Half-nuts -- Grease them or oil them?

I recently bought a Neuweiler Straight Line Engine Turning Machine, and I'm in the midst of disassembling it, cleaning it and putting it back together.

I have a couple of lubrication questions. First, there are some brass half-nuts on one of the lead screws, actually the cross slide lead screw. Now that gets used quite a bit when engraving with the machine. As I took it apart, it looked like this:



Seems like caked-on grease to me. So, should these really be greased, or would something like way oil work just as well, or better? It would be a fairly easy thing to apply oil to the lead screw by hand from time to time.

My second, and last question, concerns a rake and pinion that is used to raise and lower the main slide, which holds the chuck and the work piece. Everything is counterbalanced with weights, so it is fairly easy to raise and lower the slide. So, what should I use on the rack and pinion for lubrication? Oil or grease? Again, it is easy to access these, so applying any lubrication will be effortless.

Oil only no grease, just oil, any oil, way oil, even motor oil. No grease ever! Gary P. Hansen

I second the oil!!! No grease!

Ken

Aw heck!

Grease is just oil that sticks!

;-)

CalG

The one thing that is my pet peeve is to see a lathe that has a lead screw thread full of crud! Before you oil the screw CLEAN IT! Use any solvent and a brush and get the root of the thread clean and keep it that way. I always use oil. A shop I worked at had a beautiful 14" Cinncinati Tray Top that the half nuts would sometimes be hard to disengage, not good. So I turned the machine off and engaged the half nuts, then I moved the carrage crank back and forth. The carrage was able to move left to right almost the equivalent of the width of the lead srcew thread. After convincing my boss of the problem I dismantled the machine and found that the nuts were shot. New ones were ordered (high dollar) and installed. If someone would have taken the time to do what was taught it never would have happened.

I though oil became grease when the first bit of dust hit it. Seriously though I am not familiar with the anatomy of the machine but since you have it apart would their be a way to affix a small metal tube that extended from the half nut to an acessable area? That way,once assembled, it would be easy to just drop a few drops down the tube to the nut on a frequent basis. Just a thought, I have lots of them (thoughts that is) being unemployed sucks

Oil may eventually become grease, but grease becomes charcoal. I have worked on several elderly machines (80-130yrs old) where the oil cups were replaced with Alemites and packed full of grease. Usually takes a punch to remove what forms in the oil passages. Bearings don't fare too well, needless to say.

Oil on your leadscrew from here on out. And yeah, clean that stuff up real good. Many (read ALL) of the old machines I have worked on had little 1/16" copper lines running from oil ports to critical parts.

Thanks, guys. I was inclined to oil them going forward and that is what I will do.

They have been cleaned very well--they not only hit the degreaser, they lingered a while in the ultrasonic bath, too. I could eat off them, if I had something better than oil to put on them.

Still need advice on the rack & pinion, though.

Hardly anyone takes the time to clean the lead screw before cutting a thread. That is a gross mistake as the chips eat the half nuts up and especially with grease or heavy oil. It was part of my job at some shops to repair machines. After seeing the damage chips, dirt and grease or heavy oil and never cleaning the half nuts or lead screw does to the half nuts you can bet I blow the lead screw off before use and clean the half nuts as best I can.

I don't like to see any dirt on them at all. I don't lube the half nuts but I put a light coat of 30w or less on the lead screw.

There is something else that gets overlooked and thats the rack under the front way that is used to move the carriage on most lathes. It is also the method of feed for the carriage. If the rack has dirt and chips in it and the gear in the apron is contaminated as well guess what the surface finish on your part will look like as it jumps over the dirt in jerks and spurts.

My personal observation has been that most parts kept supplied with clean oil are practically immortal. It's the dirt and chips that destroy them. My Sheldon R15 lathe has a cross slide made like a Bridgeport table, a long slide on a shorter carriage that never exposes the dovetail to chips falling on it. Kind of a bother to use because the cross slide handwheel moves in and out with the slide and usually is right where I would like to stand to get a good view of the work, but the only dirt that gets on the working surfaces has to float up from underneath, so if I don't get silly with an air hose, they stay fairly clean. The rack and threading screw are exposed like any other lathe. Has anyone ever made a lathe where they are protected also? It might be especially difficult to apply to an existing lathe, but the benefits would be worthwhile.

Bill

As someone who has cleaned a few nasty lathes, a friend showed me a trick to cleaning lead screws. I was setting about to clean the rather large lead screw on my 17x60, which looked like it hadn't been engaged since it was bought. Anyway, he suggested taking a largish braided cotton cord wrapped once or twice around the thread, pulled snug (but not too snug) and running it down the thread under power. Obviously don't wrap around appendages because it can hang up and reel you in. First pass is dry and "chunks out" the worst of it, if bad like mine, use a single wrap. Then move to a clean part of the cord and soak liberally with a solvent and repeat until that section is relatively clean. Basically it will look like new after a few passes. Finally, soak in oil, perhaps with a helper to drip a little more on as you go, and make a final oiling pass. I did mine in 2 parts. Saddle to tail stock and do headstock end, then reverse. I kept a clean length of that cord in a jar with a lid and with bit of vactra in there with it. When I get ready to thread, I run that down the section of lead where I'll be threading. It removes any random chips and leaves it lightly oiled, then knock chips (if any) off, and back in the jar and on the shelf. Haven't used it much, but seems to work well.

Use chainsaw bar oil..../runs

9100 said:

My personal observation has been that most parts kept supplied with clean oil are practically immortal. It's the dirt and chips that destroy them. My Sheldon R15 lathe has a cross slide made like a Bridgeport table, a long slide on a shorter carriage that never exposes the dovetail to chips falling on it. Kind of a bother to use because the cross slide handwheel moves in and out with the slide and usually is right where I would like to stand to get a good view of the work, but the only dirt that gets on the working surfaces has to float up from underneath, so if I don't get silly with an air hose, they stay fairly clean. The rack and threading screw are exposed like any other lathe. Has anyone ever made a lathe where they are protected also? It might be especially difficult to apply to an existing lathe, but the benefits would be worthwhile.

Bill

Click to expand...

Exactly - keep the oil flowing and the muck out.

My machinery text book shows the string method to clean this lead screws

Carl Darnell said:

There is something else that gets overlooked and thats the rack under the front way that is used to move the carriage on most lathes. It is also the method of feed for the carriage. If the rack has dirt and chips in it and the gear in the apron is contaminated as well guess what the surface finish on your part will look like as it jumps over the dirt in jerks and spurts.

Click to expand...

That's something I never considered. Thanks for pointing that out!