My customer wants two Titanium necklights, one with anodizing and one in bare Ti.
First job is to make the main pieces, the battery tube and the head of the light that will hold the lens, the reflector and the light engine, which consists of the LED and driver and a metal case to hold them in place.
The two pieces at the top of the photo are the battery tubes, the bottom two are the heads. The interiors of these pieces were bored out to required diameters and then threaded. The outside diameters were left slightly oversize so that they could be turned down to their final ODs later.
The threading is o.5mm pitch. There is a technique that helps ensure smooth Titanium threads and it requires the machinist to realize that Ti springs back after a tool cuts it. Since threading involves multiple passes to get the depth of cut to the proper diameter, it is imperative that extra passes are taken as the final diameter is approached. Doing so will result in very smooth threads and make it almost impossible to gall the threads when twisting the pieces together.
Both pieces have vertical grooves and circumferential grooves that were cut with a 90° included angle cutter. Here one of the battery tubes is mounted on an expandable collet and the collet is inserted into a rotary indexer. The rotary indexer is on top of another rotating base, so that the battery tube can be milled either perpendicular to the axis of the battery tube, or parallel to the axis. The photo shows the completed circumferential cuts and now I am drilling a hole that will used to insert a split ring when the light is finished.
Now, using the same set-up, but changing the cutting tool, I am cutting some ‘dimples’ into the battery tube–basically one for each square that the grooves have outlined. You may notice that there’s some cutting fluid on the piece–that prolongs tool life and results in smoother finishes, too.
The battery tube now has its grooves, dimples and the drilled hole for the split ring.
Stepping back a bit, this shows the set-up for milling the tapered end of the battery tube. Again, the battery tube is being held by an expandable collet that is in the rotary indexer. At the far right you can see the dividing plate and below that the worm gear that rotates the collet. In the spindle is an end mill and the battery tube will be pressed toward that cutting tool, while simultaneously turning the rotary indexer by hand. With a 40:1 ratio, that results in a rather smooth feeding of the uncut Ti into the flutes of the end mill.
The early cuts are made using a roughing end mill, and then later a finishing end mill will be substituted so that a smooth finish can be achieved.
And the battery tube after the milling. There are some rough edges to be seen on the piece, but those are removed later when the cross slide is back in operation for just turning operations.
Now, lets’ see the sequence of operations for the head of the light–pretty much the same as for the battery tube:
Since the head of the light is longer than the battery tube, a longer end mill is used to cut the circumferential grooves. Mind you, you might think that cutting five or six of these grooves wouldn’t be that much work, but the fact is that one can’t cut to the final depth in one rotation–that would generate too much heat and result in work hardening the Ti–basically turning it into scrap metal. So, each groove took about four passes to complete.
Then the piece is turned perpendicular to the spindle so that I can cut the axial grooves. Now you can see the hand crank used to turn the indexer. The holes in the plate allows for a wide variety of divisions of a circle; I have multiple plates, although I find myself using only a couple of them most of the time.
Close-up the cutting tool making the axial grooves.
Then the end mill is changed to a ball nose mill and the dimples are added. Let’s see, eight dimples per row and six rows equals 48 dimples. It does require a bit of concentration when doing this operation; it’s easy to let your mind wander while feeding the piece into the tool and that’s not good.
Then a few other operations:
Here the bevel to the lens is being cut in the head. Notice that there’s a thin cylinder of metal around the piece–that’s just cut out of a soda can and it helps hold the piece concentric to the spindle, especially when the collet size is a bit larger than the OD of the piece. In this case the piece is 15.24mm in diameter, but the collet is 15.50mm, so that aluminum shim makes up the difference.
Here I’m cleaning up the sharp edge left from the end mill when was cutting the circumferential groove on the battery tube. This tool just cuts a 45° chamfer, which matches the edge left by the 90°-included angle cutter.
And now we have two fairly complete Ti necklights. Still need a few more things done to them though.
Since one necklight would have anodized dimples, I first covered most of the light with nail polish. BTW, the two pieces, the head and the battery tube, have been screwed together, with a lens in the head and a Delrin rod inside the light, along with the O-ring between the two pieces. That means that no fluids will enter the interior of the light while it is being etched and then anodized.
This is what the light looked like after the anodizing. A soaking in some acetone took care of the nail polish and then the light was turned down on the lathe to get this:
I like it, how about you?