Basis question
 

Anyone have a good idea/technique for deburring the back side of a hole that is inaccessible with the standard countersink/deburring tool? Been struggling with this issue during entire build.

Would the tip of a file reach the hole? A fine file rubbed over the surface might debur.

I've also found that a good scrubbing with purple scotchbrite pads debur decently, as long as you don't mind the surface getting scratched up. If this hole is inside the plane, you probably don't mind scratches.

Here's a good tool for that task:

https://www.aircraftspruce.com/catal...?clickkey=7152

Burraway tool
 

Debur 3/32, 1/8 (and some other larger sizes) front and rear side of hole in single pass. Loved this when doing the flange holes on ribs or hard to access areas.

Blind Deburring Tool
 

I've used these with great success
https://www.noga.com/Products/rvcn/R...20countersinks

Look under "Tools"

Right angle debur tool
 

If there's room, I use this.
https://drive.google.com/open?id=0B7...VRCSlNLUjI4c0E

I use exactly what Mike S posted. Just have go have the right attachment, you want the deep U attachment.

I picked up a set of these in a bunch of sizes off of Ebay...new ones are pricey. Replacement blades are available, as well, and not very expensive. You can set the tension on them, as well, to more or less aggressive in how much metal they remove.

A terrific tool, one I really liked and highly recommend.

I highly recommend getting the 3/32 and 1/8 Burraways. A little pricey, but well worth it. https://cogsdill.com/products/deburring-tools/burraway
Their website has nice videos showing how they work, how to change blades, etc. I think I picked mine up from ATS or Brown Tools.

Blind deburring tools
 

Thanks for all the suggestions. Had limited success with “hooked” deburring tool. Gonna look at the burraway type.