I wasn't much work at the shop today, so I got the opportunity to work on my Duif Workholding project!
Spent the day making the baseplate for the dovetail vice, and it turned out amazing!
I used round stock to make the main plate instead of square stock because of how it's made at the foundry. Square stock is typically poured into a mold where round stock is rolled into its shape. The benefit of using round stock is that because it's rolled, the center point of strength starts from the middle and moves outward, making a uniform shape to the edges. Whereas square stock doesn't have a defined strength point and is kind of all over the place when it's cast. The differences are minimal for what I'm working on, but it's a fascinating idea to keep in the back of my head when working on more strength intensive projects.
To surface the material, I decided to use a 3" fly mill (a fly mill is a large cutter with inserts that cut the metal) to deck the top of the stock, ensuring I had a perfectly flat surface to work off of. However, what I didn't take into account was that since the stock was only 4.5" in diameter, the size of the tool grabbing the aluminum was a significant ratio of the part; what could have happened was when the fly mill entered into it's cut if it were enough of a bite it would yank it out of the jaws and throw it across the machine. Thankfully I only took very light stepdowns, and so wasn't an issue, but my boss pointed out that using a smaller ratio endmill would reduce the chance of that happening even though it would add to the overall run time.
I accidentally broke a 1/4" endmill when I came into the stock's side too quickly, which unfortunately left a mark on the finished product. I was using the same endmill to finish off the tall walls of the clamp piece I made the other day and didn't think it necessary to swap it out with a stubby flute one because the flutes extended for about an inch the strength was significantly reduced at the tip.
For the large facets on the plate's sides, I used a 1/2" ball endmill to finish the surfaces. However, since I roughed the area out with a square endmill, there were pretty large steps it had to mill out as it was finishing the surface and the load of the tool deflected it ever so slightly, which left small dent looking marks where the tool jumped around. The solution for this is to rough it out with the same ball endmill, but leaving a tiny layer on the faces, just a whisper of a cut (no more than two thou), and come in again a second time to finish it up. In this fashion, the tool would have almost no resistance and so leave a much better finish.
When cutting the dovetails in the main groove, I found that if you leave more than three or four thou on the face that the dovetail cutter is passing through, it will make this gnarly looking chip. It doesn't affect the finished product, but it's fascinating to see on a CNC mill.
I used a set of soft jaws to hold the raw stock in place, and after finishing the first operation, I was able to cut the jaws again to match the facets on the side of the piece. From the other side, I could remove that little bit of material I used to hold onto and get the final details finished up, which in this case was just a small step down in the center of the disk that would fit onto the raised cylinder on the Pocket NC.
For kicks, I decided to add my Duif Workholding logo to the plate's top surface using an engraving bit. I could program this quickly by converting the image to an SVG file using an online converter and importing that directly into my design, thus giving me geometry to reference when setting up the engraving toolpath.