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Deburr, deburr and more deburr....

J

JurgenRoeland

Well Known Member
I have had a lot of discussions with several folks on deburring edges of the kit parts or as we tend to call it: the edge prepping.

My usual procedure is: vixen file to remove the CNC cutting marks, v-deburr tool to break the edges (more or les for saving your 3M scotchbrite wheel), followed by scothbrite wheel (either the large one on small and thicker parts or the small 1" wheels on the die grinder for long edges with small grinded tracks).
After that, I use 500 grit sandpaper to smooth it further down.

This last step is where the big debate starts.

I talked to some people who told me that using the 500 grit sandpaper makes the edge finish actually worse then it was after the scotchbrite finishing with the die grinder.

So, my question is, have I been doing all this sandpaper work for the last years for nothing (or worse, making it less good).
 
Scotchbrite Pads

Try Maroon Scotchbrite pads, usually found next to the bondo in in your favorite auto supply store, sometimes found in Walmart. Really helpful in tight places and lightening holes.
 
For the majority of my project I've used only the 6" scotchbrite wheel on a bench grinder and called it good. The instructions call for a satin finish, and I believe thats what I get with a couple of passes on the wheel. My bench grinder is currently Tango Uniform so I've been using a file followed by a 2" scotchbrite wheel in a die grinder. Sure is tedious.

According to my log, I edge deburred both wing rear spars and the aileron bracket reinforcement plates in a little over 45 minutes. Pay no attention to the stylish goggles;):
FP30042012A0004D.jpg
 
Per the EAA Workshop videos

Per the EAA guys... If you run your finger along the edge with moderate force & dont get any cuts, you are in good shape. Most of us go above & beyond that with scotch brite wheel, pads, sand paper etc. Is it nessasary, probably not. As long as there is a clean edge, you are good to go... Vixen file & the V-blade should get you to the "suffciently" deburred edge. Personally, if you are going to this extent on the edges, I'd be much more concerned with over deburring rivet holes. :eek:.. I'm guilty of this :eek:
 
On the older kits, for skins you did not have to trim, you had deviations every few inches from tooling that left a slight bump or tooling mark. You had to take your vixen file and smooth the edge first as the vtool would catch the little bumps.
You would file 90 deg. to the edge of the skin creating a burr and then use the vtool to knock it down. A couple of passes with the scotch wheel and done.
Perhaps the newer kits do not have these deviations elliminating the need to file?
 
Edge Debur

I do the following.

1) Vixen file to remove all tooling marks.
2) Dove tail edge deburring tool.
3) 220 sandpaper to remove the chatter marks from the dove tail.
4) Polish with 1" wheel.

This has been very tedius but it leaves a nice polished edge.
 
JurgenRoeland said:
I have had a lot of discussions with several folks on deburring edges of the kit parts or as we tend to call it: the edge prepping.

My usual procedure is: vixen file to remove the CNC cutting marks, v-deburr tool to break the edges (more or les for saving your 3M scotchbrite wheel), followed by scothbrite wheel (either the large one on small and thicker parts or the small 1" wheels on the die grinder for long edges with small grinded tracks).
After that, I use 500 grit sandpaper to smooth it further down.

This last step is where the big debate starts.

I talked to some people who told me that using the 500 grit sandpaper makes the edge finish actually worse then it was after the scotchbrite finishing with the die grinder.

So, my question is, have I been doing all this sandpaper work for the last years for nothing (or worse, making it less good).
Click to expand...

I found this chart

SCOTCHBRITE GRIT CHART

7445 - White pad, called Light Duty Cleansing - (1000)
7448 - Light Grey, called Ultra Fine Hand - (600-800)
6448 - Green, called Light Duty Hand Pad - (600)
7447 - Maroon pad, called General Purpose Hand - (320-400)
6444 - Brown pad, called Extra Duty Hand - (280-320)
7446 - Dark Grey pad, called Blending Pad (180-220)
7440 - Tan pad, called Heavy Duty Hand Pad - (120-150)

So your 500 grit is actually a little finer than the maroon ScotchBrite and should do no harm and will even be a little smoother. It is probably a little harder to use though.

The equivalent grits are in this 3M document on page 92 and correlate with the easy to read chart above -

http://multimedia.3m.com/mws/mediawebserver?66666UF6EVsSyXTtMXfV5XTaEVtQEVs6EVs6EVs6E666666--
 
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Selection

For hand deburring I have a variety of different options I use as necessary for different situations. It all depends on if I need to remove material, clean off big burrs, small burrs, or finish. Use what I need to do to get the result I want.

I have a "Speedy Burr 2" from Aircraft Spruce, brown scotchbrite, green scotch brite, vixen file, half round file, chainsaw file, emery cloth, 400grit and 600grit sand paper.

I almost always use a combination depending on the edge. Most recently I was cleaning up the edges of some wing skins. I used the Speedy Deburr, and 400grit sand paper. Then there were a couple scratches in the skin surface where I used 400grit to remove the scratch, then 600grit to finish it.
 
Thanks for all the responses guys.
Looks like I will continue to finish my edges after the 3M wheel with the 500-600 grit sandpaper for a final finish.
 
The purpose of all this is to remove any pre-existing edge flaw or crack which could grow when stressed to eventually fail under load.

If you clean up the edge far enough that there's no flaws visible with a 10x magnifying glass, you've done enough. While it's nice to polish the edges, it's not necessary.

As a reference point, most of the sheared edges on my 1955 Cessna 180 are left in the sheared condition. I'd NEVER do that. But the C-180 has around 3,700 hours or so and is doing just fine.

Dave
 
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