Dragonfly: Part 2. Setup
Now that the patterns are made and loaded into the Brocade Engine the real work begins. A little bit on brocade engines as they are a little controversial. Some people lump brocade engines into Guilloche' equipment (ex: Martin Matthews in his book on Engine Turning) and some people do not (ex: Calina Shevlin in her book on Guilloche'). There are some big differences between the two (from the viewpoint of the artist - not machine design or mechanical differences).
First, the cutter on Rose Engines and Straight Line Engines, once engaged in the work piece move left and right while and engrave one long line. Brocade Engines have a cutter that moves in and out of the piece and do a lot of pecking. So, cutter moving left to right and back again vs. in and out. And, the Brocade Engine also has a set of rosettes to create the stippled background pattern - but the cutter is still moving in and out, not side to side.
Second, the set up is very different. Rose Engines and Straight Line Engines have a relatively short setup time. For the most part, you determine the cutter to be used, the depth of cut, the pattern to use (Rosette or Pattern Bar) and which Rubber (follows the pattern) to be used. Adjust the distance the sliderest travels between each cut and get to work. Of course, every new line to engrave takes at least one new adjustment to the equipment - and sometimes several adjustments to the machine. This is a very time intensive art that requires a lot of concentration and keeping track of where you are in the pattern.
Brocade engines are very different. One hundred years ago a workshop would have several or 20 workers running rose engines but only 1 person that could effectively set them up. Brocade engines, too, follow a pattern but the patterns tend to depict an image or design rather than a single path to follow (like Rose & Straight Line machines). So, there is more work up front in the pattern(s). And, setup is a lot more difficult - not so much for a single pattern design but for dual pattern designs it can get very.... well, fiddly.
Yes, I really did use the word "fiddly," and I will use my machine as an example. I put in the patterns, chuck up some metal - usually copper for setups - and then start 'er up to see what I get. Typically it comes out as junk, at first, and will take a number of tries to get it just right.
Here is the first (and second - because I brocade over the top of the first try) try at the image. The pattern is being cut too deep for the effect I want. This can be seen on the engraved image but also from the size and behavior of the chip coming off the cutter. Additionally, the background pattern is not being seen, yet.
I start to being the background pattern in and fines the foreground. I also noted that the cutter needs to be sharpened so I did take it out and sharpen. Typically, I hone to about 14,000 grit so the cutter is like a mirror. The outer ring is when I determine I needed to sharpen the cutter. You can see on the inner ring that cut is much better and the background pattern shown up much better. Part of this is the sharp cutter, part is because I am fiddling with the depth of cut at the cutter and the depths of cut controlled by the two patterns and the rosette. Now I will explain why I use the word fiddly...
On my machine in it's current configuration (lots and LOTS of adjustments on Brocade Engines!!!) the 3 different follows (2 for patterns and 1 for rosettes) I have 32 pitch screws. Therefore 1 revolution is about .162" of movement of the follower screw. Haven taken some (relatively) rough measurements, a 5 degree rotation of the Follower gives me a movement of about .00225". This motion, reduced in linkage to the cutter, adjust the depth of cut by .000333". This seems like, with this fine of adjustment, it would be easy to dial in depths of cut. But, from much experience, I can tell you that, when getting a pattern honed in - a 5 degree rotation of an adjustment screw can make a HUGE difference and dialing in can require lots of 1 degree and 1/2 degree rotations - adjusting 3 different screws to get things just right. Yep.... fiddly.