Best bit for smooth 3D contours (hydrofoil wings)

I’ve been making hydrofoil wings on X-Carve. I’d like to select a bit which will yield a very smooth surface finish on the contours and yet can still do the roughing pass (don’t want to change bits). I’m using a 3/16 flat end-mill now and am left with more sanding than I’d like.

Bit recommendations?

Id use a 1/4 inch 2 flute ball end. It can hog a lot of material quite quick once your’re past the tip.



That’s awesome! Are you building a Moth or what? Cutting out foam blade halves for sailboats are on of my main reasons for getting an XC.

P.S. Don’t forget attached turbulence actually decreases drag.

I do kite-foiling. So far, I’m doing wings and wing-saddles on X-Carve. The next project is to do an aluminum fuselage.

@MattWheeler That’s very cool! Lived in SF Bay Area for a few yeas, so got to see a lot of cool stuff. At least I was close. Now that I’m up in Seattle, I see a lot of cool stuff that they run down to the Gorge for.

While teaching sailing off Alameda, I actually responded to a distress call on VHF16 one day, it was for a dad/son team trying to get their kite boat flying. Very freaking cool.

I’m actually in the aluminum boat building industry and our next phase is to expand into airplane parts.

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Have you (@MidnightMaker) been cutting aluminum on the X-Carve. I want to. Seems like I’m chicken to try it. I just need to go for it I guess…

I cut alum with carbide 3 flute upcut bits, 1000mm/m, 0.25mm DOC, cuts like butter.

Thanks! That gives me a starting point.

What diameter bit? Spindle speed?

Ball-nose end mills are designed exactly for this purpose: cutting smoothly contoured parts. A 1/4" diameter 2-flute ball nose end mill cutter will do wonders… You should be able to do your roughing passes and your finishing pass with that just fine, and if you keep your DOC very tiny on the finishing pass then you should have zero sanding to do afterwards. Good luck!

Dewalt speed 1, 16k, 1/4"

You might get better results with a 2 flute for cutting out parts. With a three flute you’d better move pretty quick. I am just getting started as well and got a lot of advice from the aluminum pros on this forum. If you search you will see some amazing stuff.

I agree with @christianhinz. Here is a great explanation of step over, bit size, etc.

@MattWheeler Not yet, but it’s way up there on my list. The key to aluminum is to do the stiffening mod first if you have the XC1000, get your rails protected from the chips, the correct fluted bit(s) and go for it. I’m planning on starting with engraving, then move on to cutting with custom tabs. Bonus, we’ve got tons of aluminum sheet scrap laying around. :sunglasses:

Yes, the more flutes you have the faster your IPM should be, proportionately, to compensate. A lot of the problems people have with the X-Carve is that the spindle is too fast for their feed rate, so they quickly dull their bits and experience all of the problems that go along with that (chatter, wandering cuts, etc). For most situations (ie: cutters > 1/16" diameter) you should be using two-flute or single-flute cutters, most especially with the Dewalt DNP611 spindle, being that it bottoms out at 16000RPM, which is particularly high even in the world of professional precision machining.

The reason that its tempting to spin too fast is that it reduces the lateral load on the spindle and the tendency to chatter, at least until the bit dulls.

Is there a way to tell if a bit is dull by inspecting it? Perhaps with magnification?

Yes it should be fairly easy to distinguish a dull cutting edge, especially if you can do a side-by-side comparison with a fresh end mill. Also, one way to quickly tell if you’re dulling your tool with too slow of a feed rate (or, inversely, too high of a spindle RPM) is by touching the tool when a job finishes. It should not be hot, but instead should be only warm. The goal is evacuating the heat from the cutting area in the chips themselves, which can’t happen quickly enough if you’re not producing enough chips with a good feed/speed ratio.