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Geoff Heap
Joined: 12 Jan 2006
Posts: 266
Location: Lindenwold, New Jersey
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 Posted: Tue Jan 17, 2006 6:49 am Post subject: Definitive hole deburring |
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First we need to get rid of the mindset that hole deburring is an unimportant distraction. It is an operation in itself. Think about
how many holes you will debur in your building process. Using the wrong tool will add countless hours to the process over the life of the project.Please buy the right tool and avoid being cheap. I've seen this question so many times over the years and someone always says to use a drillbit. Sorry guys this only works sometimes, usually with small diameter holes. No machinist would ever do this.The rotating blade is very good at this job.The most common brand name at MSCDIRECT.COM is the VARGUS. There are other brands, plus,I think SEARS sells something like it. One MSC debur set is from VARGUS (msc ORDER # 00424523). One handle and about a dozen blades for $3.92. One blade will almost last forever in aluminum. Add in a few steel parts and this set will build a couple of aircraft. This tool is great for holes about 3/8 dia. or larger. However, if the burr is thick and raised as a result of a dull drill, the resulting debur will be ugly.(same for using a drillbit). A smooth
file should be used first to get rid of the raised part. Then the deburring tool can take the sharp corner off the hole nicely. I'm Building a CH701 so my holes are mainly 1/8" and 5/32". For these sizes the drill bit approach can work fairly well but only if the original hole was made with a sharp drill which will produce a very small burr. However you can do a better and I think, quicker job with a small countersink tool in a pin vise/chuck holder(you still need the file if the burr is heavy). It looks exactly like the rotating blade tool holder but instead of "snap in/snap out" as with the rotating blade, it will hold anything round just like a drill chuck does. MSC sells Part # 06491906 (5/16 dia. capacity) for $21.72.(I spent a while looking up these part numbers). Now all you need is a small countersink to use in the pin vise. There are millions of them out there. Try MSC PART # 60316650. It is 90 degrees, 5/16" dia. with 1/4" shank (MSC Part # 60316655 $12.69). Now here's the important part. This tool and all coutersinks have 3 or more flutes. This gives stability and is the reason why a 2 flute drillbit cannot debur well. I have all these tools and use them constantly.If you don't buy them now you probably will later. The parts I list here total about $37 + shipping. You can find them cheaper and possibly locally at SEARS. Don't baulk at the cost. I have a rivet squeezer that I paid a bundle for and only needed it for less than a hundred rivets. The deburring tools I use ALL the time. I hope this helps put this problem to rest. It's a recuring question from new builders. Regards to the group....Geoff Heap.
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planejim(at)bellsouth.net
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| Posted: Tue Jan 17, 2006 4:47 pm Post subject: Definitive hole deburring |
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Hey Listers,
I agree completely with Geoff. I have done this stuff for nearly 50 years
and I am Chairman of the Basic Sheet Metal Workshop at the SunNFun Fly-In.
So for what its worth let me add a few thoughts. Many of my fellow
volunteers who teach in the SNF workshop also have many years of experience.
We nearly all prefer the offset handle with the three flut countersink bit
installed. They just aren't that expensive when you consider that you will
use the tool several thousand times during the construction of your metal
aircraft. Yes, occasionally you can't get that tool into where you need it.
Use the file or drill bit only when you must. If you were working with
2024-T3 and used a file you would be removing the Alclad which is there to
prevent corrosion. Corrosion under a rivet head is a bad place to have it.
6060-T6 isn't as critical. There is no Alclad because of the makeup of the
metal.
The main thing to remember when deburring is that the junction of the pieces
of metal and the rivet is the strongest when the hole is completely filled
with the rivet. Also, rivets primarily do their job in shear. If the
countersink is too deep, the sheetmetal acts as a shear on the rivet. If the
burrs keep the two pieces of metal apart as the rivet is set, the joint just
won't be as strong. The trick (which comes with practice) is to completely
remove the burr without countersinking the hole at all. One of the previous
Listers stated "I try to go maybe one thousandth into the hole" Not a bad
way to describe it. It's important to deburr properly but don't agonize over
it too much. I don't know of any General Aviation airplanes that have come
apart because of improper deburring!
Have fun building your airplane!
Jim Hoak 601HD 500.3 hrs
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