Drag Engraving on the Nomad 883
Winston Moy has a great intro to drag engraving on his YouTube channel here: https://youtu.be/bIp1zSIck9M which is how I found out about this in the first place. So this won't be a tutorial per say, but will cover some of the trials and tribulations I went through to get everything working, as well as some essential details and tips.
Drag engraving itself is a very simple process, you have a sharp tool that you drag across the surface to create a uniform scratch on it. This tool can be a diamond tipped tool or a solid carbide one, so naturally I started with the diamond tip as they are harder and can scratch anything.
Here's what I bought:
Spare Diamond Tip:
(Note, all my testing has been done on stainless steel)
And it really can scratch anything, I was scratching everything with it. Setting it up in the Nomad 883 mill can be a little tricky though, as you can't use the tool height sensor with a diamond tip. My workaround was to make an aluminum rod the same length as the drag engraver, (minus 1/8" for my desired compression), that I could use to measure initial tool length and to set my zeros. I would bottom them out in the collet to ensure the same tool height. Then I modified my CAM code to not perform a tool measurment upon startup.
But I quickly learned how fragile the tips are. It was totally my fault, I ran the engraver off the edge of the part and (the engraver being spring loaded) it jammed the tip into the fixture below, shattering the diamond. I thought it could handle some impact, but it really doesn't at all.
I broke two more tips after that. If I would have stuck to outlining, I don't think I would have broken any more, but I've been using cross hatching to fill in my engravings, but I learned a lot.
If you stick to a parallel crosshatch, you get a very reflective engraving that shines nice in the light. If you do another 90° perpendicular pass, it creates a much more dull engrave, almost like a sandblast finish. I've been using the second one.
The problem I found in that is that there can be a fair amount of chatter when performing the perpendicular pass. This is how the other diamond tips broke, they just couldn't handle the vibrations and shattered.
So I tried a carbide tip after that discovery. I went with a 120° tip with a Ø1/8" shank, so I could adapt it to my existing spring barrel. I had to make a custom bushing to glue onto the carbide end so it wouldn't fall out, but everything else about it is fine. It is nearly three times as long as the diamond tips, but that doesn't seem to matter, as I didn't notice any extra flex in the tool while under load.
The carbide tool has performed excellent! It still chatters quite a bit during the infill, but there seems to be little signs of excessive wear in the tip. I don't think I'm going to go back to diamond, as I see little benefit that outweighs the cons.
Here's a summary of the things I've learned in this process, through research and experimentation.
Tips for choosing your tips:
► The tip angle determines how fine of a cut you make, 60° is very fine, 120° is wider.
► The tip angle is proportional to tool wear, 60° will wear out faster than 120°.
► The Nomad 883 mill uses electric conductivity to determine tool length, so you will have to come up with a work around if you use a diamond tip.
► A lot of drag engravers come with a Ø1/4" shank, so you can't use the default collet with the Nomad 883.
► Diamond tips can theoretically mark more materials than carbide can, but carbide is way more robust.
► Diamond tips can't handle cross hatching infill as well as carbide ones can.
I hope this helps someone down the road! Go forth and happy engraving!