Cutting a switch knob from 6061 aluminum using a CNC mill as a lathe

This is a short video of my CNC-converted Grizzly Mill-Drill (Sieg Super X3) being used as a lathe to cut a switch knob for a PDP-7 computer. A 3/8" 6061-T6 aluminum bar about 3" long is mounted in a collet in the mill, and is driven past standard lathe tools mounted to the mill table. The spindle is running in reverse direction due to the orientation of the tools. I created a G-Code program by hand to make the two different tapers and cut off the knob at the end. Depth of cut was .010 because heavier cuts caused the rod to deflect too much. Spindle speed is about 800 RPM; cuts were made at 3 inches/minute except for the final cutoff, which is about .3 IPM.

UPDATE:
I have received a good number of questions about the videography. I used an HD camcorder (Sony HDR-SR11) which captures in AVCHD format. YouTube will not accept AVCHD video, so I used a program called Free HD Converter from Koyotesoft.com to convert it to MP4 at 1280x720 resolution; which I was able to upload directly to YouTube. Not much work all told, and the results speak for themselves. Of course, good even lighting and using a tripod are key to getting good video.

Category:

Howto & Style

Tags:

• CNC
• Mill
• Grizzly
• Sieg
• Super
• X3
• SX3
• CNC Fusion
• Lathe
• PDP-7

[WingChunLover2]

Is the component holding the piece a typical jaw chuck, or did you just shove the thing into the collet?

[devers6]

@WingChunLover2 Yes, it is being held by a 3/8" collet. Far less runout than with a chuck, although I do have an R8-mounted 3-jaw chuck to hold larger pieces as seen in my other videos. I had been initially thinking of having the collet grab the stock automatically using my pneumatic drawbar, but I figured by the time I got all the kinks out of that with the additional programming, I could just do all the parts manually mounting them - and I did.

[devers6]

I did 20 of them in an afternoon, all exactly the same. I did them for fun, for free, for some friends. That's the point. If you don't want to come across as a hater, maybe you should just think twice about opening your mouth.

[cooks9]

Also. I know nothing about the whole CNC lathe thing but I was wondering how you made the machine cut the shapes you wanted.

Do you program the movements with a computer?

[devers6]

Yes, there is a computer controlling motors for the X (side-to-side), Y(front-to-back) and Z (up-down) motion. A program called Mach3 controls these axes in sequence and in sync, using a series of commands called "G-Code" to direct the cutting of the necessary shapes. Home CNC is a rising hobby with many companies offering low cost components to help create these machines. I find it quite rewarding to have a machine that I can control so precisely and with so much versatility.

[JohnGrimsmo]

As the other guys said, extremely high quality filming! Reminds me of the GlacernMachineTools channel. Very neat how you converted the X3 to a lathe, although you should be able to spin that part waaay faster than 800rpm. On my lathe I'd run it at full speed, 2400rpm. Great job though!

[devers6]

What a kind comment! I have recently found the Glacern web site, and to be compared to them in any way is most flattering. I am really just an accidental videographer (if it's good, it's an accident); but I try to concentrate on lighting and using the camera on a tripod to make the videos easier to watch. Glad that the effort is appreciated.

[Ray262626]

nice job on the part and the video. I made a new video for my website miloeng.com.

I wish I would have used your video skills. -Ray



[dav1dh0ff]

how have i never seen this cutting strategy before?! brilliant!

[W4llyB4nger]

Very cool.  way to think outside the box.

[Bigwingrider1800]

Yea dont worry about the negitive (haters). well done. i was doing that 20 yrs ago on a manual mill (just step pins). looking to get a machine.do you still like it? and if not what would you get? thanks

[motogpphil]

I dont mean to just come across as a cyber hater, but may I ask whats the point?

I could make thet in not much longer on a manual lathe.

As JohnGrimsmo said not enough speed, not enough feed to break the chip and too small cuts.

So why?

[nitronovice]

first time i've seen a mill used that way!

just started machining at school, and i'm loving it :)

[jtjoser]

Nice thinking of using the mill as a lathe, I never thought of that! Also, great job on the recording!

[powaybob]

Cool! I used to write Fortran II for a PDP-7. 1968 I think. Frankly, I don't remember the switches. By the way, the point of your cutoff tool should be reversed. The longer tip should be against the part.

[cooks9]

Like a laptop computer or some kind of integrated computer?

I have a growing interest for a machine like this and this is the first and biggest question I have.

[cooks9]

May I kindly ask how you got that kind of clarity in your video? I have an HD camera and when I download footage on to youtube it makes it very low quality.

I thought youtube was supposed to detect if the video was HD or not.

[chrisjh777]

Great Effort!!! Great photography. What is tha part number of the trigon inserts? I need to get some.

Regards chrisjh777.

[kinglonewolf104]

Cool video. I liked the bit where you zoomed in at the end to show the precise cutting.

&eB

[YoungJim409]

Thanks for putting some effort into the cinematography. There are many videos of people making neat things like this, but whose videos are blurry/shaky/filmed with a cell phone, and unpleasant to watch because of it.