# 7x12 Mini Lathe CNC conversion



## Jfong (May 15, 2014)

After converting a unimat lathe to cnc for my buddy, I decided that my own 7x12 mini lathe needs to be converted too. I had this short thk kr26 linear stage that I got for about $40 on eBay. To small for anything else but perfect for the lathe cross slide X axis. The carriage Z axis is a 10mm diameter THK ground ballscrew purchased from eBay for $115. Stepper motors are 300oz-in nema 23 that was given to me. Stepper drivers are Gecko210 also purchased used from eBay for cheap. Power supply is a diy 36 volt output from a transformer salvaged from a old broken desk lamp.

Backlash on both axis is minimal due to the high grade THK ground ballscrews. Rapid speed is set at 100ipm. I had tested it at 200ipm but thought that was ridiculously fast for such a small lathe.

Mach3 Turn running on a old P4 desktop using parallel port step/direction output.

In the video roughing pass is at 5ipm and the finished pass is 1ipm.

http://youtu.be/zuGZxvZJS_w


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## Don B (May 15, 2014)

Nice...!   Did you consider the third axis for threading? Is this something you will add later on?


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## Jfong (May 15, 2014)

Don B said:


> Nice...!   Did you consider the third axis for threading? Is this something you will add later on?



Thanks!!!

I haven't added the spindle encoder to the headstock yet if that is what you mean.  Mach3 requires that so it can read the rpm of the spindle so it can do synchronize threading. I've seen some threading youtube videos and it seems to work very well.


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## Don B (May 15, 2014)

Jfong said:


> Thanks!!!
> 
> I haven't added the spindle encoder to the headstock yet if that is what you mean.  Mach3 requires that so it can read the rpm of the spindle so it can do synchronize threading. I've seen some threading youtube videos and it seems to work very well.



Thanks for the reply, Yes that is what I meant, sorry if my terminology is off CNC is fairly new to me, I'd like to do what you've done some day but for my purposes the threading would be a must to justify the time and expense of such a project, but even with the 2 axis you've made radius and ball turning a lot simpler.)


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## Jfong (May 15, 2014)

Funny that you should say that.  I did my first ball radius turning yesterday.  I just used the Mach3 wizard to create a simple round end on a piece of scrap aluminum. I was impressed lol. 

The time spent to to do the conversion was less than a week working a couple hours a day. This has been my 6th cnc conversion so I'm getting better at it.


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## Jfong (May 15, 2014)

Some pics of my small basement metal workshop area. The gantry cnc was built last year. The smaller x1 mill has servos on all three axes.  The larger x3 mill needs the z axes ballscrew to be installed. The x and y are servos too. 

There are a couple other cnc machines that I built but they are now at my brothers place.


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## Don B (May 15, 2014)

Jfong said:


> Some pics of my small basement metal workshop area. The gantry cnc was built last year. The smaller x1 mill has servos on all three axes.  The larger x3 mill needs the z axes ballscrew to be installed. The x and y are servos too.



Thanks for posting the pictures, nice shop and CNC machines...!)


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## Blackhawk (May 15, 2014)

Very nice jfong, if you figure out threading could you help me out.


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## Jfong (May 15, 2014)

Thanks,

I have to install my hall effect sensor to the rear of the spindle this weekend.  I saw your videos but unfortunately I don't know anything about threading just yet.  I ordered some 60degree inserts from eBay today. Hopefully will have the lathe all setup for thread testing before they arrive.


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## Don B (May 15, 2014)

Jfong said:


> Thanks,
> 
> I have to install my hall effect sensor to the rear of the spindle this weekend.  I saw your videos but unfortunately I don't know anything about threading just yet.  I ordered some 60degree inserts from eBay today. Hopefully will have the lathe all setup for thread testing before they arrive.



Good luck with that, please keep us posted with your progress.)


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## Jfong (May 15, 2014)

I know this is mostly a metalworking forum but just some pics of vcarving done mostly in wood on my bigger gantry router.


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## JimDawson (May 15, 2014)

Those are great!  Thanks for sharing.


