View Full Version : Shiny project finished yesterday.

10-21-2013, 12:05 PM
Even though the CWR (cost per widget ratio) was astronomical, I felt very happy finishing this project yesterday. The CWR was high because I used the nearly completed ORAC CNC lathe to make it along with my first successful use of Dolphin Partmaster lathe CAM. I’ve been struggling with Dolphin on & off for quite a while but there’s nothing like a project promised to a good friend to get me stuck into tackling the unknown.

Good friend needed a replacement knob for an old cooking pot he inherited from his grandma. It’s an Italian thing I guess. It was an old gray enamel pot grandma used to cook the “gravy” back when he was a tyke and the memory of the smells & tastes from those days meant a lot to him.

The original knob cracked & split so he brought it to me and said “Can you make one of these out of aluminum?” I said sure, piece o’ cake for my CNC lathe. After many more hours than I want to admit were spent cussing Dolphin & Mach3, the light finally switched on in my brain & I was able to tell the tools where to go without running into anything. Now I think I can use it as a useful tool. (Yay!)

Had a couple problems though. I think I had the speed too high on the finish pass & got a little smearing on the front surface. Also, when I tried to unscrew the finished knob off it’s arbor, I realized it was way too tight and wouldn’t come off. Ended up having to use a parting blade to slice the arbor down close to the stud to get it off.

http://i57.photobucket.com/albums/g227/DBAviation/T_KnobBlank_zps2b5336bc.jpg (http://s57.photobucket.com/user/DBAviation/media/T_KnobBlank_zps2b5336bc.jpg.html)

http://i57.photobucket.com/albums/g227/DBAviation/T_KnobFrtCut_zps346cffa3.jpg (http://s57.photobucket.com/user/DBAviation/media/T_KnobFrtCut_zps346cffa3.jpg.html)

http://i57.photobucket.com/albums/g227/DBAviation/T_Knobs_zps59b1ba34.jpg (http://s57.photobucket.com/user/DBAviation/media/T_Knobs_zps59b1ba34.jpg.html)

10-21-2013, 12:29 PM
...Also, when I tried to unscrew the finished knob off it’s arbor, I realized it was way too tight and wouldn’t come off. Ended up having to use a parting blade to slice the arbor down close to the stud to get it off.

Nice. To get around the tightness at the end problem I would have used a piece of stock maybe 3/4" to 1" longer. You could still pre-drill to get the thread in place but you'd have a short stem to grab in the chuck. A final parting cut and you'd have the same result...

10-21-2013, 12:35 PM
Look good but remind to use a pot holder or he'll think of you everytime he burns his fingers.

10-21-2013, 01:08 PM
Look good but remind to use a pot holder or he'll think of you everytime he burns his fingers.Yup, my thoughts;) exactly. He's using it with a bolt now so I'm thinking he's educated himself already.

10-21-2013, 01:55 PM
beautiful work, some funky radii too!

10-21-2013, 02:37 PM
Thanks Matt. I've done everything with Mach turn wizards 'til now but I couldn't on this one. It was real simple to draw up the profile in TurboCAD and fairly simple in Dolphin once I got my head around how it works. New software just gives me the willies. The youtube tutorials move so fast I missed a few key points. Once I started using the help files in the program, things started making sense.

The knob needed only 1 LH and 1 RH turning tool and I chose to do the rear cut 1st then the 2nd using 2 separate G-code sequences so the part (and I) had a chance to cool down a bit. Other more complex projects will have 1 long sequence with whatever tool change commands are needed in the code. I set up Mach to stop the spindle at each tool change command and wait for the Cycle Start button press before proceeding. Wish I had an ATC but the QCTP works well.

I'm still amazed at how well the tool table thing works. As long as the axis homing is accurate and the tool offsets are set precisely, the dang thing hits a size within a thou or better....today, tomorrow, next week, whatever. I do have to creep up on it when changing between steel & aluminum but overall I'm real happy with it. I giggle like a schoolgirl every time I make a part & measure it. SWMBO thinks I've lost my marbles.:)

10-21-2013, 04:02 PM
software gives me the heeby jeebies too, I just don't think that I'm wired that way :) I've been wanting to write my own flashlight driver programs which is theoretically simple, but practically terrifying.

Your CNC build is really impressive (you have a long thread about, right?) and it's great to see it spitting out parts. I think better halves/ SWMBOs etc have a built in verbal pat on the head in response to our garage victories - it keeps us happy and lets them watch The Voice without someone next to them complaining how pointless it is. Win win all round!

10-21-2013, 05:40 PM
Thanks Matt. Yup, long thread for sure. I think I bought it March of last year and I've been investing the majority of my spare time on it ever since. Still not finished with it though! The shiny knob thingie was just a sidetrack from the latest addition that's soaking up tons of time....a reduction belt drive system to increase the torque & speed stability for better threading.

The Voice! That's funny, guess what I have to do on Monday nights.:rolleyes: A small price to pay for peace & domestic tranquility though.

10-21-2013, 09:39 PM
The knob turned out nice Milton

I can play with my Orac lathe for hours. Most fun machine in my shop.

10-21-2013, 10:54 PM
Most fun machine in my shop.

JimNext time I'm piddling with the little Denford Micromill, I should engrave a little sign with that on it & stick it on the lathe in plain sight. Every time I panic & slap the E-stop button yelling "Why the heck did it do that!" it'll help me get the smile back on my face quicker and figure out what I told it to do that was wrong. It's done some crazy things that turned out to be my fault every time. The more I use it though, the smarter it's getting.;)

...and thanks, my buddy really likes the knob.

Jaakko Fagerlund
10-22-2013, 03:59 AM
So...no polishing your friends knob? :D

Joking aside, the smearing you said happening is a material buildup on your tool or a chip caught between the work and tool. I suspect the former, as I didn't notice any mention of using coolant/lubricant. It really helps, especially in aluminum, and most importantly your workpiece stays cool so all the dimensions are even easier to hit spot on :)

10-22-2013, 09:50 AM
I figured if I floated that one across the plate someone here was bound to knock it out of the park!:rolleyes:

Yep, flood coolant would be really great but would be hard to add to an ORAC since the lathe sits on top of its control cabinet. It does have a homemade pump that drips cutting oil on the work but I had it shut off due to the oil slinging everywhere. This was the largest diameter work (almost 2") I've done so far and the knob's shape made it a dandy oil slinger. I plan to add a shield later to contain the oil stripe.

For this job I should've rubbed an oily chip brush on it or slowed it down a bunch. I'm finding that the published speeds & feeds for cutting aluminum with carbide inserts are way too fast for my style of work. I'm not in a that big of a hurry and won't be doing production work.