Atlas Mill Spindle Pulley Bushing

[JPMacG]

I was really happy with how my mill is running. I have spent about a year working on it and thought I finally had all the bugs out. Then, while running it with the back gear engaged, the motor belt started to slip. So I tightened the belt and continued working on my project. A few minutes later one of the pulleys on the counter shaft started to slip. I was mildly annoyed and started to tighten it when I thought.... wait a minute.... whats going on here...

The bull gear and pulley/gear assembly were locked together even though the pin was disengaged. They had seized to the spindle shaft. I was able to drive out the spindle with a mallet and some wood.

The bushing (Oillite?) looks terrible. It is scored in many places and has an area where the surface is very rough. The spindle shaft has a corresponding rough area but I think I can polish it out. Is the bushing a standard size? Can I simply press it out, purchase a new one and press it in? Has anyone been through this before on an Atlas mill?

 

[Hudspeth]

I had a similar problem with my 4 gang pully on the spindle of my atlas lathe last week. I was having problems with the back drive being noisey. I took it apart and pulled the spindle only to find part of one bearing and whats left of the other. The pulley was severely damaged on the bore IE out of round. My fix was to hone it until roundness reapeard and went to the local hardware store and bought a bronze bearing with smaller id and larger od than the spindle and pully. I honed the inside to fit the spindle and honed the pulley to fit the bushing about 1.5 to 2 thou interfearnce fit and pressed it in to the pulley. I reassembled the lathe and the back gearing is soooo quiet now. Very happy didn't have to hunt down a replacement pulley. I felt helpless with no functional lathe......

 

[pollardd]

At least on my 10" Lathe, one thing I learned by chance a while back is that there is a grub screw on the spindle gang pulley from memory in the Vee of the second smallest pulley.
The sole purpose of this screw is to oil the spindle. It doesn't tighten down on anything. I just remove the screw once in a while and give it a squirt of oil, then wind it back down until the top of the screw is below the surface.
I have a feeling this hole is documented on the oiling chart somewhere.

I've never had the spindle / Back gears off to check their condition. I have been leaving my Babit bearings well enough alone

Good luck replacing your bearing. Please post your solution as well.

Regards
David

 

[wa5cab]

Probably the main reason for problems with the spindle pulley and bushings found on almost all Atlas lathes and all mills is that too many people follow "if all else fails, read the manual". And by that time it's usually too late. The lubrication instructions are readily available (every copy of the MOLO plus scattered elsewhere), and most of them caution against over-tightening the oil plug and turning it into a set screw. There is a Sticky above on the subject and has been for several years. It would have been better had Atlas counter bored the tapped hole in the spindle pulleys and used a socket head screw as a plug. That would have removed one of the two reasons for failure..

 

[JPMacG]

Thanks everyone. This was a replacement part that I purchased on eBay. The original pulley/gear assembly that came with the mill had the dogs torn up so that the gear would not stay engaged. I noticed that the replacement's bearing looked questionable when I installed it. Anyway, if I am successful with the bearing replacement I will be sure to keep it oiled and not tighten the oil plug.

Some of the oil hole set screws on my lathe have a flange at their head that prevents them from being screwed down below the surface. But the mill does not. A previous owner replaced the mill plugs with Allen set screws. I like this because it is easier to insert them, but it is also easy to forget their purpose and tighten them.

I'll post photos as I progress.

 

[wa5cab]

Not that it matters so long as the slide moving over it doesn't hit it, but all of the original oil hole screws in the carriage or knee were #8-32 x 1/8" headless cup-point slotted set screws.

 

[JPMacG]

I removed the bushings from the pulley/gear assembly last night. They came out easily using a properly sized round rod and a few light taps from a brass hammer.

For anyone who might care, the bushings measure 1.000 OD x 0.875 ID. The lengths are 1.31 and 0.41. The longer one has a groove on its ID for oil flow and the shorter one has a notch that prevents it from partially covering the oil fill hole that goes through the pulley. The oil fill hole in the pulley connects to the empty volume between the two bushings.

They appear to be solid bronze - not sintered. I wonder if it would be OK to replace them with sintered (Oilite) bushings. That would avoid the need to broach the oil flow grove. What do you think?

 

[wa5cab]

I would say no to replacing the notched and longer bushing with sintered bronze un-notched. In the first place, had that been a good idea, Atlas would have done it to begin with. The reason that it wouldn't be a good idea is that (not necessarily in order of importance) (1) the long bushing would never have oil standing over it, (2) where the spindle stops must be assumed to be random so less than 50% of the time there would be oil standing against the short bushing, (3) unlike with the oil cups over the bronze spindle bearings on the 101.07301, there is very little volume between the screw plug and the bushing.

 

[JPMacG]

Thanks Robert. That seems like sound advice.

Here is a photo of the notch. The notch is about 0.012 deep, 0.1 wide, and 0.4 long. I could mount the part in the 3-jaw chuck of my lathe, lock the chuck rotation, and cut the notch by moving the carriage by hand to the left. I could do it in several passes, using the cross slide to control the depth. For a cutter I might use the blade of a parting tool.

But I would be left with burrs. How would I remove them? If I file them off I will risk damaging the critical internal diameter and surface finish of the bearing.

 

[fixit]

run a hone through it from the other end. should take the burrs off.

fixit