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## Jfong (May 17, 2014)

Blackhawk,

I installed my spindle index Hall effect sensor today and was very surprised that the mach3 rpm reading was within 1rpm as compared to my handheld Ametek RPM meter.  I ran some threading gcode and it seems to do what it is suppose to. I don't have a threading lathe bit so can't cut metal yet.


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## Blackhawk (May 17, 2014)

Jfong,

thanks for the information, do you think you could take a screen shot of your set up? Or maybe tell me your settings? 

Thanks


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## Jfong (May 17, 2014)

Blackhawk,
I'm going to try to grind a cutter tomorrow and cut a thread. If all goes well, I will film it and the settings I used.  I had to goto work so couldn't do it tonight.


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## Blackhawk (May 17, 2014)

Ok sounds good, I actually ground my first cutter today. Came out ok


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## Jfong (May 18, 2014)

http://youtu.be/2HpvWgHT8To




Threading works!  I made a 10-24 thread, it was a little tight but the nut did screw in fine.  I didn't do a very good job making the cutter at exactly 60 degrees and could of cut the threads a little bit deeper.  Not to bad for first time trying to do this.


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## Blackhawk (May 18, 2014)

How do you come up with the thread pitch


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## Jfong (May 18, 2014)

24 threads per inch so the pitch is 1/24=.041666.  It rounds out on the screen to .042 but put in  all 6 digits.


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## Jfong (May 20, 2014)

I received my eBay Sandvik TCMT 21.50 inserts today. They are made of cermet. They cut aluminum and steel effortlessly. I thought my valenite carbide inserts cut really well. These cut much better. I got a bunch for just $2 each. Great deal.


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## Don B (May 20, 2014)

Jfong said:


> Blackhawk,
> 
> I installed my spindle index Hall effect sensor today and was very surprised that the mach3 rpm reading was within 1rpm as compared to my handheld Ametek RPM meter.  I ran some threading gcode and it seems to do what it is suppose to. I don't have a threading lathe bit so can't cut metal yet.



Hi Jfong

This looks really interesting, I'd like to have a go at this myself.

Does the "Hall effect sensor" allow the lathe to be used with the original motor? (i.e. Manual selection of RPM and this is read by the Hall effect sensor for timing purposes)
With your setup are you starting the spindle manually?


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## Jfong (May 20, 2014)

Original lathe motor and speed control was used. I didn't modify any of that. 

All the sensor does is to let mach3 know how fast the spindle is turning. I still have to manually turn on and adjust the motor speed control knob. Now I can see how fast the chuck is spinning on the computer screen.


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## Andre (May 20, 2014)

Nice job! Now part of me wants a CNC. But I know I'll never get around to it!


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## Jfong (May 20, 2014)

Made some tool holders for those new inserts this afternoon


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## Jfong (May 20, 2014)

Andre, 

Thanks!  I've been saying the same thing to myself but instead it's a 3d printer. I want one, I just need the time to make one.


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## Jfong (May 23, 2014)

I did a simple turning last night. Small handle to replace a broken plastic one. Took about 15 minutes to do. Could never have done this manually or rather this nice looking while turning the lathe handles by hand.


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## Jfong (May 29, 2014)

Made a replacement part for a pretty old john deer tractor engine for a friend. He will tap the inside thread himself. It was nice to be able to do this.


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## Jfong (Jun 2, 2014)

Made this floating drawing pen holder out of UHMW plastic and 3/8" steel rod. A spring is used to hold the pen down for uneven surfaces. I also made a slightly larger one for bigger sized markers. Inspiration was from reading a Hackaday.com post about a neat DIY Spirograph machine. Drawing done on my gantry router I made last year. 





http://youtu.be/5jd_TfeR4Fw


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## Marco Bernardini (Jun 2, 2014)

Jfong said:


> Made this floating drawing pen holder out of UHMW plastic and 3/8" steel rod. A spring is used to hold the pen down for uneven surfaces. I also made a slightly larger one for bigger sized markers. Inspiration was from reading a Hackaday.com post about a neat DIY Spirograph machine. Drawing done on my gantry router I made last year.



This will save you a lot of time hand-signing greetings cards for New Year 
Jokes apart, a pen holder is an invaluable tool to physically materialize the tool path when working on existing complex parts which would require a lot of time to be totally digitized: better to crash a sharpie than an end mill.


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