Concrete Metal Lathe

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Introduction: Concrete Metal Lathe

About: I'm a electronic engineering tech with massive love for DIY building, and tools that make tools.

I've wanted a large CNC lathe for a long time...key ingredient to that being a large lathe. Unfortunately most places that sell these lathes want a large sum of money in exchange. After some searching on the internet it turns out one could build a lathe from scratch using concrete and scraps of steel. This is the process of me building such a machine. This lathe is designed to be built in the most rustic conditions using minimal tools, however I have access to some better fabrication tools so I used them to my advantage. With the said I'm confident that if I had to build this beast with a hacksaw and a hand drill it would certainly be possible!

The final result is a machine that is far more precise then I initially imagined and a great machine to upgrade into my full fledged CNC metal turning monster!

It seems the Make Magazine link online was the best repository for information on this lathe but it can be hard to find. I've downloaded the complete article (which was free online to begin with) and posted it here to make life easier. I've based my machine largely on the size and scale of these plans (my lathe shrinking in length to 42" overall).

Full Spectrum Laser Contest 2016

Runner Up in the
Full Spectrum Laser Contest 2016

Step 1: The Concrete Form

The first thing to do was cut a mold and pour the lathe's main form. The form is a simple shape that could easily be cut with a table saw, or a skill saw for that manner but as I have access to a large format CNC machine I decided to design the mold in CAD and cut all the required parts (IGES file attached).

With the metal parts embedded into the concrete I installed the main bearing mount as well as the CNC cut pipe holders. Once again this is a part that was going to be simple off cuts of angle iron but access to my little CNC let me get fancy. This is the modification that will allow for continuous adjustment as the concrete slowly shrinks over time.

I've also attached a rough BOM which as approximate costs of things I purchased. I had quite a bit of scrap metal and plastic on hand so I worked the design around what I had.

Step 2: Moving the Beast

I started casting the lathe when the weather in the garage was still dropping below freezing the odd night. I decided to cast the concrete in the basement and then figure out how to move it after...which was silly.

Moving a 500lbs of concrete up a flight of stairs is NOT easy. However people build spaceships and go to space so I figured I should be able to make this happen. After a few hours, copious use of ropes and pulleys and a few extra nicks in the walls I had the lathe up into the garage.

I added some extra bracing to my work bench in the garage and once again used a combination of bricks, jacks, and car tires to eventually lift the beast up onto its new home.

Step 3: Casting the Carriage

With the weather warmer I was able to finish the carriage casting in the garage. This time I made the forms using the table saw and some scraps of wood. The metal elements were placed into the concrete while everything was still setting up.

Brass was bent into crude angles to function as wear strips for the bottom of the (heavy) carriage. At this point I could dial in a more accurate alignment of everything and start actual work on making the lathe function.

Step 4: Cross Slide Addition

After installing the lead screw for the carriage I moved onto building the cross slide. I have a milling machine so I was able to make a cross slide out of blocks of aluminum, this could easily have been made with a hacksaw, file and drill as I mention in the video...after this machine my hack sawing skills have definitely leveled up.

I used UHMW for lead screw nuts. I have used this plastic in the past on an old CNC machine and find they maintain a very low backlash drive for a long long time.

Step 5: Pulleys for Turning

Now this would be a pretty poor functioning lathe if it didn't spin. In this step I took an off the shelf shaft, err....the big black thing in the picture. I took that black thing and drilled and tapped a couple holes corresponding to the holes in the pulley. From there I could bolt everything together and have a reliable way to transmit power to the chuck.

I used fancy link belt as I figured I wouldn't be able to bolt a pulley onto a shaft by eye all that accurately but it turns out that I hit the mark perfectly and the pulley runs extremely true. None the less link belt is wonderful stuff if you can tolerate the cost.

The motor is nothing more then a 1/2HP furnace motor which works surprisingly well! The pulley ratio gives me 300-400 RPM at the spindle which suits me well for the screw pitch of this machine.

Step 6: Tool Post and 3 Jaw

Once the spindle was able to run under its own power I decided to tackle the tool post. With this built I could now start using the lathe to help built itself. First I found center on the main shaft, made note of that height and milled up a solid block of aluminum to hold a tool at that height. Once again there is 1000's of ways to do this, I built it this way to suits my needs with the material and tools I had on hand.

A backing plate was cut, trued up on the spindle and shaped to attach the 3 jaw chuck. I goofed slightly on this part and ended up over cutting the alignment plate for the spindle. I will remake this part in the future from thicker aluminum plate as it seems the 1/4" is a little small for holding the chuck perfectly true (can be seen in the video while turning the brass).

Step 7: Final Thoughts

I am very very impressed with the results this machine has been cranking out! I still have to go thru the process of perfectly aligning the ways (over the entire length) lapping the slides, rebuilding the chuck plate, casting/turning hand wheels and possibly building some way covers to protect the exposed lead screws but already its a great machine to use!

