05-07-2012, 11:05 AM
(This post was last modified: 05-07-2012, 11:17 AM by henryarnold.)
I got so anxious to post my pictures I didn't post much of an explanation about why I have been doing this job. I did explain that I had a leak but not from where or my suspicions of why. This message should have been the first in this thread but it's easier to write now after a few discoveries and while I wait for the paint to dry. I hope this is helpful to those contemplating this repair.
My leak was from the quill end of the mill. Oil was coming out from where the lower bearing is. I verified this by removing the threaded plate with three indents. This is not good because the oil washes the grease out of the tapered bearings. With this being a home use mill, I could have ignored it but being picky about tool maintenance, I wanted to fix it. I'm also up for an adventure of fixing something I've never fixed before.
The RF-45 and RF-40 Chinese and Taiwanese Mills have a gear box where six speeds are available. The head is much like a simplistic automobile transmission. The speed selectors move gears that slide on the internal shafts using brass shoes to move them. There are 3 major seals on the input and output of the gearbox and two smaller seals on the speed selector shafts. There are four shafts that run vertically inside the head/gearbox. There is one shaft for the motor input with one seal, one shaft for the spindle output with two seals, and two intermediate shafts where the speed selection occurs which are internal only and have no seals. The motor input shaft is at the top of the head and is not likely to leak much. Oil would not have anywhere to go from this seal. It mostly protects the motor. The output shaft which drives the spindle through a sliding spline has two oil seals and is buried inside the head. These seals are redundant. I think that there are two in case a little oil gets past one seal. When these seals leak, the oil gets into the quill /spindle assembly. There are two directions for the oil to take when it gets past these seals, past the quill, or through the quill bearings. Most of my leaking oil was coming through the quill bearings.
As I disassembled my mill I discovered two interesting things which may explain why I had a leak. First, the seals around the shaft that drives the spindle were installed upside down with the lips pointing away from the oil filled head. Second the round plate the seals were installed inside of is attached to the cast iron head with three screws and a gasket. My gasket showed signs of oil getting past it which circumvents the seals. I fairly certain that upside down seals and a leaking gasket are the root cause of my leak.
Unfortunately getting to these two seals requires taking the whole head apart. Once the head is apart and the seals are being replaced, it made sense to me to also replace the bearings. That said, I have to admit that none of my bearings looked bad. I could have taken the mill apart and just replaced the seals and probably been good to go. Doing so would have simplified the job because I would not have had to pull any bearings. If your mill is clean inside, you may consider just replacing the two quill drive shaft seals. My mill had a brown muck inside which confirmed that I needed to replace the bearings.
I thought about this repair for over a year before starting. I knew it would be a big job. Thanks to Ed for giving me the kick-start I needed by starting his mill repair first. Be sure to follow his thread which has photos of parts of the repair I failed to photograph.
My leak was from the quill end of the mill. Oil was coming out from where the lower bearing is. I verified this by removing the threaded plate with three indents. This is not good because the oil washes the grease out of the tapered bearings. With this being a home use mill, I could have ignored it but being picky about tool maintenance, I wanted to fix it. I'm also up for an adventure of fixing something I've never fixed before.
The RF-45 and RF-40 Chinese and Taiwanese Mills have a gear box where six speeds are available. The head is much like a simplistic automobile transmission. The speed selectors move gears that slide on the internal shafts using brass shoes to move them. There are 3 major seals on the input and output of the gearbox and two smaller seals on the speed selector shafts. There are four shafts that run vertically inside the head/gearbox. There is one shaft for the motor input with one seal, one shaft for the spindle output with two seals, and two intermediate shafts where the speed selection occurs which are internal only and have no seals. The motor input shaft is at the top of the head and is not likely to leak much. Oil would not have anywhere to go from this seal. It mostly protects the motor. The output shaft which drives the spindle through a sliding spline has two oil seals and is buried inside the head. These seals are redundant. I think that there are two in case a little oil gets past one seal. When these seals leak, the oil gets into the quill /spindle assembly. There are two directions for the oil to take when it gets past these seals, past the quill, or through the quill bearings. Most of my leaking oil was coming through the quill bearings.
As I disassembled my mill I discovered two interesting things which may explain why I had a leak. First, the seals around the shaft that drives the spindle were installed upside down with the lips pointing away from the oil filled head. Second the round plate the seals were installed inside of is attached to the cast iron head with three screws and a gasket. My gasket showed signs of oil getting past it which circumvents the seals. I fairly certain that upside down seals and a leaking gasket are the root cause of my leak.
Unfortunately getting to these two seals requires taking the whole head apart. Once the head is apart and the seals are being replaced, it made sense to me to also replace the bearings. That said, I have to admit that none of my bearings looked bad. I could have taken the mill apart and just replaced the seals and probably been good to go. Doing so would have simplified the job because I would not have had to pull any bearings. If your mill is clean inside, you may consider just replacing the two quill drive shaft seals. My mill had a brown muck inside which confirmed that I needed to replace the bearings.
I thought about this repair for over a year before starting. I knew it would be a big job. Thanks to Ed for giving me the kick-start I needed by starting his mill repair first. Be sure to follow his thread which has photos of parts of the repair I failed to photograph.
henryarnold, proud to be a member of MetalworkingFun Forum since Apr 2012.