One off CNC request

Trying to cut a one off part out of aluminum. I first made it out of thin plywood no issues, moving on to a 3/8" aluminum.
Well I have now ruined two #201Z end mills, possibly my Shapeoko and the core material; I am admitting defeat that aluminum may just be past my capability.

Anyone willing to cut this piece for me for a reasonable fee?


aluminum.c2d (80 KB)

You are making this cut in the most difficult possible way:

cutting slots and drill points as narrow as the tool.

Assign pocket toolpaths to cut down to tab height.

Using a smaller tool, ideally one w/ single flutes will also help since it reduces the amount of material being removed.

The other question is which alloy of aluminum were you trying to cut?


Are those end mills really ruined? When I started with aluminum, I had some really bad looking end mills cause by aluminum welding to them. If that’s what you have, you can actually clean them fairly easily with lye. Winston Moy had a video on doing so.


Also, contact us at if you haven’t about your machine and we’ll do our best to get you up and running again.


Darn it! I forgot to pick up a bag of Doritos when I was at the store.

Always cool to see some dorito action.

Where are you located @mccdeuce ?
That looks like an aircraft setup, an ultralight perhaps?

So I do appreciate that I have much to learn still but I am not fully tracking.

  1. The drill points are just pecks that mark the locations for me to go in with a drill press and drill the actual points.
  2. Why do pocket tool path when I need to whole section gone? Doesn’t that just cause more cutting iterations of the material?
  3. Originally planned for a single flute ZrN, #278, but had heard differing views on 1 vs 2 and the #201Z lists flat cutting aluminum as one of its capabilities. Guess I should have stuck with my original plan based on your recommendation or gone with a .125 cutter.
  4. The alloy was 6061 AL, 3/8" thick.
  1. Okay, but w/ a smaller tool it should have worked to machine that.
  2. To reduce tooling engagement
  3. The #278Z was a good idea — that said, the #201Z would have worked fine if you weren’t milling a slot
  4. That alloy should cut fine — the thickness of the material is why a slot was such a problem.

Will have to see when I build the courage to go look at my bits and my machine again. Potentially they could be refurbished. The Z-Axis looks like it to a twist off and is probably repairable with some easy replacement V-wheels.

@MikeG this is a for a Glasair S2S airplane that I am building. I am modifying a Mazda 13B rotary engine. This part I am trying to build is a intake manifold plate that I will weld the pipes onto.

Overall update: I was able to salvage the part and finish the cut by drilling run points with a drill press and finally cutting the part out with a bandsaw and grinding sanding to a decent quality.


  1. Copy. I was always under the impression to not use mills for drilling action. Will read up some more.
    The portion that I failed on was cutting the part out of the stock along the upper section. The 2 large holes, 2 ovals and 60% of the cut out machined perfectly. What you are suggesting is the curvature of the upper slot combined with the depth were the issue. The forces of being a deep slot on the #201 were the problem.

Appreciate the lesson.

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I would actually put the correct size drill bit (or a pilot bit) in a collet on your router. Of course an ER collet spindle would be best. But you could still use a 1/8" or 1/4" (depending on your router collets) drill bit for marking center of holes. If you have to plunge with an end mill, slow is good and a spiral is better than straight down in some cases.

Also rather than a full pocket (yes, way more work when you need a thru cut) I would do a stepped cut. IE set your depth to maybe 1/3 or 1/4 of the stock (maybe even thinner, I haven’t worked with AL myself) and then take a pass, set the depth a little farther down, take the next pass, etc until you are thru the material. That is what I do on some stones (granite or marble) on our big CNC machine at work. Plenty of differences between wood, stone & AL, but generally a good process will work on any of them. Depending on what I’m doing (and the tool being used) I have taken up to 6 steps to get thru a piece or down to desired thickness when not going completely thru.

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