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Deburring with sandpaper?

missile29

Member
Is it just me or is sandpaper an underutilized deburring tool?

Seems like there are all kinds of fancy deburring blades and tools, files, 3M wheels, and scotch brite pads, that we buy and use. And those are all great And have their place. But I’ve been finding that plain old sandpaper, in the 400-1000 grit range, is a great way to get into the little nooks and crannies between rib flanges and such. And it knocks down the tooling mark bumps on some of the thinner sheet metal parts easier than using a file.

I’ve been coming back and finishing up with red or grey scotch brite for good measure, but I’m not sure that’s even necessary after using 1000 (or 2000 or 3000) grit.

The one thing I’ve been extra careful about is making sure that I don’t let a folded edge of a piece of sandpaper cut a gouge in a radius or some other spot. That’s one thing I think scotch brite is more forgiving about.

So, have I been living under a rock and everybody deburs with sandpaper? Or is there some reason this is a bad idea?
 
I haven't started building yet, but I did take the Build Essentials course from Synergy Air. They encouraged us to use sandpaper to smooth the burrs on the inside of flanges, and personally I like the results for those hard-to-reach spots.
 
one no-no

I also use sandpaper in conjunction with other deburring tools (draw filing, scotch brite pads and wheel, speed hole deburrer etc.)

There is one big "no no" with sandpaper and that is using the black wet and dry silicon carbide type on aluminum. This is because the particles can contaminate the aluminum and cause corrosion.
 
Is it just me or is sandpaper an underutilized deburring tool?

Seems like there are all kinds of fancy deburring blades and tools, files, 3M wheels, and scotch brite pads, that we buy and use. And those are all great And have their place. But I’ve been finding that plain old sandpaper, in the 400-1000 grit range, is a great way to get into the little nooks and crannies between rib flanges and such. And it knocks down the tooling mark bumps on some of the thinner sheet metal parts easier than using a file.

I’ve been coming back and finishing up with red or grey scotch brite for good measure, but I’m not sure that’s even necessary after using 1000 (or 2000 or 3000) grit.

The one thing I’ve been extra careful about is making sure that I don’t let a folded edge of a piece of sandpaper cut a gouge in a radius or some other spot. That’s one thing I think scotch brite is more forgiving about.

So, have I been living under a rock and everybody deburs with sandpaper? Or is there some reason this is a bad idea?

Watched your video on this and I also was using the scotchbrite wedge technique that you put in a dremel tool. Gonna give your card board and tape method a try on the HS. Thanks for the videos btw.
 
There is one big "no no" with sandpaper and that is using the black wet and dry silicon carbide type on aluminum. This is because the particles can contaminate the aluminum and cause corrosion.

can you cite a reference for this?
 
I use a whole bunch of 320 grit aluminum oxide emory cloth to debur. Lincoln electric makes a 1" wide roll thats 25' long. Just as you said, its the best tool to get into all the nook of ribs. I find sandpaper especially useful on large sheet material because I'mm too scared to use high energy spinning tools on them. I usually go file, sandpaper, scotchbrite hand pad.
 
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paulvs

can you cite a reference for this?

The Licensed Aircraft Maintenance Engineer who did my stage inspections provided that advice (and so I immediately stopped using silicon carbide sandpaper). I now use aluminum oxide sandpaper between 240 and 400 grit.

The written reference is AC43.13-1B Table 6.1 "Abrasives for corrosion removal", viz:-

"Aluminum alloys except clad aluminum. Restrictions: Do not use silicon carbide abrasive."
"Clad aluminum. Restrictions: Sanding limited to removal of minor scratches."
 
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The Licensed Aircraft Maintenance Engineer who did my stage inspections provided that advice (and so I immediately stopped using silicon carbide sandpaper). I now use aluminum oxide sandpaper between 240 and 400 grit.

The written reference is AC43.13-1B Table 6.1 "Abrasives for corrosion removal", viz:-

"Aluminum alloys except clad aluminum. Restrictions: Do not use silicon carbide abrasive."
"Clad aluminum. Restrictions: Sanding limited to removal of minor scratches."

Wow, thanks for this! Up until the other day I was just using some sandpaper I happened to have around already. I’m not even sure the brand or type of abrasive, but it’s yellowish so I don’t think it’s SiC.

