What’s in Fritz’s head?

I was messing with the Fritz Werner mill last week drilling a small hole in some aluminum.  My mill seemed to struggle with the drilling and strained under the load.  I thought this was odd and investigated it a little more.  I quickly found that the bottom of the spindle was warm to the touch and, if pressed upward, was hard to turn by hand.  I figured something was amiss with the bearings in the head of the mill.

After a little bit of work I was able to remove the “spindle unit” from the machine.  I’m making up names for some of the parts because I’m not sure what to call them.  The “spindle unit” consists of the actual spindle, the bearings that support it, and a large block that encapsulates these parts.


Once I had the spindle unit out, I had to remove the threaded ring seen in the picture below.  There is a grooved key that is attached to the ring which engages a grooved  ring.  With the key removed, the threaded ring can be unscrewed and removed.


Next, the grooved ring, which is keyed to the spindle, and the upper thrust bearing can be removed.  FH3

Now the spindle can be removed out of the bottom of the block.  There’s also a large nut that screws onto the bottom of the block that can be removed.  As you can see, the lower part of the spindle has a conical plain bearing that has some discoloration and light scratching.  Luckily, the surface looks and feels much better in person than in the picture.  If it was torn up, I’d have had some serious issues to resolve.


If you peer down the hole the spindle goes through, you can see the lower thrust bearing.  There’s also a hole that reaches down to the bearing.


Looking at the block from the bottom, you can see the journal that the conical bearing rides against.  Notice there are some areas cut out of the journal wall that are filled with felt.  I believe that the journal section can be removed somehow because I see no other way to get to the lower thrust bearing.  I left it in place though after looking at the lower bearing and finding it to be in good shape like the upper one.


As you can tell, the spindle had previously been lubricated with grease.  The evidence of the hole leading down to the bottom thrust bearing and the felt told me that the spindle should be lubricated with oil instead.  I don’t know what idiot started using grease but it would have torn up the mill eventually since the grease couldn’t get to the lower thrust bearing or the conical bearing.  I believe that in operation the spindle was moving ever so slightly and contacting the journal.  Heat was then generated that closed the small gap in the conical bearing causing rubbing.

To remove the old grease, I wiped as much of it out as possible with a rag and then rinsed all the parts with a solvent.  I wiped all the parts down with oil and then reassembled the spindle unit.   I filled the spindle unit up with spindle oil and noticed that it was flowing out of the bottom pretty quickly. Despite that, I put it back in the machine and did the same drilling operation I’d done before.  The machine performed and sounded much better.


I figured the old oil seal was shot and removed just the spindle to get at the nut that held the seal.  I inspected the bearing by poking it.  It was inflexible and cracked pretty easily.  Luckily, the seal had the size molded into it and after measuring it to be sure of the size, I ordered a replacement.


The old seal was a pain to get out but the new one dropped right in.


I reinstalled the parts and topped the spindle unit off with oil again.  The new seal works much better and fixed the oil leak.

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