When making the optical center punch a round part needed to be centered precisely under the mill spindle, a perfect job for the dial test indicator, if there was a good way of holding it off axis. I had nothing to manage this feat, so will make one.
The fixture will consist of two parts, a bar that will be held in the mill collet and a slide that will hold the DTI to the bar. The bar was tackled first after figuring out how best to insure the bar was centered with the stub for the collet.
A 2" length of 1/2" X 1" steel was located in the scrap bin. It was first marked and then cut into an L-shape with a hacksaw. Two faces were cleaned up in the mill, the inside of the long arm and the end of the short. The L was held in the four jaw chuck on the South Bend lathe. It was carefully centered in one direction so the short leg of the L was centered side-to-side, using a dial indicator mounted in the QCTP. The stub was reduced until it was a sliding fit in the mill's collet (0.375").
The two sides of the long leg were both milled down so they were even with the round stub just formed. This left the width of the bar at 0.371". The bottom was then milled so the total height of the bar ended at 0.375" as well after a bit of sanding. The free end was heavily chamfered with a file. The resulting bar is seen below.
A 1 1/4" X 3/4" X 1/2" scrap of brass was located in the bin to use for the slide. The two ends were cleaned up in the mill. The piece was marked for drilling the through hole and for the ensuing square hole. It was drilled in the vise up to 3/8" after beginning the hole with the spotting drill. This is shown below.
The corners were filed using a three corner file. The bar now slides easily through the slide. The slide on the bar is shown below.
The slide was returned to the milling vise and located with the edge finder. A hole was drilled for the DTI shaft up to a #22 drill, 0.156" providing a decent sliding fit. Two holes were then cross drilled and tapped 6-32, one for the bar and one for the DTI shaft. After a bit of cleanup the completed slide is shown in the first photo below. The second photo shows the fixture assembled with the DTI installed.
