Concrete Lathe Adventure

[Tom Dunn AL]

Newer Member, first post...

Okay, I readily admit that I have no business designing a lathe, when I have very little experience using one. But, I want one and economics dictate this is the means to get one. And, I very much enjoy the DIY approach to matters and the learning curve associated with it. So, being greatly inspired by Mark Norman, I am cobbling together the Concrete/OpenSource/Multi-Machine bed approach with Gingery style aluminum castings done from Lost Foam models and a trailer axle hub and spindle head stock idea that I saw on YouTube.


My first design is not to intended to meet all needs, or desires. I just want to go through the learning process(es) and end up with a small, usable unit that I can play with and learn on. It will, however, have enough muscle and versitility to do both metal and wood turning (1-1/4" Spindle and 3/4 HP Motor.) See jpeg. I will make the components portable, so that they can be reused later in more advanced designs. All that will be lost is the concrete in the bed... that's less than $12.


This design has an 8" swing and 17.5" from the face of a plate mounted chuck to the end of the ways. The distance between the centers will depend on the tailstock design. I plan to use a threaded rod coupling, an old drill chuck and more concrete for that. The ways will be of bed frame angle iron that I have on hand. The unit will come in under 250 lbs, sans the motor, which I will mount remotely.


So far, expenses have only been $53 for the Hub and Spindle, plus I will need the $12 of concrete. Most everything else will be items I already own, or from scrap. I think I can easily bring this lathe to life for $100. I already have the motor.


Finding a used lathe has been a long term bust. I would greatly appreciate your input and help to bring this idea to fruitition. Mostly, I need help with any specifications that would make it more useful... As an example, maybe you would think that I don't need 8" of swing, if say 6" would cover 95% of common turnings, but I could really use two more inches of way length... That kind of information would be great.

One thing that really has me wondering is how the ways are trued to the spindle. I am casting mine directly into the bed to save a little money, so I have to get this right on the first try. Also, as I will be using the lathe to build the lathe, I will need to know how to turn down the end of the spindle to take the chuck plate. I have plenty of rebar to throw in, but I will not be using threaded rod to create compression, again, to save a little money.


So, I am hoping you will come along for the ride and help me out!

Tom's Idea.jpg

[Thomas Canfield]

With the arrangement you show for the bearing/shaft bolted to the concrete frame, you can shim it some to help with alignment. I think that the bearing/shaft arrangement will result in deflection with the drive belt and then the turning piece extended so far from the bearing. A double bearing arrangement with the drive on the outside or between bearings would be much stronger. What will this be mounted on? The height shown will need to sit on a strong stand to get the center to a suitable turning height.

I would go with the larger clearance over bed length. It is somewhat easy to add length, but almost impossible to add clearance.

Used lathes are hard to find, but this looks like a major task that will end up costing $ with all the details, and getting the accessories will be next to impossible to find and you will be making those.

[Mike Cruz]

Tom, I feel you...I really do. This is a huge undertaking, but when you like the journey, there's nothing like it.

Your skills are way above mine, but I do have a question for you, since I am more savy WITH the lathe than building one... When you say an 8" swing, do you mean 8" from the spindle center to the bed, or do you mean 4" from the spindle center to the bed? 8" from the spindle center to the bed is what is referred to as a 16" swing. If that is what you are planning, then yes, 16" will likely do you fine. However, I would say that to keep you from having to go through this whole process over again at a later date, I would increase the swing to 18-20". That way, you'll only have to do this once... Best of luck to you!

[Tom Dunn AL]

Thanks so much to both of you for your help!

@Thomas: Good suggestion with using shims. But, I guess my real question is "How do you take the measurements between the spindle and the ways? A squaring tool of some sort? Measurements? Your observation about deflection is keen. But, this trailer hub set up is being used on a precision metal lathe with success and acceptable run out. These bearings are design to handle significant lateral load, also. And, the back of the hub is embedded in the head stock concrete, adding even more rigidity. At 250 lbs, I can make a beefy 2x4 stand that will handle the weight, but a concrete stand would be much more rigid. Mike concurs with a greater height over the ways. That's easy enough to design in at little extra cost. Yes, I will have to make all of the accessories. YouTube for "Lost Foam" to see how I plan to accomplish that. I am keeping my expectations low. If all I end up being able to produce is file handles and Christmas tree ornaments, I will be a happy clam!
@Mike: Thanks for the clarification of the terminology. Yes, 8" over the ways, for a 16" swing. Can go up a bit, easy enough.

