Middle bushing SB9 quick change gearbox

willy1 · Oct 5, 2015

I'm renovating my new 70 year old lathe and having difficulty driving out pin that locks center bushing in QCG so that I can properly align oil hole in bushing with casting hole by removing and reinstalling bushing. That misalignment is preventing me from removing and replacing felt oil wick. I am considering drilling thru the bushing by way of the hole originally used to drill hole in casting leading to oil galley where gits caps are located. Doing so will establish an oversize hole in the top of the bushing where the felt plug will go and leave a hole in the bottom of the bushing which I intend to drill, tap and plug to prevent oil from draining out. The bushing shows very little wear and the tolerances for spacing at the gears are within specification. Any thoughts on this proposed solution? Brand new to metal working and appreciate any comments.

kitno455 · Oct 6, 2015

drill the pin instead. it is soft.

allan

willy1 · Oct 6, 2015

kitno455 said:
drill the pin instead. it is soft.

allan

Thanks, Allan. Any idea where I might but a replacement?

tommy1010 · Oct 6, 2015

The pins can be a pain but with a little patience it will come out. You have access to both ends. They are tapered. When you replace the brass bushing you will have to ream the hole after the bushing is installed and set for gear clearance (.004) because the pin nicks the bushing to hold it exactly where you want it. A small tapered reamer is required for this. When you remove the old one you will see what I mean.

willy1 · Oct 6, 2015

tommy1010 said:
The pins can be a pain but with a little patience it will come out. You have access to both ends. They are tapered. When you replace the brass bushing you will have to ream the hole after the bushing is installed and set for gear clearance (.004) because the pin nicks the bushing to hold it exactly where you want it. A small tapered reamer is required for this. When you remove the old one you will see what I mean.

Thanks for the info about tapered pin. The book I got with lathe showed direction to remove pin but didn't mention taper. I guess McMaster's is the best place for reamer and new pin.

kitno455 · Oct 6, 2015

I think that pin is not tapered. Otherwise, it would crush the bearing. You should be able to drive it thru, with a good drift and small hammer.

allan

iwananew10K · Oct 6, 2015

I seem to remember that was a straight pin too.

tommy1010 · Oct 6, 2015

I have a number of boxes here for rebuild. All are a very small taper. 1/8 on the small end. When you install the pin after reaming the pin tightens in the cast iron and does not crush the brass. Reaming only removes a small amount of the brass bushing. Just enough to keep it in place. I am sure a straight pin will work the same way. You will have to drill through the existing holes to nick the brass. A little locktite and you are good to go. I do remember driving out a pin once and when it came out it had a curve to it. I guess somebody bent the pin to keep it in place. It may have came from the factory like that? Another idea for you to ponder is drill it out straight and use a split pin.

To the OP. If you drill through the hole used for the drilling the oil passage you will drill through the pin holding the bushing in place. Get the pin out first. Check and see if there is felt in that hole to begin with. That felt does not rub against the shaft in side the bushing. If it is there it is to slow down the oil so it goes to all the other lube points and not just run out at the point of least resistance.

willy1 · Oct 8, 2015

tommy1010 said:
I have a number of boxes here for rebuild. All are a very small taper. 1/8 on the small end. When you install the pin after reaming the pin tightens in the cast iron and does not crush the brass. Reaming only removes a small amount of the brass bushing. Just enough to keep it in place. I am sure a straight pin will work the same way. You will have to drill through the existing holes to nick the brass. A little locktite and you are good to go. I do remember driving out a pin once and when it came out it had a curve to it. I guess somebody bent the pin to keep it in place. It may have came from the factory like that? Another idea for you to ponder is drill it out straight and use a split pin.

To the OP. If you drill through the hole used for the drilling the oil passage you will drill through the pin holding the bushing in place. Get the pin out first. Check and see if there is felt in that hole to begin with. That felt does not rub against the shaft in side the bushing. If it is there it is to slow down the oil so it goes to all the other lube points and not just run out at the point of least resistance.

Thanks for all the help. Patience, and good guidance paid off. Hadn't really thought thru my idea of drilling thru the bearing. That REALLY would have been a mistake. Didn't notice I would drill thru the middle of the pin. Pin is out and on my way ,again, toward restoration.

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Middle bushing SB9 quick change gearbox

willy1

Plastic

kitno455

Titanium

willy1

Plastic

tommy1010

Stainless

willy1

Plastic

kitno455

Titanium

iwananew10K

Diamond

tommy1010

Stainless

willy1

Plastic

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