[pickled]

I have worked with some exotic materials and composites in the past, but I don't want to just cowboy up on this carbon fiber job. I essentially have to drill a number of "aesthetically pleasing" 3/8" holes in 0.060" wall thickness 1.35" OD Carbon fiber tubing. The placement is important, but the ovality tolerance is as wide as a barn door. I essentially don't want to have a bunch of loose fibers, delamination and/or crush areas in this part so I am welcome to any recommendations that any of you may have as far as:

1.) Approach- Pilot, Drill, Ream vs. spot and helical with a carbide end mill.
2.) Tooling- I'm assuming carbide drills/end-mills are "where it's at"? What geometry works best? Coatings?
3.) Speeds and feeds- obviously related to the approach from number 1 above, but again I have never worked with this type of composite tubing before.
4.) To cool or not to cool? I have flood and FogBuster available.
5.) Fixturing? I was thinking that my vise V-jaw would work fine, but are there any boogeymen that I need to be aware of there?
6.) Machine? I can use the 1100, 770 or some "gooder" manual drill presses to get this job done.

FYI- Total volume is 20 tubes with 2 holes precisely placed in each. Note that the holes don't go through both sides of the tube...it is an interesting design.

I can manage the dust issues and health and safety stuff so I am not concerned about that. Thanks, in advance, for your thoughtful suggestions!

Doug P.

[mountaindew]

I mill thin wall acrylic tubing and find a backing material on inside of tube helps operations come out cleaner. I make them from wood , plastic or aluminum and size anywhere from just the work area to entire length of tube depending on need for extra support and fixtures or just a slip fit backer in one area. If your real industrious a 2 piece expanding plug can made that grips the inside of the tube and backs the material for drilling or other ops.
Some ideas anyway.

[JimsMachining]

we did some carbon fiber parts at work a few weeks ago, ended up using a rougher instead of a cutter, when we looked up on what cutters to use people seemed to be using diamond engraving bits. but we didn't have time to get one in. we ran a 10mm dia cutter at 7000rpmsbut cant recall surface speed (not on a tormach) but we only did side cuts not plunge or holes... hope this helps.

just looked up the cutters they were called "Corn Cutters"

[pickled]

Thanks you guys! The info definitely helps. I was thinking of backing like MD suggested, then pilot drilling with a spot drill and finally using a 1/4" 3 flute cobalt rougher to helical out to the final diameter. From what I read the diamond tools do give you excellent tool life in carbon fiber, but for this job I don't believe that I would need to go to that extreme. JimsMachining do you remember if you had any significant stringers, or were the cuts pretty clean? Thanks again gentlemen!

[MikeC8]

For thin material, you might want to try straight flute drill bits, so you do not pull on the fibres.