Adding to my collection of home made tooling. This isn't something that I absolutely NEED right now, but it's a cool little project to do on the mill and lathe that I could make from what I had lying around. This is not my design, the designer is Stefan Gotteswinter and can be found and freely downloaded from his patreon site: https://www.patreon.com/posts/dti-holder-33808199 My version is based roughly on his design, though my arm is slightly out of spec as far as his design goes. Since I have a forge, I decided to forge the curved piece and the rough shape of the swivel joints. This was done using some mild steel bar that I had lying around, 12mm bar for the arc and 16mm bar for the rounded square ends. Both were forged to rough size, the arc being slightly longer so I could trim to length and the bars being slightly wider than needed so I could machine the front and back faces to the desired dimensions. I didn't get any photos of the forging process because I did it during my lunch time on a work day so was in a mad rush and trying to simultaneously smith and photograph what you're doing when you're in a hurry just never works. I did manage to burn 4 fingers on one hand trying to pick up the length of 16mm steel from the wrong end (black heat is the most dangerous heat). Anyway, the arc was forged on a holding length of bar stock, then cut off and the ends rounded over on the grinder/linisher. After this, it was put back into the forge to get a black oxide on the ground areas, then finished with beeswax while still warm. https://pic8.co/sh/nqchKN.jpg https://pic8.co/sh/eQv30z.jpg Then the arc was mounted on a custom standoff (which was just a ~2" length of 6x2 Steel beam that I milled square top and bottom), the holes for the shafts were drilled and spot faced to ensure they were parallel and on the same plane (regardless of the accuracy of the rest of the part which remains rough forged). https://pic8.co/sh/pLgVUw.jpg The swivel joints were forged on either end of a length of 16m bar and I got them roughly central so I could hold it in the 3-jaw to turn the required shafts. Initially, the joint that would hold the indicator was turned with a 10.0mm area for the M10x1.0 thread, then a relieved area followed by another 10.0mm area. This was so that I could securely hold it in the mill to drill the cross holes and mill the side flats. https://pic8.co/sh/9UMQxA.jpg https://pic8.co/sh/nG6Opl.jpg To make the swivel joints, I drilled through with a 5mm drill bit, then went back with a 10mm major diameter center drill. This creates the 60deg taper that is the locking mechanism of the joint. The plans called for the hole to be reamed, so on the first one, I drilled the initial hole to 4.5mm then attempted to ream it to 5mm. Obviously, I fucked something up because my reamer turned into shards. Perhaps 0.5mm was too much for the reamer to take off, but I don't have a 4.9mm drill bit lying around. Probably serves me right for buying a cheap ass set of reamers. Anyway, I just drilled them out to 5mm in the end. https://pic8.co/sh/eCsNV2.jpg The knobs were turned from some 22mm steel bar, with a narrow knurled rim and tapped M5x0.8 https://pic8.co/sh/7uMuRt.jpg Next, shafts were made. These were made from a random pin that I had lying around, not sure what it was, but it was HARD. I tried cutting off a dodgy end of it on the bandsaw and it just skated over the surface. So, I put it in the forge and annealed it. That helped a lot, was still hard, but able to be cut at least. This steel, whatever it was, machined very nicely and I turned down the two shafts with their 60deg tapers to match the swivel joints and M5x0.8 thread. The threads were just cut with a die, as they are just for the tightening knobs. I also made two small washers from the same steel, these were 10mm OD, 5mm ID and 2mm thick with a bevel on one edge. https://pic8.co/sh/EUEi77.jpg Next to make was the indicator clamping nut. This was made from an old brass tap shaft. For some reason I didn't take any photos while doing it (probably in a rush). But it was a reasonably simple job of turning it, knurling the outside, then drilling it out and tapping M10x1.0 (I bought a new tap for this as there was no way I was going to single point an internal thread that small, at least with my current tooling). To do the external thread, the swivel joint was mounted in the 4-jaw and dialed in to run true on the turned portion, then the thread was single point cut to as close to the shoulder as I could. The excess was then turned off so that the slot for the dovetail could be cut. This was done in the mill, using a 4mm end mill the slot was cut and widened to the minor dimension of my dial test indicator (around 5mm). Then the dovetails were filed with my new needle files. I contemplated making a miniature dovetail cutter, but the amount of effort and likelihood of failure (either making it or using it) combined with the very small size of these dovetails meant it was easier to just carefully file them. Lots of back and forth checking and I eventually had a good fit for my test indicator. https://pic8.co/sh/pFS0AJ.jpg https://pic8.co/sh/5SguRL.jpg https://pic8.co/sh/FQxSMO.jpg The shafts were permanently mounted into the arc by peening the back side with a center punch, expanding the close fit into a heavy interference fit. https://pic8.co/sh/AqTcFo.jpg Then it was just a matter of assembling everything. https://pic8.co/sh/m6aJ20.jpg Dog for scale https://pic8.co/sh/OYyaZn.jpg