- Joined
- Mar 8, 2014
- Messages
- 41
Hi Everyone.
I will be grateful for any opinions/advice re fixing this problem, including whether my proposed solution is a good idea or not.
I have the Hare Forbes equivalent of the Grizzly G4003G lathe. I recently discovered that the quick-change gearbox is very tight (impossible to turn by hand) when connected to the leadscrew, even though the half-nuts are not closed on the leadscrew. Selection of the gear cone linkage to the leadscrew or the drive shaft is made by shifting a gear left or right. I would like to insert photographs of the inside of the gearbox to illustrate this but can't see any means of inserting a photos, so forget that. When the drive shaft is selected, the gearbox can be turned with ease. When the leadscrew is selected, the gearbox is very tight.
By removing the gearbox cover and investigating, I discovered that if the taper pin connecting the leadscrew to the gearbox leadscrew adapter is removed, the stiffness disappears and the gearbox turns easily. By gripping the immediately adjacent gear cone and turning, the difference in tightness can be assessed. If I replace the taper pin the tightness returns.
I surmise that the clever Chinese who assembled the machine drilled the hole for the taper pin in situ and by forcing the drill caused the axes of the adapter and leadscrew to be misaligned when the pin is in place, but allowing them to return their coaxial alignment when the pin is removed.
What do you think of my idea re the cause of this problem?
I don't believe the misalignment is severe - but it is sufficient to cause binding of the adapter in its bearing. My idea is to first test the misalignment by pressing on the adapter without the pin in place and see if it tightens the gearbox. If it does, I think I should place a wooden block firmly between the bed casting and the adapter to hopefully place them in an aligned position and use a taper reamer to re-align the hole. I doubt this will be a perfect solution but maybe it will remove the tightness. The only other solution I can think of is to remove the leadscrew and adapter and supporting them in an aligned position on my milling machine bed, drill another hole and ream it to correctly insert a new pin.
What do you think of this?
I will be grateful for any opinions/advice re fixing this problem, including whether my proposed solution is a good idea or not.
I have the Hare Forbes equivalent of the Grizzly G4003G lathe. I recently discovered that the quick-change gearbox is very tight (impossible to turn by hand) when connected to the leadscrew, even though the half-nuts are not closed on the leadscrew. Selection of the gear cone linkage to the leadscrew or the drive shaft is made by shifting a gear left or right. I would like to insert photographs of the inside of the gearbox to illustrate this but can't see any means of inserting a photos, so forget that. When the drive shaft is selected, the gearbox can be turned with ease. When the leadscrew is selected, the gearbox is very tight.
By removing the gearbox cover and investigating, I discovered that if the taper pin connecting the leadscrew to the gearbox leadscrew adapter is removed, the stiffness disappears and the gearbox turns easily. By gripping the immediately adjacent gear cone and turning, the difference in tightness can be assessed. If I replace the taper pin the tightness returns.
I surmise that the clever Chinese who assembled the machine drilled the hole for the taper pin in situ and by forcing the drill caused the axes of the adapter and leadscrew to be misaligned when the pin is in place, but allowing them to return their coaxial alignment when the pin is removed.
What do you think of my idea re the cause of this problem?
I don't believe the misalignment is severe - but it is sufficient to cause binding of the adapter in its bearing. My idea is to first test the misalignment by pressing on the adapter without the pin in place and see if it tightens the gearbox. If it does, I think I should place a wooden block firmly between the bed casting and the adapter to hopefully place them in an aligned position and use a taper reamer to re-align the hole. I doubt this will be a perfect solution but maybe it will remove the tightness. The only other solution I can think of is to remove the leadscrew and adapter and supporting them in an aligned position on my milling machine bed, drill another hole and ream it to correctly insert a new pin.
What do you think of this?