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Deburring and edge finishing

CPSONE

CPSONE

Well Known Member
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Just working on elevator counter weights and looked at a builder's website with good (actually excellent) photos for some insight. Viewing one of an elevator spar reinforcement plates and the parts were riveted together. The center hole for rod end middle of the platenut had the factory "stamped" sharp edge so was not deburred. Looked at a photo of an elevator rear spar by the control horn (riveted on), still has the raw looking cut marks as it comes from the factory on the end and edges looked sharp.
Correct me if I'm wrong and I apologize for the rant but you have to edge finish and deburr edges for these birds to last and be safe.
I'm not saying who's web page it was but just hope that this may create some awareness.
 
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What's the exact standard here? I've seen plenty of people insisting that deburring and edge finishing are not beveling operations. I've taken that to mean that if there are no actual burrs (which would keep parts from mating and be a cutting danger to skin) and if edges are smooth to the touch with no surface discontinuities (which would act as stress risers), then that's good enough. What specifically did you see visually that I should be looking for?

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Stephen
 
Looked at a photo of an elevator rear spar by the control horn (riveted on), still has the raw looking cust marks as it comes from the factory on the end and edges looked sharp.
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Posting the picture you are looking at would be helpfull.:)
 
a sample pic

Here's basically what it looked like.
This is one of my photos taken for an example and not the photo from the builder's site. My aim is not to point fingers but to create a reminder to smooth edges and de-burr. It's pretty clear in the builder manual but I've seen some bad, raw edges out there including many on the second hand 7A kit I have!
It's basically not de-burring at all from being missed which happens or just not bothering. The latter is the reason for my post.
In the photo you see the anchor bolt hole has been deburred with a swivel de-burring tool. The holes beside them have not been touched. In my case not match drilled yet either. The anchor bolt hole I saw on the builder's site had a raw punched hole factory sharp edge as they come out of the box. The backing plate and nutplate were all riveted together so there is a good chance it just got missed. Backing plate edges were finished very nicely actually. The end of the elevator spar looked untouched by any de-burring tool.
I try to adhere to the edge finishing and de-burring section in Van's manual. :)
349bbso.jpg
 
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CPSONE said:
I try to adhere to the edge finishing and de-burring section in Van's manual. :)
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Ah, got it Mike. I misunderstood your point, which seems to be less of "keep to the standard" and more of "don't skip any edges or holes." Thank you for that reminder, as it's one of my constant worries. I seem to triple check everything because I don't yet have a good QC system to indicate which prep work is done for each part. I bet that's something that naturally gets easier as a project progresses.

--
Stephen
 
deburring question

Since starting my build, the deburring part has had me confused. The manual says to deburr the edges of everything and shows a couple pictures. In my kit, the spars, doublers, and such look like they were cut with a plasma cutter and a slight bump every 6"-8" on the edge. They are pretty sharp too.

I don't know how far to go. I understand how in the skin, a hole could easily get a crack and split out. I can understand an edge being sharp and vibration against the skin or rivet could cause failure. I get it to some extent on a bolt hole, you don't want burrs rubbing against anything. Things like the holes in the center of the ribs and the lightening holes - I can't see as much of an issue. Of course, they all need to be inspected and smoothed over, but how much more?

I think I have been going overboard to make sure everything is rounded. I have read about how planes people have seen were not deburred as well as they thought it should be and it was considered poor workmanship. Does anyone know of an instance where poor deburring or the lack of deburring has caused cracks? I know of problems with fiberglass planes and poor bonding causing problems. I would like to know of problems that have been caused by lousy deburring - not what potentially could happen, but what has happened. Myself, I enjoy the forked edge deburring tool I use. I like the sanding pad and how it makes it look nice!
 
I have been running a file down every edge of metal. First I do it flat until the edge looks uniform (about 3 or 4 passes). Then I break the edges on both sides with about 3 more passes each. Then I run some 400g emery cloth along the edges. It goes very fast, and works much better for me than the edge shaver tool, that thing shaves off way too much, or catches and puts gashes in the metal. Or maybe I just don't know how to use it correctly.

I deburr every hole, but use a reamer to final size them first. There is very little burr with the reamer. If the holes are to big for the deburring tool (lightening holes and such), I use the emery cloth.

Maybe this is overkill, the manual does state if you can run your finger down them without catching they are good, but I like the way everything looks and feels, and it really doesn't take very long.
 
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Deburring

rockwoodrv9 said:
Since starting my build, the deburring part has had me confused. The manual says to deburr the edges of everything and shows a couple pictures. In my kit, the spars, doublers, and such look like they were cut with a plasma cutter and a slight bump every 6"-8" on the edge. They are pretty sharp too.

I don't know how far to go. ....

