- Joined
- Dec 18, 2019
- Messages
- 6,397
I had just finished my boring bar holder this past week and wanted to try it out. Grabbed a chunk of 1045 steel and drilled a 1/2 hole in it to get clearance for my 3/8" boring bar. Bored out about an addition 0.1", not all at once, but in 0.010" bites. Bar was cutting well and making 1/2" tight curls.
Then I heard a loud noise and some following squeaking and the bar stopped feeding inward. Thought I damaged the bar, the insert or the half nut. The spindle was still turning. I was not at the bottom of the bore, but about 0.150" from the bottom when this happened. Stopped the lathe and started trying to figure out what had happened. Moved the carbide boring bar towards the center of the hole and extracted the bar. It was fine. Poked around some more and eventually found the B/C gears had seized on the shaft. They would not move. Ordinarily, the bushing freewheels on the shaft.
Pulled out the B/C shaft by loosening the nut and tried moving the gears on the shaft. Very stuck. Eventually removed the 20T metal gear and examined the 80T gear. It had turned in the shaft about 180*. Pressed the gear off. Well nuts, I'll need a new one. It appears the bushing seized on the shaft? I've got it soaking in a little bit of Kroil right now. Maybe I can free it up. Or make another one. The bushing, shaft and gear altogether is only $22.06. It's the time - it will be a week and a half before I get the parts. With the shaft assembly in a vise tapped the bushing keyway to try to rotate it on the shaft. It's not moving.
Glad I had a plastic gear for this. It was the mechanical fuse for the system, the weak link. My best guess is the lubrication between the bushing and the shaft was insufficient.
Well, that puts a damper on things. Need to check that this is the only damage. Maybe there is something else. Suppose more disassembly of the gear train is required. Anyone have ideas on what else to check?
Then I heard a loud noise and some following squeaking and the bar stopped feeding inward. Thought I damaged the bar, the insert or the half nut. The spindle was still turning. I was not at the bottom of the bore, but about 0.150" from the bottom when this happened. Stopped the lathe and started trying to figure out what had happened. Moved the carbide boring bar towards the center of the hole and extracted the bar. It was fine. Poked around some more and eventually found the B/C gears had seized on the shaft. They would not move. Ordinarily, the bushing freewheels on the shaft.
Pulled out the B/C shaft by loosening the nut and tried moving the gears on the shaft. Very stuck. Eventually removed the 20T metal gear and examined the 80T gear. It had turned in the shaft about 180*. Pressed the gear off. Well nuts, I'll need a new one. It appears the bushing seized on the shaft? I've got it soaking in a little bit of Kroil right now. Maybe I can free it up. Or make another one. The bushing, shaft and gear altogether is only $22.06. It's the time - it will be a week and a half before I get the parts. With the shaft assembly in a vise tapped the bushing keyway to try to rotate it on the shaft. It's not moving.
Glad I had a plastic gear for this. It was the mechanical fuse for the system, the weak link. My best guess is the lubrication between the bushing and the shaft was insufficient.
Well, that puts a damper on things. Need to check that this is the only damage. Maybe there is something else. Suppose more disassembly of the gear train is required. Anyone have ideas on what else to check?