1970's Nikken RSI-10 8" rotary conversion to cnc

[Dbsharp]

I picked up this 8" rotary that was missing a number of parts for 90 bucks! The missing parts are probably the reason it was so cheap. It appears to be in decent mechanical condition, there is less than .0005 lash in the main bearings and it feels smooth. The worm and main gear appear to be made from hardened steel and wear is nearly undetectable to my eyes, just a very small polished patch in the main gear.

I have a 400w servo lying around I'm going to make brackets for, and it looks like it would all workout pretty well. The castings on this appear to be properly rigid and I think it will work quite well for my needs. I own a business doing engineering, design, and prototyping and most of my cnc work will be one offs to low volume work. With my light duty requirements, and low hours of annual usage, this thing should last a long time unless I screw something up.

Now for my questions I hope someone can help with.

1. Does anyone have any technical manuals for this table or similar one?

2. Oil/ grease. I've seen a number of threads on this for other Nikken tables and it sounds like they use oil or grease, and I saw where one company was advising using a moly lube + being able to reduce the worm lash. Mine seemed to have grease on the main gear and worm, but oil has been found in some of the crevices during disassembly.

3. Main bearing/ seal. MY motion feels good, and there is a grease port (or oil?) for these bearings. Any reason I should crack this part open and clean? I'm thinking to just let it ride, but I'm a little worried about coolant getting in if there is a seal that doesn't exist or needs replacing.

 

[Dbsharp]

This casting has a thread on the bottom for adjustment of something (I'm guessing a brake. It looks like there is no way to seal it for oil, and I don't think there is a seal around the output plate to body. There is a very small gap between the two, I'm guessing that grease in the small gap is what keeps coolant/ debris out. There is a single lube point that feeds the middle of the bearing. If anyone can recommend a grease for this that would be fantastic. The servo will spin the worm faster than you could by hand, this is my only concern with grease.

At this point, I have a full 3d model, and a design for the components. I will machine the servo plate, cast the cover, and 3d print the splash guard. So far I have 3d printed parts to fit up, but no chips are flying yet.

This rotary fits very well on my Bridgeport boss, I think it is about the perfect size for it.

 

[eKretz]

I sure would prefer to use oil if I were trying something like this and expecting any longevity. Especially if you're hItting any real RPM. Add an o-ring or x-ring seal where necessary while you have it in pieces if possible and use oil. Even my old manual Advance rotary is filled with oil.

 

[GregSY]

My Walter rotary uses oil, too. Oddly, if you fill it to the full line, then tilt it up to 30 degrees of so, the oil comes a runnin' out. Bruh.

 

[Garwood]

The difference I see between a manual rotab and a CNC one is the CNC one is sealed and has a huge air or hydraulic brake built in.

Where is your brake?

I wouldn't bother with seals. I would just squeeze a couple tubes of JD cornhead grease in it and call it good. Maybe limit servo speed to a grease friendly RPM.

 

[macchi7]

My Moore table uses oil for lubrication and because of its design, does not leak out whether it is used in the vertical or horizontal position. Grease solidifies over time, whereas oil doesn't, or rather, shouldn't.
Nikken made very good equipment back in the day and if your speeds are kept reasonable, you will get years of use from it.

 

[Dbsharp]

Seems like most really prefer the oil. I might crack open the main bearing on this to see if I could machine in a O ring groove.

Just doing some quick greasy math, it looks like that worm would be within range for slow speed high pressure grease with a NDM of about 37000.

The brake parts on this rotary were missing, that's probably why I got it for 90 bucks. I figure I can probably do without. Both gears are steel, I would assume hardened, and there are some nice tapered roller bearings holding the worm shaft still.

 

[Dbsharp]

Well, I gave it a go and tried to take apart the bearing, but a brass screw said no.

upon further inspection, I have found a few places oil can leak from that would be hard to seal. It really looks like this was designed for daily oil lube for the main bearing, but grease for the gears and worm bearings. I think I'll just do that.




the rest
EDIT- anyone know why one photo attached at the bottom with good resolutions, but the rest are small?

 

[BugRobotics]

No idea how much use this will see but if it was gonna see coolant I'd install a small air purge to keep some positive pressure inside to reduce coolant from getting in.

 

[Dbsharp]

No idea how much use this will see but if it was gonna see coolant I'd install a small air purge to keep some positive pressure inside to reduce coolant from getting in.

Seems like a solid idea

 

[Dbsharp]

Business has been good and I have been working nearly 7 days a week, so I really haven't made much progress on this project until recently. I decided to 3d print these parts instead of machining to work through any issues first. Even with making this print on very strong settings it is flimsy, and the parts don't really align well enough for me to be happy to do much with it. I don't think I'll do much beyond testing without machining a plate.

I set the backlash to be about 20 arc seconds, and it seems to move smoothly throughout the range of motion. I know the modern nikkens go much tighter, but this driven gear is more like a helical than a normal worm.