What's new
Van's Air Force

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

Step Drill Hole Centering

Meat

Active Member
Patron
Hi All,

I could benefit from some collective wisdom. I'm having issues using a step drill to enlarge pilot holes from a dimpled #40 to 9/16" for comm antennas on the bottom of my RV-14 QB fuse. The holes wants to migrate off center. Does anyone have any techniques for keeping a step drill centered when enlarging from a pilot hole? I'm using lube, controlling the speed and making sure to keep the drill square to the surface. I've had this problem in the past. I've drilled one hole so far but wary of the issue I stopped at 1/2" to inspect and its migrating off center. I can clean it up with a file to final size but there's got to be better way for subsequent holes. Any advice is very appreciated. This shouldn't be hard.

Cheers,
Scott

RV-14
 
Are you enlarging the pilot hole to the same size as the first step in on your step drill bit or forcing the step drill bit through a smaller hole?
 
I was starting from the dimpled #40 that Vans had left me. Are you saying I should enlarge to 1/4" first and use step drill from there?
 
Hi All,

I could benefit from some collective wisdom. I'm having issues using a step drill to enlarge pilot holes from a dimpled #40 to 9/16" for comm antennas on the bottom of my RV-14 QB fuse. The holes wants to migrate off center. Does anyone have any techniques for keeping a step drill centered when enlarging from a pilot hole? I'm using lube, controlling the speed and making sure to keep the drill square to the surface. I've had this problem in the past. I've drilled one hole so far but wary of the issue I stopped at 1/2" to inspect and its migrating off center. I can clean it up with a file to final size but there's got to be better way for subsequent holes. Any advice is very appreciated. This shouldn't be hard.

Cheers,
Scott

RV-14

I noticed that also in thin sheet metal. It doesn’t seem to happen with thicker stuff. I assume it’s from the unibit step breaking through and shifting over when it does. Try pushing very light so the step goes through most of the sheet before it breaks through the back. Another technique is to mark the desired hole with big crosshairs so you can see if the hole is shifting, and if it is, you can “pull” or “push” the hole around while you drill..
 
If it's a critical location, mark the final size hole "ring" with a Sharpie, and eyeball the hole as it develops. You can put some "English" on the bit if it starts to wander.
 
Hopefully you are using a Unibit with only one ground cutting slot such as Irwin Unibit #10231.
The common multibits from the hardware store with two cutting slots make a mess of aluminum every time.
 
Thanks everyone for their timely advice. It's much appreciated.
Merry Christmas.

Scott
 
I have had better (though not always ideal) results from step drills with spiral flutes vs those with straight flutes. That said, setting up good optical guides so you can control the bit is a good idea.

Peter
 
Back
Top