My my, long time no see x-carve community! I haven’t posted on here in a long time 
Time to change that!
So, I have a large flat 1/2 inch plate of aluminum I cast myself, it is comprised of a few different grades, but I think most of the mass is mic-6 toolplate offcuts. I need to surface mill the rough cast finish, what bit should I use? I was thinking about a fly cutter, but they don’t seem to have 1/4 inch shanks. Recommendations? Also, since I’m trying to surface mill aluminum scrap, it needs to be as cheap as possible.
Do you know what other alloy might be mixed in?
I’ll give you my advice on bits and you can do with it as you may. You should never run anything unbalanced in a high speed router. It’s unsafe to the operator and not good for the router. A fly cutter is a bad idea in a router.
You should be able to find a recommended rpm range for any tool from the manufacturer.
A 3/4" straight cut bit is probably your best option.
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If you ever want to figure out how fast something will be flying at your face if it comes apart:
Circumference of the bit x rpm = number of inches the outside of the bit travels in a minute
multiply by 60 to get inches per hour
1 mph is around 63,000
So, take a 1 1/4" fly cutter: circ is approx 4’ and on the Dewalt speed 1 is 64,000 ipm x 60 = 3,840,000
divide by 63,000 = metal flying into your face at about 60 mph
Thanks for the info, what about the micro fly cutter BillBlades presented? It seems to be designed for high speed cnc routers, but I will probably just use a large bit I already have, since they want 20$ for it.
The mass is probably 70% Mic-6, 20% A356, and maybe 5-10% soda cans, so there is a good amount of magnesium.
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Fly cutters aren’t designed for high speed routers. Micro Mark is a company that specializes in tools for model makers. They have a miniature vertical mill that they sell. Verticals mills run at much lower rpms and are built to handle the side forces in milling.
Your slab likely has a lot of slag and impurities in it. Use a cheap bit.
If you really need it, take it to a machine shop with a nice big vertical mill and ask them to surface it.
If it were me, I wouldn’t put that on my X-Carve. Just my 2 cents, though.
Oh ok, I see. I will probably just use my biggest straight bit then, also, it’s pretty pure, there is a lot of oxide on the surface since I had to let it air cool, but it was treated with borax and skimmed and then baked in the furnace.
Well, it’s been a good long while since I gave this thread any thought and today I figured I would just throw this block at my x-carve with a yonico carbide 1\4 inch bit since I figured, eh, my machine is tough, might as well try it! And to my surprise, it went perfectly! I intended to set the DOC fairly conservatively, and didn’t realize it was cutting so deep, but to my chagrin the machine didn’t even flinch cutting somewere around 1\8 inch DOC. AMAZING!
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Also, what kind of mods does your x-carve have?
Feed rate was 23 in/min and I used a Yonico 31214-SC Carbide 1\4 spiral upcut end mill. :3
It’s pretty beefed up, 175 oz nema 23’s, Makita router, steel bar y-brace and my acrylic dust shoe.
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speed setting 2, which according to the manual is 12,000
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You should have no issues whatsoever! lower rpms seem to be the key with aluminium, or higher travel speeds, otherwise it gets all gooey 
Honestly, apart from a little chatter on the corners my x-carve didn’t even notice the aluminium at 1\8 DOC and 23 ipm, so you could probably triple the travel speed for higher rpms. Actually, aluminium and plexi seem to both want similar speeds and feeds. Plex will get really gooey if you don’t cut fast, I cut plex at 75 ipm and I usually even do flood cooling with water too.
You need a certain "chip thickness / slice thickness per flute, otherwise it will rub and heat up / alu get gooey.
Lower number flutes usually provide better chip clearing/removal which also help. Lower rpm/single flute is generally the better game for alu.
A stiffened X-carve, especially the smaller version, is surprisingly crazy rigid. When I was cutting at 0.125 DOF, I only had minor chatter at the direction change, It’s a tough machine.
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