Thread: AL 320G Lead screw DOR gears

Having just spent ages cleaning the gear head up, I turned my attention to the gears that control the lead screw DOR, listed in parts manual as Left Trestle. Apart from the usual contamination etc, the first thing I discovered was there were no oiling points for three of the shaft bearings. There are four oil point for two gears and two bearings, but I guess the others just run dry untill the grind themselves out.

There is no way to get oil to the points by drill holes etc (that's possibly why they didn't bother) and the only solution I could come up with, is when I reassemble the unit to seal the back cover (and any other leaky points) drill a hole through the top of the casting and add a small bath of oil for the lower gear to run in and hope it can splash a bit of oil around the box and hopefully into the bearings.

There is also a small thrust race that I assume should have grease in it, but it too was dry as a *******

So whats the opinions and is the oil bath worth a try?

Hi
What are these blanked off holes for?
Are you sure they arent oil galleries so you oil 2+ bearings from one oiler?

Stuart

Hi Stuart,
No, the holes closest to the shaft have pointed screws that hopefully hold the bearings in place, and the other four are thresed to take screws to secure the back-plate to the casting. It's that plate I'm thinking about sealing to create a small well of oil for the bottom gear to run in.

Out of interest, there was not one screw in the entire unit that had been tightened up.
George

Hi George,

I'd be surprised* if they were for holding the bearings in, are the bearing or bushes?


Only two problems I see with your plan.
1. what are the seals on the leadscrew bearing like?(are there any?)
As the output side of the gearbox appears to be covered, if the oil didnt leak out to fast you could make a tray that catches the oil and just tip it in the top at the start of each day.
2. whats the seal on the selector like?(though I'm guessing that much higher?)


Stuart


*though there is a lot I havent seen yet with luck someone who has one will be along shortly.

Stuart, you are correct, the ones in question are bushes, and of a grey iron type material, though I'm not sure exactly what it is. The leaks from some areas would be of slight annoyance, but nothing that's going to gush out, cant be wiped up and replaced.
George

Originally Posted by georgedgerton

So whats the opinions and is the oil bath worth a try?

The oil bath is worth a try but as the lower gear will be turning very slowly, I doubt it will splash oil at all.

Also the oil level will be limited by leakage from the bottom shaft and will be very low as a result.

Looks like a pretty crappy bit of design engineering on this lathe.

Rob

Originally Posted by georgedgerton

So whats the opinions and is the oil bath worth a try?

The oil bath is worth a try but as the lower gear will be turning very slowly, I doubt it will splash oil at all.

Also the oil level will be limited by leakage from the bottom shaft and will be very low as a result.

Looks like a pretty crappy bit of design engineering on this lathe. I've never been a fan of the AL320G - I've looked at it very closely.

Rather than use oil, you may be better off putting a grease nipple in the face plate and pumping the whole gearbox full of grease.

I think this would do the job nicely and as the shafts are turning slowly there would be no heat build up.

Rob

I'm not sure grease will do much for the bushes if its just sitting in the box??

There must be a way to get oil where it needs to be, even if you have to add some extra oil lines. (brake line could be a good place to start). You may even need to drill a gallery in the shaft?
Would need more pictures.

Stuart

Hi George
I think Rob is right, the gears will be going to slow for good splash oiling. For my little machine .15mm/rev freed equates to about a 16-1 reduction from the spindle speed. Not very fast at all even at top spindle speed.
Did you pull the gearbox to bits or have you just taken it off at this stage? If you pull it to bits some pics of the bearings etc would go a long way to helping us see what may be done to get some oil in there.
Looking at the pics on the h&f site its not really a gearbox is it? Just the forward/reverse for the feed/lead screws.
A few oil holes and ball oilers in the right spots would be my best suggestion, even if the oil just trickles down onto the gears, as long as you oil it regularly it will be fine.

Hi, just by chance I had the left trestle on my AL320 off today for the purpose of replacing the ball oilers which have never worked, there are four of them on this item, two in the middle just drop oil straight onto the gears and one each end which feed down a hole to the main shaft bushes, I believe Stuart is correct, the two blanked off holes with the grub screws have been drilled through to meet the vertical oil line behind it thus feeding both shafts from one oiler, the bushes have a hole in the side so need to be lined up correctly,
the grub screws are just to block oil leakage, I'm replacing the ball oilers with angled drivefit grease nipples to be used with oil as out of about a dozen ball oilers at least six were jamed tight since new
Leroy

Leroy, thought you may have a point with holes being drilled through, so I tried pumping oil under a bit of pressure through to see where it went. As you can see the oil is starting to leak from the top shaft, but there were no further signs of it finding it's way to the lower bushes. Eventuall oil was flooding from the top, but nowhere else.oil.jpg

Thinking about it,the others are right, the lower gear probably won't splash any oil around, so that looks like a "fail"

George

George, it may be worthwhile trying to knock a bush out - sometimes there is meant to be a hole drilled through which one of the highly skilled technicians at the factory forgets to do.

Michael

Hi George,

If its just a couple of oil galleries you might find it helps if the shafts are turning to move the oil from one bush to the other.

You have the leadscrew shaft out now, can you see any holes in the bushes?

Stuart

Hi guys, sadly no oil holes are present in any of the bushes now visible. It is interesting (if not sad) on the shaft that drives the lead screw, there is what appears to be a thrust race and bearing sleeve. The bearing sleeve has a hole drilled through it that appears to be for lubrication, but there is no hole in the casting surrounding it.

The shaft still in the box I haven't removed because the bushes have been pushed in pretty tight (the only B thing on the gear box that was tight) and I have avoided putting too much pressure on anything at the moment.

All input greatly appreciated
George

Originally Posted by georgedgerton

Hi guys, sadly no oil holes are present in any of the bushes now visible. It is interesting (if not sad) on the shaft that drives the lead screw, there is what appears to be a thrust race and bearing sleeve. The bearing sleeve has a hole drilled through it that appears to be for lubrication, but there is no hole in the casting surrounding it.

All input greatly appreciated
George

Hi George,

That thrust washer setup sounds similar to my CQ9325 - it's supposed to be greased annually - Ha Ha fat chance of that, as you have to disassemble the quick change box to access it. So I just overfill the g/box massively and it finds it's way to that OK and seeps out the leadscrew bush slowly

But you can't do that as the leadscrew is too high.

Could you drill those top two bolt boles through the bushes and remove the bolts and squirt a bit of oil in there occasionally ?

Rob