Milling Rite

[Dave Bonzo]

I can't get a photo of it, but: the issue is within the bevel gear at the top of the elevator screw...and I'm kind of stuck, now.

I removed the elevator shaft collar with the intention of pulling the shaft, but it can't be removed: not only is the shaft riding in a bearing inside a web inside the knee, but the bearing doesn't move with the shaft...so, I'm effectively trying to pull a Big Thing through a Small Thing, and that just doesn't work. But wait...there's less: the taper pin that's hanging out also cannot pass through that bearing, so the elevator shaft is effectively double-locked into place.



That being said: with the elevator shaft collar removed I can better feel what's happening up there...and at a certain point in the shaft's rotation, the bevel gear on the elevator screw wants to physically push the spur gear away. This movement is telling me that there's some kind of debris or deformation happening up there on the top surface of the bevel, where I can't see anything. I think my next step is to try and get eyes on the top side of the bevel gear, somehow. I might have room to sneak a tiny mirror up there.

This being said: even if I can get a look at what's happening, I don't know how to fix it. I have no idea how any of this was put together, because it seems to be about six kinds of impossible.

Oh, and the taper pin? Yeah, it's not actually falling out. It's just too long, as best I can tell; I tapped a wire against the opposite side hole and didn't get it in very far...so the pin is either in most of the way, or something else that's totally unknown is taking place.

 

[pontiac428]

Well, this started off on the wrong foot.

Pictured: Uhh...what?

I'm gonna hazard a guess and say that 1) someone's been in here before, and 2) they lost a screw... literally. So that might explain why something else is going on inside the knee. Not sure what I can do to fix it, if anything, but I might as well have a look.

You are probably right, but there is a chance that other-sizing the bolt in the beefiest part of the boss is a method of indexing the mating parts. I've seen similar with line bored matched parts that don't have a staggered pattern. But, like I said, you're probably right, especially if that wasn't the case on the Y leadscrew retainer.

 

[pontiac428]

This being said: even if I can get a look at what's happening, I don't know how to fix it. I have no idea how any of this was put together, because it seems to be about six kinds of impossible.

Does the drive assy and screw come out with the knee? As in, can you unbolt the base end of the jack screw and pull the whole knee off and get it on a bench at this point?

 

[Dave Bonzo]

Does the drive assy and screw come out with the knee? As in, can you unbolt the base end of the jack screw and pull the whole knee off and get it on a bench at this point?

Yeah, I think that's what has to happen.

I got the elevator shaft collar removed - the stop collar that holds it in place was semi-seized, so that was fun - and I can see a bit inside the knee...and there's a bit of a window in the rear, between the ways. Still can't see anything inside, though; the internal webbing in the knee blocks everything.

That being said, I'm thinking that I basically have to swing the entire head out of the way, loosen the elevator screw nut, and then somehow lift the knee off the base. Problem is, I don't have anything that'll accomplish that. A cherry picker or a chain fall would make immense amounts of sense, but I don't have either...and I don't have a place to store one.

 

[pontiac428]

Can you support the knee, remove the gib strip, and pull it away without sliding it up all the way to completely clear the ways?

 

[Dave Bonzo]

Can you support the knee, remove the gib strip, and pull it away without sliding it up all the way to completely clear the ways?

I can't, unfortunately; removing the gib won't give me enough clearance...and I think I still have to get the elevator screw out of the way.

 

[Ischgl99]

You should be able to rent an engine hoist, then you won’t have to worry about storing it. That would probably be the safest way to remove the knee.

I can’t find my borescope, so can’t see far enough inside the knee to see if the gear is small enough to pull out with the vertical feed shaft, the drawing in the manual looks like it might, if the taper pin was not in the way. I’m thinking the window in the back of the knee is how that taper pin got installed, so I think your only option is to remove the knee.