Working on fixing my lathe.

D

dave_r_1

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For some time now, I had a "problem" with my lathe, in that the power feed screw worked, but the feed for threading didn't. I had figured that I had screwed up one time and run the saddle into the head of the lathe, and broke something in the gearbox. It's a Force International ML1440GH lathe, evidently pretty much the only F.I. lathe on the internet, but it's a semi-generic clone, so I googled for other ML1440 lathe manuals, found one with a gearbox front panel that looked like mine, and figured out how to take it apart, at least to take the front control panel off to see what's up inside.

And here's the gearbox insides, and the backside of the control panel:
IMG_1046.jpg
IMG_1047.jpg

And note to anyone doing something like this, and fiddling with the control settings with the panel off like this, some of the controls use a ball-detente setup to produce a satisfying "click" feeling in the handle for each gear position. With it apart, it is possible to rotate the controls past their limits, which will result in the ball being launched in a random direction.I spent around an hour going through the crap on the floor around my workbench before I found it (I was close to just giving up and buying a ball bearing or a bearing to cut apart to use)...

So, I fiddle with the gears, and eventually come to the realization that there was nothing wrong with the lathe (at least, not with the gearbox).

Here's the threading/power feed charts and control settings panel:
IMG_1048.jpg
It turns out, I had the threading screw in neutral. If you look over the threading/power feed chart, all the entries for threading use JKLMN, while the power feed entries (two charts along the bottom), use P. From looking at the gear position you see in the first photo (top sliding gear on the right-hand side of the gearbox), that happens to be in the 'P' position, which doesn't drive the threading screw. So yay, there's no problem.

So, I can clean up the control panel mounting surface, maybe put on a bit of rtv and bolt it down, but I have two questions

1. What gear oil should I put in it. I've got some SAE10 and SAE30 non-detergent oil, but I can get other stuff if it should have something else
2. I took the arrow "covers" off the AB and CD knob (as part of trying to figure how to get the knobs off before finding out it doesn't come apart that way), and now I'm not sure which way the indicator is supposed to go for them.
 
Overall, the input shaft (driven by the motor) is the top left shaft, goes through the middle left shaft, then the bottom shaft, which is solid for both sides, then goes up to the middle right shaft (power feed) and then to the upper right shaft (threading screw) if not in neutral.

Closer photo of the gears in question:
IMG_1050.jpg
For the top gear (AB), if the sliding gear is left, then both gears are about the same size, and right, it does gear reduction.

For the bottom gear (CD), if the sliding gear is left, then it does gear reduction, but if the sliding gear is right, the output/bottom shaft is driven faster than the input (for the CD setting)/middle shaft.

Given that TPI increases as the settings go from AC, BC, AD, BD, I think that the arrows should point to
A: top gear is left
B: top gear is right
C: bottom gear is right
D: bottom gear is left

So, AC should get the bottom shaft rotating the fastest (relative to the top left input shaft), resulting in the lowest TPI, because it will move the saddle the fastest.
and BD should get the bottom shaft rotating the slowest, resulting in the highest TPI, because it will move the saddle the slowest

Does this sound correct?

I can always verify/fix the arrows afterwards, by making some test threads, but I like to know/understand how this works.
 
What was the intended purpose for the SAE10 and SAE30 oil that you have?
 
I use a 50/50 mix of it in the various ball-oilers on the saddle and tailstock.
 
dave_r_1 said:
I use a 50/50 mix of it in the various ball-oilers on the saddle and tailstock.
Click to expand...
What I am trying to ask is: What purpose was the oil originally sold for? Oil for internal combustion engines have different base oils and additives than oil for sewing machines or for automatic transmissions.
 
Last edited:
dave_r_1 said:
1. What gear oil should I put in it. I've got some SAE10 and SAE30 non-detergent oil, but I can get other stuff if it should have something else
Click to expand...
it will be dependent on ambient temperature in the shop. 30wt oil may be too thick in wintertime
i like to use AW32, AW68,& AW100 hydraulic oils when i can't find Non Detergent Oils
you may wish to consider a AW32 for your latitude, if your shop gets cold
ND10 wt would also be just fine too, if you already have it- just keep up with filling the reservoir
 
I don't use the lathe a lot, but the garage temp varies between -30C or so to +35C (maybe not all the way, because the garage is insulated), and only gets heated during the winter when I'm working in the garage.

I guess I will track down a litre or two of AW32.
 
I agree with Ulma Doctor. You could use the SAE10 motor oil, which is the same as ISO32, or even add half SAE30 for warm months. I think you would be better getting the AW32 or AW68 hydraulic oil instead. Why take chances with an expensive lathe to save a few dollars?
 
That is a very standard gearbox. I am using 32 weight hydraulic oil in the feed box on my Enterprise lathe (with the cover off it is very similar). I am using Shell Tellus 32 - I was able to get a 5 liter jug from UFA. I keep a jug each of 32, 46 & 68 on hand for the various machines.

I loaded a copy of the manual for the Enterprise in the download section. It has a good diagram of the feed box and a section on lubricant for the machine. The requirements of your machine will be very similar.

David
 
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