Some good progress on my chapter ring trial run.
I found a scrap of 1/16” mystery aluminum (some stuff I’d salvaged out of the garbage pile in our lab back in the days when I worked!) This stuff doesn’t seem like 6061. It machines a little differently than 6061 usually does. But it will work for my test.
Anyway, I took the piece as it was, with the weird shape and a few extra holes in it, drilled a hole to represent the center of my clock face, and set it up on the RT, with that hole centered. I made a cut about halfway through the piece with a 1/8” end mill to mark the outer and inner diameters of the chapter ring.
Then I moved to the 1/32” end mill that I’ll be using for the engraving task and cut radii for the inside and outside of the chapter marks. I’ve just completed that task here. Unfortunately, it’s a little hard to see the grooves against the color of the aluminum in general.
To help make things easier to see, I covered the area I was working with one of those fat Shapies that I often use because it’s easier than breaking out the Dykem. That really helped.
Then I cut the wider chapter marks between those rings, followed by the minute marks between them. Here I’m a little more than halfway done cutting the minute marks on my test chapter ring.
One of the test numerals I’m doing is the VIII, because it is the widest one. I wanted to make sure it fit without cutting into the other things on the face. Before I started cutting, I could tell that it would break through into the minute mark ring. So, to prevent that, I modified my spreadsheet to make the numerals just a tad shorter. This wasn’t very hard because I’d made ‘numeral height’ a variable in my sheet (along with the various widths and serif size, etc.) So I changed it from 1/2" to 7/16”. I’m using a 1/32” end mill to make the marks, so they will extend 1/64” above and below the dimensions specified in my spreadsheet. So they’ll really be 15/32” tall, so not too much of a sacrifice.
After this first revision to my spreadsheet (well, OK, the 1537th revision
), I went to cut my first number. I started with the serifs. I designed it so that the serif’s of adjacent numerals would connect. And my Vs don't have a serif along the bottom (I found examples of both, with and without serifs, so I just picked a way to go). That's why there are two serifs at the top, and only one along the bottom.
Next, I rotated the table, offset in X and Y as specified, and cut the narrow diagonal line for the V.
Then I cut the wide diagonal by rotating the RT the opposite direction, offsetting in the opposite direction, and making multiple cuts. I tried 3, as I have shown it in my spreadsheet, but that didn’t quite do it. My plan was to just ‘wing it’ to empty out the rest of the area by hand, but after doing this one, I think I’m going to modify the spreadsheet to walk me through this. So another revision of the spreadsheet is coming.
Finally, I moved the RT back to the ‘central’ position and engraved the three wide uprights for the I’s. Again, I ended up doing more passes than the three shown on the spreadsheet. I think add a few more lines here too, while I’m at it.
Next on my trial run of the chapter ring, I was going to cut the 12 (XII) since this is the next widest number. And I wanted to do a test run of an X. However, as it turns out, I was looking at the coordinates for the serifs to see how long to make the joined serif, and I realized that my XII has an error in the spacing between the X and the first I.
Look at this and see if you notice it too. The spacing is closer than in the XI or the IX.
I see it clearly now, but obviously hadn’t noticed it before. So that’s another thing to fix. (The list is getting long!)
Also, the serifs between the I and the X in the 9 (IX) don’t join like they are supposed to. Nor at the top of the XI. So I’m going to have to figure that one out, too. I think the only reason the serifs join in the XII is that the spacing between the X and the I is wrong. I think it’s off by a half an I-width, but I’m not sure. I’ll have to debug that.
So, LOTS of spreadsheet debugging going on. But a good test run too! I’m glad I did the test before launching into the actual chapter ring!
I am quite pleased with how the VIII turned out. All my calculated values and angles seemed to line up quite well. So that part of the spreadsheet test passed with flying colors. Now I only have to fix all those other little nits.
Oh yeah, another part of this test is to see if engraving the numerals 10 thou deep will be enough. It seems that I can do a 10 thou pass with the 1/32" bit easily enough. If I have to go deeper, I'm afraid I'll have to start doing multiple passes. Not only will that take longer, it will double (or triple!) my opportunity for mistakes. So I'm hoping that 10 thou will be plenty
Kim
