King TD-45AA lathe apron modifications

[ilya]

About a year and a half ago, I bought an older Taiwanese 12x36 lathe, marked King TD-45AA. I proceeded to take it apart for cleaning and inspection and for the most part I found it to be in good shape. When the time came to work on the apron however, things began to look more grim. Firstly, the feed worm gear was completely destroyed, likely from lack of lubrication.



Secondly, the backside of the apron casting was open, i.e. there was no provision for filling it with oil to facilitate gear lubrication. The apron gears had previously been lubricated by grease and it did not seem like it's been ever changed. The apron sat on my workbench for a few weeks as I pondered what to do. I wanted to improve this design within my meager skillset. Eventually I decided to work on enclosing the apron in order to fill it with oil, similar to how it's done on other Taiwanese lathes, such as Jet and Grizzly.

I started to plug and cover openings in the apron. During final assembly, I'll also add RTV sealant.



As I'm making progress, some of the details of this apron conversion remain unsolved. I don't have a background in mechanical engineering and it takes a lot of time to find the answers as I browse through this very helpful website and of course, YouTube.

Among other things, I still need to figure out:
1. Oil drain plug / oil level gauge. I'm leaning towards a very elegant solution proposed by Wobbles, here on hobby-machinist.
2. How much oil to fill in the apron, i.e. what's the minimum amount that would allow the oil to travel up the gear train and ensure good lubrication.
3. How to lubricate the spinning shafts in the apron that are located above the oil level. It would be great if I could wick oil up from the bottom, but I may have to add an oiling cup at the top, from which copper tubes or oil wicks could be run to the bearing journals.
4. How to lubricate the feed worm. I may add a sheet metal cover to the feed worm bracket to reduce the amount of swarf that gets there. Possibly also an oiling cup at the top with a copper tube to direct oil onto the worm.
5. Finally, where to get a replacement feed worm / worm wheel. I already tried a worm from Grizzly G9249, but it didn't fit.

 

[markba633csi]

You are braver than me taking on a job such as enclosing an apron- Tough containment problem
As far as the replacement parts you might have luck checking with some of the domestic gear suppliers like Boston gear, Martin gear
and others- Another option might be to replace both worm and wheel together with Grizzly parts and make the required changes to fit

 

[ilya]

I neglected to mention that I already have a Grizzly 9x20 lathe, so I'm not in a great hurry to complete these modifications.

Another improvement that I'm considering is a provision to add oil to the lathe ways under the saddle. A fairly straightforward arrangement, based on what I've seen, involves drilling vertical holes in the front and back of the saddle, directly over the v-ways. From the top, these holes would be covered either by ball oilers, or oiling cups. From the bottom, pieces of felt would be stuffed into the holes.

 

[pigpen]

A common strategy for lubricating apron gears on mini lathes is to just grease the heck out of them and bolt a thin piece of plexi to cover them and keep out contaminants. Seems like you have plenty of room on your apron for mount points and it would be way way easier than trying to contain an oil bath.

 

[ilya]

A common strategy for lubricating apron gears on mini lathes is to just grease the heck out of them and bolt a thin piece of plexi to cover them and keep out contaminants. Seems like you have plenty of room on your apron for mount points and it would be way way easier than trying to contain an oil bath.

I already have a piece of 12-gauge sheet metal for the apron back cover. At this point it's just too tempting to continue on the oil bath path, but using grease would be a great fallback option if the apron proves to leak out all of the oil in a day or two. I plan to do extensive bench testing before installing the apron back on the lathe.

 

[pontiac428]

My lathe is in a different class, but it has an oil pump that fits inside a fairly compact countershaft that is in front of, parallel to, and driven by the worm gear. It only pumps when the carriage is being driven by the drive spindle, but a little dab'll do.

One could also make a dead simple plunger pump with a primitive ball check valve and run it off of an eccentric cam from one of the moving parts. Basically think of it as an oil can pump, configured to fit wherever you can fit it. I think the handwheel shaft would be ideal since it is permanently engaged with the rack gear, so whenever the carriage moves, oil moves.

Just ideas here. Depends on time, resources, and inclination as to whether or not it's good advice for you.

I think you will be able to make the worm gear by threading on the lathe with a profile bit, then cutting the drive gear on the mill with a dividing head.

Edit: Your worm has no coaxial spur gear, so even easier to do, no mill needed.

 

[ilya]

Made some progress down this road last week. The metal sheet I'm using is a top cover from an old filing cabinet, seems to be about 12 gauge. Two edges are factory, and the remaining two I'll have to trim on a mill. I drilled and threaded a bunch of 3mm holes in the apron. To mark the centers of the 2 large holes, I had to turn a couple of bushings from scrap, center drilled to accept a 1/2" transfer punch. The material is thick enough to fit a 3mm countersink screw head.

For sealing the joint between the apron and the lid, I'm planning to use RTV silicone along the seam, plus Loctite 243 in the drilled holes.

I came across a detailed video of a South Bend 13" lathe apron on YouTube. It has an oiling system similar to what I'm envisioning, i.e. oil in the bottom of the apron that is carried up through the gear train. The gear shafts are lubricated by wicks from a trough in the top of the apron. The trough and the sump are filled via flip top oil cups on the front surface of the apron. It was very encouraging to see that it's an existing, working design.

 

[ilya]

At snail's pace but moving forward. Made an angled hose barb which is going to screw into the apron sump and with an attached clear hose will work both as an oil level and a drain.

 

[ilya]

I made the first mistake on this project while cutting the female threads for the drain/level hose barb in the cast iron apron gear cover which will be the oil sump. A classic off by a millimeter error on the tap drill size .

I fixed it by making a shoulder sleeve, which provided an unexpected benefit: I could precisely control the angle of the hose barb without any additional effort.

The sump is now assembled with RTV. As soon as it cures, I'll do an oil-tightness test of this component.

 

[ilya]

Not too many updates to post. The sump proved to be oil-tight, much to my satisfaction. The next job I'm focusing on is making a small reservoir for oil in the top of the apron from which wicks would feed it to rotating shafts, feed worm, and the half nut. The space where it would most naturally fit is about 1" x 2" x 2.25" deep. Perhaps I've watched one too many Blondiehacks videos on YouTube, but I'm thinking of annealing a 1" copper pipe end cap and hammer forming it into a rectangular shape.