I have been considering embedding the trailer hub back 2" into the face of the head stock. That will put the leading edge of the hub even with the face of the head stock and gain two more inches of usable way length. My only concern is that I am reducing the amount of concrete behind the hub. I just don't know what the effect might be. I have already cheated the Open Lathe/Multi-machine head stock design down from 12" to 8". But, I don't plan to do anything nearly as heavy as that full-size lathe is designed to handle.

[John Keeton]

Tom, I have no engineering background, so my input in that regard is worthless. The one concern I have is the flow of chips and shavings into the belt drive. With the drive open and in close proximity to the chuck, this seems problematic. At the very least, it could make for a bumpy drive, and worse, a jumped belt.

[Tom Dunn AL]

John, that is a great observation! Note to self, add a cover over the belt. Actually, a sheet metal "box" attached to the rise of the head stock should do the trick...

[Rodney Walker]

If you're still in the planning stages, give yourself the extra capacity. It's a lot easier to turn something small on a big lathe than something big on a little one. You may consider additional length as well unless you're certain you just want a dedicated bowl lathe. Judging by other lathes I've seen, you can go out to about 3 ft length with angle iron rails. I don't think I've seen any longer than that so I'm guessing after around 3 ft deflection starts becoming an issue.
If the funds are available, consider having morse tapers bored into the head and tail stocks as well, or at least design them with the possibility in mind. Many lathe accessories are designed on a morse taper and you may find it more ecomomical in the long run to not have to start from scratch every time you need a new accessory.
Looks like a fun project.
My two cents,
Rodney

[Tom Dunn AL]

Rodney, you are a big help. Morse tapers are in the bigger picture. The head stock spindle will be bored in place. That's part of the lathe-building-the-lathe approach. The tail stock will likely also be cast from concrete. If so, I have seen instructions on using a Morse taper insert/receiver cast in the concrete. I just need to leave a hole for the taper tool and weld a washer flat on the back end of the receiver to keep it from pulling out of the concrete.

I would like to know if the taper will cause the chuck plate to sit forward of the face of the spindle. If so, how much? Thomas's concerns about deflection might need more consideration.

If the taper does significantly increase the spindle length, then I may be pushed to recess the hub back into the head stock to maintain the useful bed length. Then, I am back to the strength question. I am still giving consideration to increasing the swing height and way length. But, I have to keep reminding myself of the purpose of this first endeavor, to end up with a small, usable unit and learn the process. Going bigger means pouring a full bed, instead of just "legs" for the ways.

Thanks for your input, keep it coming!

[Rodney Walker]

The morse taper on the head stock end is generally for small diameter items like spur centers. Chucks and faceplates are generally attached using screw threads on the outside of the headstock. For the outside threads again it may be useful to you to pick a thread pitch and diameter that is commonly used.
Rodney

[Donny Lawson]

It sounds like your on your way to a great lathe. Looking foward to seeing a picture of it when you get it finished.

[Mike Cruz]

The thread diameter and pitch that Rodney is referring to is either 1" x 8 tpi (for smaller lathes) or 1 1/4" x 8 tpi (for larger lathes). The morse taper "hole" is inside the threaded part of the spindle, so it will not protrude any further out, or obstruct anything that is screwed onto your spindle.

[Tom Dunn AL]

Rodney and Mike,
Thank you for such great information! Yep, I was/am aware of the spindle taper and thread arrangement. I'm glad to know that Morse attachments won't add length to the setup. I am also glad to know about the spindle thread. I was going to call a chuck vendor to find out what might be common. The spindle is 1" in diameter through the bearings. Past the seal, it enlarges to 1 1/4". I am thinking of turning it down to 1", so that I can develop a shoulder for the chuck plate to sit against. From what I have read, that seems to be important. Could you tell me more about the shoulder?

[Mike Cruz]

My main lathe, a PM90, has 1 1/2" x 8 tpi threads. I think the OD of the shoulder is 2". The bowl lathe I just had built for me was done the same so that all my chucks and faceplates will be interchangeable. Not the most common, but common in my shop. It seems most of the new lathes use 1 1/4".

[Tom Dunn AL]

Thanks, Mike!

[Barry Richardson]

Very cool! I've been toying with the idea of building a lathe so I will follow with great interest! Particularly, the forming and casting of the 'crete.