includes repairing it either by making a shaft and pully insert, or welding/repairing. I'm not sure that project will ever make it to the top of the list though.

 

[Oldvetteman]

I've noticed a sound when milling...but not always. It is a slight ticking/knocking sound. Today when drilling, I noticed no sound at all. It seems to only occur when milling under a load, medium to heavy cut.

Another thing I noticed today is when the collet is tight and I manually twist the draw bar I hear a the slight tick/knock. It's as if there is slight rotational play in the spindle.

Thoughts?

The manual for the Rockwell vertical mill shows an exploded view of the mill head. Near the top of the splined spindle there are three small holes, 120 degrees apart, into which three small round rubber bumpers are installed on the outer face of the splines. You can see the holes by removing the draw bar and looking down into the spindle with a flashlight. They are about 3/4" below the top of the spindle. You may have to remove some crud with a pick or Q-tip to see them. These bumpers appear to be intended to eliminate or reduce knocking between the pulley and the splined shaft as they rotate. They are shown as reference number 91 on the parts diagram and have the part number of TAB-175. One of my bumpers is missing and I sometimes get the sort of knocking you describe, depending on how my DIY draw bar is inserted and tightened. Missing or worn bumpers could be your problem.

 

[machPete99]

You can make new bumpers on a lathe using polyurethane rod stock, thats what I did for mine when I rebuilt the head.