Using 1.5" Dia. stainless steel shaft stock from a marine pump, I lathed out a Jigger/Pony Shot Glass, which is a bartender's measuring glass for shots. Jigger = 1.5oz, and Pony = 1.0 oz. I do not know what kind of steel it is, but I imagine it had to stand up to saltwater, so Im just going to assume its good enough. Its the only stainless steel we had laying around in the shop anyway.
The walls of the shot taper from ~1/32" to 1/16" to lessen the weight and give it a bit of depth. Also, 1/4" wide shallow groves were machined in it as well to make it look nicer. The concave cut in the middle gives your thumb somewhere to hold on to, and it drastically lowers the weight.
I apologize for the dirty paper, I used it while I was machining to make sure I took the correct cuts.
Step 1: Cutting and Drilling
I am sorry about not having any pictures for the drilling process. I decided to document this after I finished drilling.
-Obtain 4-6 inch section of 1.5" dia. stainless steel
-chuck the piece in a lathe, face one side to make it flat
-take an array of drill bits, starting around 1/4" up to 1-3/8", with increasing increments of 1/4".
-Drill out the cylinder with each drill bit, going up one step (this makes it easier on the bits and prevents the bit from possibly catching in too much metal and thus turning the piece within the chuck, BAD.
-Lathe speed should be between 100-215 rpm
Step 2: Machine Center Concave Groove
This step was kind of eye-balled.
Blue dye was applied and three lines scratched into the dye. The outer two lines represent the boundaries where I can not make any cuts, and defines the area of my concave groove. The center line is so I can make my first deep cut with a rounded bit. Then work down at the edges by hand while trying to match the paper.
-Use a rounded lathe bit to machine the center groove. This cut will require you to back out after every 1/16"-1/8" and machine down the edges around where the rounded bit has cut, the out edges of the rounded bit have a harder time cutting. The tool will stop cutting at a certain point and with too much force you risk warping the piece.
-The depth of the cut was checked with a caliper
-Once the proper depth, use the same rounded bit and machine down from the two outside lines straight down to the center.
-Then eye-ball how concave the grove should be. This is why the drawing is dirty. I refer back to it constantly to make sure I have my head around how each cut affect my thickness.
Step 3: Machine Out Inner Surface
The drill cut from before was rough, so a bit which allows me to machine out the insides of surfaces was used to take down the inside surface about 1/32" of an inch.
Step 4: Cut Taper and Shallow Grooves on Outer Surface
-To taper the walls of the shot, a taper angle of 1 degree was used.
-once tapered enough, sand, sand, sand.
-Then use a sharp pointy bit to cut in the shallow grooves to make it kind of fancy. I was originally going to knurl these but since I decided to take so much of the wall off, knurling would have been a bad idea.
The depths of these shallow grooves were just eye-balled, but as you can see in the first picture, not very deep at all. Somewhere between 1/32" - 1/64", probably closer to the latter.
Once one side is done, and you double check to make sure, then you can remove it from the chuck. It will never go back in the chuck the way it originally was, so always do as much work with one chucking to maintain a precise center-line.
Step 5: Now for the Other Side
Repeat the process with this side, but unfortunately this is one of the most difficult parts. The reason is, the taper is difficult to chuck and the piece will have a very difficult time aligning with the original center-line. To combat this, hold the end of the piece you are going to cut over something else that is tapered which slides into the traveling piece of the lathe opposite of the chuck. I forgot the name of the piece, but usually there is a pointed cone piece which is meant to help support the other end of something being cut.
By inserting the end of the piece to be cut onto something tapered, we can align the center of the piece with the center line between the lathe ends. Then slowly chuck in the tapered end of the piece (be sure that the chuck grabs onto the edge of the taper and not somewhere in the middle). Once the chuck has a firm hold on the piece, the other lathe end can be slid out of the way to allow you to make the taper cut.
Blue tape was wrapped around the taper to compensate . . .well, for the taper. This is probably not necessary.
Blue dye was used to mark out where I wanted to cut the shallow grooves.
More sanding! and polishing!
Step 6: Done & Clean Up