Making an Engagement Ring (February 2017)

I've finally found the right person to spend the rest of my life with and I thought making my own engagement ring would be a fun project and mean a bit more than a store bought one. I've always documented my hobby projects in pictures, but I thought it would be cool to film this one and make a video of the whole process.



I decided to machine it out of a solid block of titanium rather than trying to learn how to do gold smithing in month. I spent a few evenings designing the model and coming up with a plan to tackle the machining and work holding. The bore is .650" (size 6), wall thickness is .035", width .050", and the diamond is .295" (7.5mm) diameter rose cut. The diamond is held onto the ring with a bezel mounting. Basically it sits in a .015" deep cup and the .005" thick edges get peened over.

Titanium Engagement Ring


Top, front, side, and perspective.

Titanium Engagement Ring


And finally here's an overview of the steps necessary to machine the ring. The only special tools I'll need other than the lathe and mill is a boring head and rotary table.

Titanium Engagement Ring


First I drilled a pilot hole and hogged out the bore of ring with a 5/8" drill.

Titanium Engagement Ring


Next I bored it out from ~.625" to .650" which the ID of a size 6 ring.

Titanium Engagement Ring


Then I parted it off .350" wide. This will leave me enough width to form the cup that holds the diamond.

Titanium Engagement Ring


Next it was over to the mill. I touched off at the top of the ring and milled down to the top of the cup.

Titanium Engagement Ring


Next I used an edge finder to pick up the center of the ring and then I used a boring head to form a .310" OD x .025" deep cylinder. This will be the outside of the cup. I never thought about it before, but the mill has to be run in reverse since you're boring the outside diameter. I've only bored inside diameters until now.

Titanium Engagement Ring


The next operation is to bore the inside diameter of the cup, but I need a pilot hole to fit the boring bar in. So I used a 1/4" end mill to form a .015" deep hole.

Titanium Engagement Ring


Then I could come in with the boring head again and take the cup up to .300" ID. My diamond is .295" in diameter so this should leave just enough slack. I find it hard to adjust the boring head accurately, so it's best to sneak up on the dimension in multiple small passes.

Titanium Engagement Ring


Now that the cup is formed it was time to mill the band down to .050" thick. I spent a long time thinking about how to set this up. I knew I'd need the rotary table for the next operation so I wanted to get that set up now. Eventually I decided to drill a pair of 1/2" holes through an old 4 jaw chuck and bolt that right to the rotary table. Then I mounted the ring on an expanding mandrel and took both sides down to .025" from the centerline. This left the band .050" thick.

Titanium Engagement Ring


Finally the rotary table comes into play. I needed to mill the OD of the band down to .035" thick and the rotary table was the best way to do it. And by using an 1/8" end mill, I also formed some nice radiuses that sweep up to the cup that holds the diamond.

Titanium Engagement Ring


The whole rotary table setup was a little crazy and took a while. The rotary table is first indicated true under the spindle axis. Then I bolted the 4 jaw chuck to the table as close to centered as I could. There's a protruding boss on the back, so I jacked it up with some 1-2-3 blocks. Then I chucked the expanding mandrel and indicated the ring true with the spindle axis. It actually worked pretty well, although I could use 2 more bolts through the chuck. I noticed I developed a bit of chatter when 90º away from a bolt.

Titanium Engagement Ring


The diamond fits down into the cup and the edges get peened over to hold it in place. I wanted to get a picture of this operation, but my machining was so precise that the diamond clicked into place and I couldn't get it back out again. The bottom floor of the cup is .010" thick and the walls are .005". They protrude up over the flat edge of the diamond .008". It's just enough to securely hold the diamond in, but not so much that it covers up too much of the diamond.

Titanium Engagement Ring


All that was left was to put it in the box (article coming) and propose!

Titanium Engagement Ring


We drove out to the Blue Ridge mountains to a rock formation I know of that juts out over a valley. It was absolutely beautiful. The weather was in the 60's in the middle of February, the skies were blue, and we were the only ones there. This rock is about 4 miles up a dirt road that is full of pot holes and rocks the size of your fist.

Titanium Engagement Ring


Success!

Titanium Engagement Ring