What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Drilling Pre-Punched Holes

R

RV701775

Active Member
Does any one have any suggestions on preventing misalignment of holes when match drilling pre-punched components? I have found that even when I cleco every other hole, sometimes the holes that I am drilling may be misaligned slightly, resulting in a slightly oblong hole on the bottom that is out of the mil-spec diameters.

One example was when drilling the reinforcing bars into the rear spar of the HS. I have tried both reaming and drilling with my 3000 rpm drill. On these long components I find that I end up with at least a few holes through the thicker component that are enlarged slightly, or an oblong hole on the bottom component (i.e. thinner spar) once I flip it over.

Also there are location where it is almost impossible to secure the two components with a clamp due to the angle or a flange in the way.

Thanks!
 
If they are close enough that you can cleco the parts together, then I would expect the holes to be in alignment unless maybe you're holding the drill at an angle or the clecos aren't pulling the parts tight together?

On the aft bars of the h/s, there is a note in a plan to radius the back edge of the bars to get them to nest into the radius of the spar if necessary. Have you done that and are you sure they are laying down flat?

Edit: one more thought- don't know your experience level, so I'll just go ahead and ask; are you using the right size cleco? Silver for #40 holes, copper for #30?
 
Last edited:
Two ideas...

1. Check the run-out on the drill chuck/bit -- this is a common cause of oblong holes.

2. Play with the clocking of the clecos, 0?, 45?, 90? - and so forth. Clecos can introduce fore/aft or side/side drifting when clamping material together.

Cheers!

B
 
I love that tubing trick!

If one of your parts has a flange (like a rib) and it's not fluted enough (or fluted too aggressively or inconsistently), the holes may not line up with the prepunched skin. Make sure when you eyeball down the rivet line, there aren't any bows or waves. And don't be shy, use a cleco in every hole if the parts are being stubborn.
 
Why would run-out manifest as oblong holes vs oversized holes?

Also, is flex a problem vs run-out?

I recently tried using a sub-compact makita drill for the practice kit, and got holes that were not to my liking.

The run-out *appears* fine to me when drilling with no load, aka spinning the drill bit in the air.

However, though the whole chuck/shaft assembly deflects under load very easily vs my corded drill. could this affect hole quality? is this something other than "run-out"?
 
Some times a drill bit is sharper on one side and drills unevenly. The bits we use on our RVs are so small it is hard to check for this, I just try another drill bit. Another thing that improves hole quality is to use a reamer instead of a drill bit to enlarge prepunched holes.
 
Different brand clecos fit differently. Wedgelock, from Cleaveland, seems to fit the tightest.

Some other brands won't even hold two dimpled pieces of aluminum together - the clecos fall out.

Dave
 
I've now managed to get good holes on my end without changing drills. It seems the flexibility in the Makita sub-compact drill wasn't an issue.

- The tip of my two week old Husky automatic center punch had broken off and was rounded, leaving a bad center punch. Its mechanism also required a pretty large amount of force and tended to wander itself a bit on firing. I replaced it with a "Spring tools double ended prick punch & center punch" which seems much more controllable and accurate.

- I improved the clamping on my piece by clamping down areas I'm not working on tightly with wood.

- I start slowly and exert more vertical pressure untl I can see the hole has started, then go to low-pressure/high speed.

The results look great, and the drill hasn't wandered once.
 
You must log in or register to reply here.
Back
Top