The standard threaded rods I have used on this machine mean the hand wheels feed in and out exactly opposite to what I am used to...but that will only be a factor while this machine sits in full manual mode, as I mentioned earlier the next step is to convert this creature over to full CNC control, stay tuned and thanks for watching!

-Curt

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    user

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    Really nice job! I am curious how you accounted for any axial load at the spindle - is there a thrust bearing somewhere, or do the set screws in the flange bearing take care of this? Any information you can provide is helpful. Thanks.

    85 Comments

    Awesome instructable!

    I was just doing some research today and found this technique was created by Lucien Yeomans in WW1 to make millions of artillery shells. It only took 7 hours to create a 10-ton lathe vs. 6 months for a traditional lathe. After WW1 ended, they scrapped all the lathes.

    Would it not be possible to take the same concrete base, turn it 90 degree's, and X-Y-Z table on it then mount a chuck and motor on it to have yourself a mill?

    1 reply

    Indeed it would be. Some people even mount a vertical slide on the mill cross slide table and use lathes as sideways mills...limitless options.

    Gracias .eres el mejor

    Hi, first of all I want to say thank you for putting up your awesome project!
    I'm so keen to build my own, I have been trying to open the files you have added for the MDF cuts. Unfortunately all that it displays is a whole bunch of numbers, that's all each file shows me is numbers that make no sense. Any Help accessing these files would be much appreciated. Thank You

    Thank you for the proof of concept. man
    I have similar plans for surface grinder made from lathe...

    So you work so excited me to start with those plans...

    Thank you so much dude.. I needed this to finish my own engine brand. I'm making my own engines from sand cast aluminum and junkyard pieces.

    Saved my life. I was gonna have to buy a lathe. Out of thanks, I donate you this immunity cat. The immunity cat saves you from stupid facebook chain letters.

    The best diy made (by one man only) machine I've ever seen, definitely most needed in the workshop as well, be proud of yourself man, enjoy.

    user

    Where did you get the three jaw chuck?

    Pretty brave mounting a lathe in front of a window. ;)

    1 reply

    Haha, the taig lived infront of that window for a few years so I'll take another gamble...cant beat the light!

    Do you think you could post the DXF files for the form?

    1 reply

    So sorry friend, I have not forgot about you. They reside on my work computer and I constantly forget to upload when I'm sitting at it. I'll do my best to get it up before the weekend.

    That's awesome that you've posted the IGES form file and the BOM. I really appreciate it as it will certainly help me get started making this. Do you think you could post the form broken down into pieces (either in DXF or PDF or similar format, instead of as a solid model) for easier loading into CAM software for milling?

    How important do you think the rebar is? Would this project work if you didn't embed rebar, or is it critical for structural integrity? Thanks!

    5 replies

    Thanks! I'll be sure to upload the dxf files of the cut sheets, its fairly specific to my build but would be a nice starting point for others.

    I'd say the rebar is important, it would probably still work but the chances of it fracturing under a shock load are higher (probably only something you would encouter moving it around). Even dropping in some wire mesh, or fiberglass fill would probably work just as well if not better then rebar.

    I appreciate how open you are about this project. I'm looking forward to seeing the DXF's.

    I plan on building a machine like yours, pretty much exactly as you built yours. I don't see any reason why that wouldn't work, although I'll probably use styrofoam instead of MDF to make the form. Your build seems to have worked out so great, and I've already found suppliers for almost all the important parts. I'll build it right on the workbench where I plan on leaving it for years to come so moving won't be an issue (although I was looking forward to spending a whole day attempting to move it, just as you did). Where did you get your motor? Can you provide the model/wattage/size/any other identifying information you can find for it? I'm trying to find one from the appliance recycling centre from a dryer or something (hopefully get it for free). I need a lathe in the next couple months or so, and this looks like the best option by far, so I'm quite excited to begin toying with the plans (I was going to try to aluminum cast a much smaller version, but this appeared out of nowhere right before I was going to get started designing the basic aluminum version I had in mind). Thanks!

    Don't underestimate the weight of the concrete - it can break your styrofoam. Plywood is a smarter choice.

    Thanks! I am open about the design because its based on an open source machine: https://concretelathe.wikispaces.com/00+-+Introduc... . Just remember that if your making your forms from foam you might have an issue with pressures inside the mold, 500lbs of concrete can exert a decent amount of sideways force, I was worried about my mdf mold breaching during the final tamping.

    The motor I used was a cheap 1/2 HP furnace motor that I picked up from a local buy/sell site. If your going to use the lathe for big turnings 1/2HP is a little anemic but workable with light cuts. Be sure you have room to mount the motor in both directions, or are able to reverse the direction it runs (I electrically switch the direction of rotation to suit my mounting position).

    Thanks for the comment!



    Just noticed you haven't uploaded the dxf files yet...do you know when you'll have a chance to do so? Thanks!