I presume your intent is to drill accurate, round perpendicular holes in thin materials like body tubes. This is a task that is harder than it looks as the material (cardboard, phenolic, Quantum tube, Blue Tube, or fiberglass) is very thin and subject to deformation and tearing (in the case of cardboard or blue tube).
Your options are four: a laser cutter, a special punch, a mill, and drilling. Most of us can’t afford a laser cutter or a special punch, both of which are better suited to assembly line mass production. A mill will work great, except on friable material like cardboard or blue tube. The best option for most of us is to drill the holes by hand or with a drill press.
The first order of business is to mark the exact center of the hole to be drilled. If you are trying to drill multiple holes around the circumference of your tube, I find it best to lay out the hole positions on a sheet of paper that wraps around the tube, sort of like a fin guide but with cross marks where you want the holes to be. I transfer the hole positions with a Starrett scribe, which is super pointy and won’t deflect like a straight pin. All you need is a very tiny dimple. Do not use a center punch else you risk crushing the tube.
Next, you need to get your material to be drilled dead perpendicular to your drill. This will require a V-block aligned perpendicular and concentric with the drill chuck. I use this tool to center the V-block:
Router bit centering pin.
As an alternative to a V-block you can use various jigs that have bushings or drill guides with the “V” integral to the device. These can be used free hand if you don’t have a drill press. I find the
Plastic drill guide a bit sloppy, the
Big Gator Drill Guide less so.
Dog House Rocketry (Binder Design) used to make a metal jig with interchangeable bushings. It was great but is no longer in production.
Next is your choice of drill bit. I agree a 135 degree split point bit is probably best for hard material. Regrinding the tip is not for the faint of heart though, and can be a challenge if you are trying to do this on a 1/8” bit. Alternatives include a Black & Decker BulletPoint™ bit, which drills its own pilot hole. For cardboard and other fragile materials I use a brad point bit. The very pointy tip aligns perfectly with the prick mark made with the Starrett scribe and the cutter wings score the outer rim of the hole without tearing, though you have to feed slow. Don’t use those cheap Chinese or Fischer brad points. Get high quality ones from Fuller, Rockler or Lee Valley Tools.
If you are going to drill your hole without using a bushing, consider using the shortest bit possible.
Machinist’s Center Drills are very stiff and short but their tips are made for drilling metal and will not make a neat hole in cardboard. If you are using brad point bits, you’ll be stuck with what you get.
The tube to be drilled should be supported on the inside so that the pressure of the drilling operation does not deform the tube or cause blow-out at the back exit of the hole. Use a heavy coupler or a piece of turned material that can be slipped inside the body tube for support.
Finally, use an appropriate RPM on your drill press. For most of the material used in rocketry, use the "softwood" setting from a speed guide like this:
https://images.meredith.com/wood/images/pdf/speedchart.pdf. Advance the quill slowly, especially with cardboard, so as to prevent tear-out. And practice on a piece of scrap first.
Oh, and that laser? Fuhgeddaboudit. It’s not accurate enough, it takes too much fiddling and the illumination is too intense to see the subtle pencil or prick marks you are trying to center on.
Hope this helps.
Anyhow, I bought a MAC Performance 3" Black Fly kit and am doing some homework preparing for the build. I haven't found a thread specifically addressing equipment and techniques used for drilling perfect holes, so I'd like to ask those experienced here. I assume that I'll need to invest in some sort of desktop drill press, and that I'll build larger rockets in the future (up to 6"?). I would greatly appreciate feedback on any critical specifications such as: spindle to table length, spindle travel, table size, fixtures like table vice, etc. Any recommendations on specific models would be great too.