But! … I had just purchased an assortment of 3M Wet/Dry stuff from HD that, when I googled it, was indeed the Silicon Carbide type. I’m kindof irritated that I had to look it up online, as the packaging didn’t specify the abrasive type. So I guess I won’t be using that anymore!

Confession, I did already use it to clean up a few spots on the HS ribs while also deburring the holes in the flanges. Should I panic and try to scrub away any offending SiC? I assume my tail isn’t going to dissentigrate in mid air due to rampant corrosion caused by a little bit of sanding with the wrong stuff, but I will take extra care to clean those bits really well before priming.

For that matter, I assume any possible corrosion that might be caused by having used the the SiC would be quite limited if the whole thing is primed over.

Now to search and find somewhere to buy AO sandpaper, since the local big-box stores didn’t seem to have anything specifically labelled with abrasive type…
 
The Licensed Aircraft Maintenance Engineer who did my stage inspections provided that advice (and so I immediately stopped using silicon carbide sandpaper). I now use aluminum oxide sandpaper between 240 and 400 grit.

The written reference is AC43.13-1B Table 6.1 "Abrasives for corrosion removal", viz:-

Without intending to be contrarian, this is something I'd like to see investigated a bit more, such as why does the restriction exist. Perhaps it's for a good reason. Perhaps it's an old wives tale. I'd like to understand it better.

I note that a bit further down in AC43, under 6-136, it advises that removal of corrosion on aluminum alloy may be done with (among other things) aluminum oxide or silicon carbide (6-136-d-1-a). Later under 6-152 it does advise against silicon carbine for cast magnesium parts (6-152-e-1-a). If I'm reading correctly, this constitutes a contradiction to the table.
 
Without intending to be contrarian, this is something I'd like to see investigated a bit more, such as why does the restriction exist. Perhaps it's for a good reason. Perhaps it's an old wives tale. I'd like to understand it better.

I note that a bit further down in AC43, under 6-136, it advises that removal of corrosion on aluminum alloy may be done with (among other things) aluminum oxide or silicon carbide (6-136-d-1-a). Later under 6-152 it does advise against silicon carbine for cast magnesium parts (6-152-e-1-a). If I'm reading correctly, this constitutes a contradiction to the table.

Good point - that does seem like a contradiction.

I believe that the mechanism for corrosion has to do with a galvanic reaction between the aluminum and particles of carbon (in the SiC abrasive) left behind. It’s the same reason Van’s recommends against marking aluminum parts with a pencil in Section 5, though I confess I obviously didn’t make this connection before buying sandpaper.

That said, I also checked in section 5 where Van’s talks about sanding out scratches, and nowhere do they specify a type of abrasive or caution against using SiC-based paper. They suggest working your way up in grit, of course, up into the 1000+ range, and for what it’s worth, I’ve found that anything above 400 grit available at a local hardware store (read: Home Depot, etc.) is by default the black, wet/dry, SiC based stuff. Annoyingly, it doesn’t tell you the type of abrasive on the package, either. I had to check 3M’s web site.

And in fact, the 3M web site I looked on to determine what the paper I bought was made of recommended that very product for use on all metals, including aluminum, without any mention of corrosion risk. Then again, they’re in the business of selling me sandpaper, not advising me on galvanic corrosion risk. Further, they didn’t seem to offer any grit finer than 400 in something other than SiC. (Though some other manufacturers probably do.)

Long story short, based on common availability and lack of outright warnings in the plans or packaging, I suspect there are a lot of airplanes flying around out there that had SiC-based sandpaper used on them and they’re not disintegrating into a pile of aluminum dust.

Personally, I plan to avoid SiC based sandpaper going forward, and I did manage to find an AO-based paper at HD in 400 grit. It’s this weird purple-ish color, but I’m not picky about that. 3M’s site says its abrasive is aluminum oxide so it should be fine. 400 grit was as high as it went, but that grit was actually convenient for deburring steps somewhere between what I tend to do with a file or blade, and the final pass with scotchbrite, anyway, so I’m going to go with it for now. I’ll probably look online for some higher grit stuff down the road.
 
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