![]() ![]() In the typical flush riveted metal project most of the rivets used will be either 3/32" (AN426-3) or 1/8" (AN426-4) in diameter. Small drill sizes are very difficult to judge by eye, so use a metal drill gauge to remove all doubt. Drill the holes through the tape - then remove the tape.ĭon’t leave the masking tape on more than a day or so because it becomes increasingly difficult to remove with the passage of time.īut why use the tape in the first place? Well, the tape protects the metal from drill scratches and helps prevent the drill from walking.Ĭhoosing the correct size bit for the hole to be drilled is extremely important. Instead, draw and mark the hole locations on the tape. Lay masking tape over the route where your rivet layout and spacing is to be drawn on the aluminum skins. Here’s a useful tip passed on from builder to builder. When this happens, the drill will leave an ugly scarred trail across that nice smooth metal surface. Ignore this technique and you will risk the chance that your drill will take a walk and scoot off the marked hole location. This will almost guarantee that the drill bit will stay accurately seated in the punch mark. Hold the drill perpendicular to the surface, exert a little pressure, and turn the drill chuck by hand a little before pulling the trigger. ![]() Use a center punch and a light hammer tap to pinpoint and slightly emboss the marked location for every important hole.īetter still, use an automatic center punch to pinpoint every rivet location.Īn automatic center punch is much easier to use and you may find it to be more accurate for your own use.Īlthough a punch mark indentation helps ensure that the drill will not stray off the mark, you can help, too. It is permissible to alter the hole spacing slightly to avoid such problem traps. Before you mark a rivet location, assure yourself that there is no obstruction (or flute) in the underlying frame where you intend to drill a rivet hole. When a line of rivet holes is to be drilled, a centerline is normally drawn first and then short cross marks are made to establish each hole’s location. Expect this and count on resharpening or replacing the dulled bits before using them again in aluminum. a desperate need for some sort of an angle drill will arise from time to time.Įven though you are building a metal airplane, you may have to drill holes through fiberglass fairings, cowlings, and other component parts.ĭrilling holes through fiberglass dulls drills quickly. It is in a situation like this that a right angle drill becomes necessary for making those almost inaccessible areas accessible. Even with a short bit installed, this means you will need approximately 10" to 12". In addition, access to the area where the hole is to be drilled must be accessible enough to allow you to maneuver and position the drill with the bit installed. ![]() At best, an ordinary electric drill will allow you to get within 1" of a corner but certainly no more. Your control (either air driven or electric) will very definitely have access limitations.įor example, you will find that you cannot drill closer than, maybe, 3/4" to a corner, or a perpendicular rib surface or bulkhead. I also recommend the acquisition and use of a good lightweight air drill because it is less tiring to use than the average electric drill and has an easily teased trigger for precise speed control. In addition, you should acquire a couple of 12" long (#30 and #40) drill bits for drilling in hard to reach places.īecause these long bits can be easily flexed with your fingers they can be made to drill close to corners, and just about anywhere else that a 90 degree angle drill would otherwise have to be used. However, the tougher, more expensive, Cobalt bits should be used to drill hardened steel parts like landing gear legs and engine mounts. The type of drill bit you will probably use the most is the High Speed Drill (jobbers length) because of its ready availability and low initial cost. Read on to see how you can avoid or at least limit your encounters with these, all too common, hole preparation problems. Making machine countersunk holes for flush rivets (where needed) too shallow or too deep.Forgetting to dimple the top and/or bottom skin for flush riveting.Forgetting to deburr the holes in both skins.However, as if all that isn’t bad enough - after the hole is drilled you can still create other problems by: Drilled O.K., but only after scratching the skin.After all, with thousands of holes to be drilled in a typical all-metal aircraft project, the "opportunity" exists for some of those holes to be: However, not everyone can drill a nice round hole - in thin metal - where it needs to be - and do it right every time. ![]()
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