Engraving on a Mini Mill

[Dub_James]

Thinking on getting a Mini Mill, but can't seem to find any information on how to engrave with it. Most engraving links on the net seem to refer to homemade CNCs for engraving plastics and soft metals.

Anyone know what cutting tools would fit an R8 collet or end mill holder?

[Darrell]

What are you wanting to engrave? Design, that is? You mentioned plastics and soft metals as substrates. McClarkus uses a CNC router, and does some really neat stuff with it:

http://phantomcanyoncarving.com/index.htm

Maybe he'll chime in.

We do engraving at work, using either scratch and drag high speed engravers, or CO2 and Nd YAG lasers. I did a lot of testing on the lasers recently, imaging and materials testing for possible new products. Had fun (mostly) and learned a lot.

[McClarkus]

I know nothing about engraving on a mini mill. I would think you may be limited to geometric designs because doing a smooth curve would be tedious and difficult without the CNC capability. I use little carbide engraving bits like these for doing lettering in metals like my dog’s tag.

http://www.ebay.com/sch/i.html?_trksid= ... &_from=R40

If I size up these little 1/8” bits to ½” I can use the CNC to “Vee” carve wood, high density urethanes and other softer materials. Those can then be combined with the 3 dimensional artwork to do some interesting things. I’m assuming you could get a lot of money into a mill rather quickly. You may want to explore some of the home oriented CNC’s if you have a couple thousand to play with. You may find them to be a bit more versatile. Never having had a mill I also have no doubt that they can do things that my CNC cannot. Another drawback to the CNC is the rather abrupt learning curve. I have destroyed a lot of material, and broken a lot of tool bits through my own foolishness, but I’m getting better.

[Dub_James]

Probably brass, alum, steels, some hardened. Most likely first task would be engraving on AR 80% lowers, eventually AK receivers. I'll likely CNC the mill in the near future, but I really want to have the tooling side sussed before I get to that stage.

McClarkus - I've seen those kinds of engravers online, but are they what needs to be used in a milling machine, as opposed to a homemade "CNC machine" used for engraving plastics, wood, etc?

[McClarkus]

Those little bitty ones are really delicate. They are like sharpened needles. I got some that were made by Kyocera for the electronics industry to engrave circuit boards and they worked great for me in brass. You just can’t push them very hard or they break. If I were going to engrave the side of an AR lower I would go with a 60 degree ¼” Vee bit because they are pointed enough, and a hell of a lot stronger. I get some of mine from a company in Wisconsin called Vortex. They are not cheap but I really like their vee bits because they are sharpened all the way to the very tip. I’ve had others from different companies that leave a very small flat spot on the end from their sharpening techniques. That’s fine if I’m carving a recess with a predetermined flat depth but not if you want precise lettering. Some carbide is finer grained than others but I think most would work ok in either setup but again, I am not a milling machinist.

[HTRN]

For fine lines in hard metals, you use what's called a drag engraver. It's basically a needle sharp point that you drag around on the surface of the metal. The spindle generally isn't turning. The downside to them is that the lines can be too fine, and thus hard to see.

My preferred engraving cutter is one with a decent sized flat on the end, and a fairly steep taper(IE pointier). The idea is to have a flat large enough that makes it stronger, yet small enough that that it makes a sharp line for finer print. Probably something between .020 and .050. The sharp taper is because if makes the cutter less sensitive to depth adjustments, especially if what you're cutting isn't perfectly flat, it makes it look fairly even. Do keep in mind, that if you do use them, they like really high RPMS, so adding a home brew auxiliary high speed spindle might be a good idea.

Finding both is fairly easy. Bits&Bits sells engraving cutters and drag engravers(not the body for the spring loaded types unfortunately). Tormach sells a complete springloaded Diamond drag engraver for around 70 bucks.