# DIY CNC metal lathe build



## CNC_noob (Jun 6, 2021)

So I have almost completed my CNC metal lathe project.  I just need to finish the fine tuning for concentricness and then it is done.  See the video for part 1 of the build here:  




Here is a picture of the almost finished machine


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## matthewsx (Jun 6, 2021)

Nice, are you getting a lot of runout from the pillow block headstock?

John


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## CNC_noob (Jun 7, 2021)

John,

i don’t know that I know enough about machining to know.  I am literally learning how to set up as I go as this is my first lathe.  I watched some videos and read some stuff before building it and then redesigned the headstock a few weeks agowhen I realized my first design had too much chatter and a lot of flexing when I tried to cut into the face of a bar. It is a lot better now, but I need to get everything aligned better and do some more testing before I declare I am done. 

I’ve just started working on getting everything concentric and aligned.   One issue I wish I’d checked was that my round bar for the shaft wasn’t really round.  It was off by .01 inches but I think I can fix that by boring the chuck?  But I haven’t done that yet because I have variation from the backplate to the chuck of .015 that I want to fix before making any changes to the chuck itself.  

after I tinker with it for a few more weeks to months on my weekends I will be sure to update.

if I run into anything I cannot figure out I will post a video here to hopefully get some ideas and help from the community.

thanks for the question and sorry i didn’t answer it very well.


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## Papa Charlie (Jun 7, 2021)

Nice work. Are you using NEMA 34 Stepper Motors? What is the torque on those?


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## matthewsx (Jun 7, 2021)

I’m working on a home built CNC mill, rigidity is difficult to achieve with fabricated structures.


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## CNC_noob (Jun 7, 2021)

Papa Charlie said:


> Nice work. Are you using NEMA 34 Stepper Motors? What is the torque on those?


It is the NEMA 23.  Available on Amazon and other places.  https://www.amazon.com/dp/B00PNEPW4C?ref=ppx_pop_mob_ap_share



3Nm(425oz.in) holding torque


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## CNC_noob (Jun 7, 2021)

matthewsx said:


> I’m working on a home built CNC mill, rigidity is difficult to achieve with fabricated structures.


I agree.  I am running into a lot of vibration on face cuts but am sure I will get it figured out.


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## markba633csi (Jun 7, 2021)

I can see at least one place where the design looks iffy, for example, hanging the toolpost way out on a limb like that will almost certainly cause chatter and problems with repeatability, possibly even broken tools and bent slides. You really want to tuck that in more if possible
Rigidity is key with machine tools, and that usually requires mass and compact structure
-Mark


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## CNC_noob (Jun 7, 2021)

markba633csi said:


> I can see at least one place where the design looks iffy, for example, hanging the toolpost way out on a limb like that will almost certainly cause chatter and problems with repeatability, possibly even broken tools and bent slides. You really want to tuck that in more if possible
> Rigidity is key with machine tools, and that usually requires mass and compact structure
> -Mark


Thanks for the suggestion.  I can definitely shorten it up and tuck it in.  But it doesn’t even shake when it is cutting (I get vibration on facing elsewhere but the tool post seems calm) but if it will make it better I can definitely shorten it.  Any other design changes I should look at?  Thank you very much.


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## CNC_noob (Jun 8, 2021)

matthewsx said:


> Nice, are you getting a lot of runout from the pillow block headstock?
> 
> John


So I have done some additional testing and I can confidently state I am getting a fair amount of runout.  But I don’t think it is from the pillow blocks.  I am pretty sure my backplate and mounting  is giving me the most runout and I need to machine this a little more.  Is there a bearing system you could steer me to that would be better than the pillow blocks?


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## markba633csi (Jun 8, 2021)

Nothing really wrong with pillow blocks- the challenge is in mounting things on the spindle shaft with perfect concentricity
you almost need a whole 'nuther lathe to do it


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## CNC_noob (Jul 7, 2021)

markba633csi said:


> I can see at least one place where the design looks iffy, for example, hanging the toolpost way out on a limb like that will almost certainly cause chatter and problems with repeatability, possibly even broken tools and bent slides. You really want to tuck that in more if possible
> Rigidity is key with machine tools, and that usually requires mass and compact structure
> -Mark


Just fixed it.  Thanks for the advice.  You can see a 60 second update to the cross slide here and there are more links to short videos if you want to see the process. Thanks for the help. The lathe is cutting really good now.  A few more tweaks and I will be done I think.


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## hman (Jul 9, 2021)

Looks good so far.  But with the 4-way tool post, tool changes (and the resulting "zeroing") will take some time.  Perhaps you should get a QCTP, so you can "zero" and store the values for several tools ahead of time, then use them in succession for whatever multiple-tool lathe job you have to do.


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## CNC_noob (Jul 9, 2021)

That is a great idea. Thank you.


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