I think I have been going overboard to make sure everything is rounded. ....
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First a comment on the long edges of parts that have a slight bump every 6" to 8", this is not a plasma cut. What they use is a turret press which is a machine that moves the raw material around on a platform so that a fixed tool can punch holes. It is programmed to change the tooling as needed which includes long slotted punches that when used end to end will produce a long straight edge. At the end of one punch and the start of a the next you can have a slight imperfection or "bump", these should be smoothed on all parts, especially if it is a structural part like an elevator spar. A couple passes with a vixen file is all it takes.

There are two reasons for deburring parts, one is to insure parts are not held apart with a gap between them caused by the burr. The other is to prevent a starting point for a stress crack. You can go to extremes in not deburring and being too obsessive about deburring. If you can use your finger nail and feel a burr you need to to remove it. Likewise once the burr is gone don't think you have to add a large radius at each edge corner, a couple passes with a scotch bright pad or a scotch bright wheel is enough but don't over do it. If in doubt please talk to an experienced builder.

It is part of the learning experience when building an airplane to learn that this is not rocket science and it is not the space shuttle. Most parts do not have to be finished to microscopic perfection, just reasonable perfection. Some critical structural parts, such as spars should be given special attention but items like seat and wing ribs just have to have the burrs removed and edges smoothed enough to prevent cutting yourself when handling.

Good luck on your build.
 
Thanks

I appreciate the info here. I completely understand the need to get burrs off - especially when it could keep a rivet from making complete bonding. I have seen cracks in galvanized metal on HVAC units and ducting. I think I am doing fine on it and will not get too carried away. I have a builder, David from the forum coming down this week to give me a hand and check my work. He is the guy that gave me my first RV flight grin and has over 900 hours on his -9.
Have a good Sunday everyone.
 
rockwoodrv9 said:
I appreciate the info here. I completely understand the need to get burrs off - especially when it could keep a rivet from making complete bonding. I have seen cracks in galvanized metal on HVAC units and ducting.
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Dang....

I've never deburred all those HVAC ducts, I've been putting in, for the last 40 years! :)

For the RV, one of the best tools I used, was a 90 degree air grinder with 2" blue scotchbright (type) pads. Very quick for nice smooth edges, almost anywhere. Used a file, very little.
 
I edge finish pretty much everything. This debate though is where I think redoing the builders manuals will help clear up confusion. All the builders manuals make it sound like the aircraft will fall out of the sky if there is a nick that is palpable to the finger any where on the aircraft. Then when I call Vans regarding a nick in the edge they immediately refute the necessity of spending to much time fixing it. For instance, I had a couple of shipping damage nicks in my spar caps that were palpable to the finger nail. I sent a pic to Vans and they said not to worry about it (dress it mildly but don't spend a lot of time on it). They also proceeded to send me pictures of the RV-12 spar which is plasma/laser cut with sharp edges and cutting marks every 6-8 inches. He sent me those to demonstrate that the spar caps were pretty rough and needed no finishing. So the builder is left to wonder...what is to much, what is to little?
I think modernizing the build manuals with color pictures would help a lot. In defense of what they said my Cessna 172 was not edge finished or deburred at all and it is 41 years old and still going strong.
 
Burr on hole

One thing that has confused me a bit as well is the burr on a rivet hole. I have read multiple "sheet metal construction basics" type books and they all seem to say the same thing about construction. From what I can gather, we are going way overboard with what is considered acceptable.

Of course most people want this thing to be beautiful, but if the concern is about basic safety, the books description of acceptable rivets is pretty far off what I have been told by many builders. Many of my practice rivets do not fit the rivet gauges I have purchased, but when I take a micrometer and measure based on mil spec, they spec out as "well within specs".

Same for the hole burr. Many holes I have drilled on my practice kits have a burr I can feel, but using many different methods of deburring ends up giving me a visible chamfer before removing the burr. These books seem to have told me to remove large hanging pieces of metal and if the remaining burr doesn't leave the panels raised from one another or prevent the rivet from laying flat, good enough.

Am I all wrong?
 
How are the Quick Builds done ?

I've not seen a QB so can someone tell me how much effort they put into it. Deburring is a thankless job, and it seems there is a difference in how much is appropriate. Vans must approve the parts leaving their warehouse.

Erik
 
I was over at jdeas' shop this evening, and we were looking at the edges of the fuselage skins on his QB -7...I was looking closely at how they were finished, something I noticed on another buddy's -8 when we were building it. The edges of the skins are *really* nice, and seem to have been machined somehow to put an extremely consistent, extremely smooth "bevel" on them. I never did find out how they did that, because I would liked to have done the same on my SB -7A.

It looks very clean and professional, even under an 8X loupe. Nice work.
 
A homemade tool like this can quickly and easily put a nice bevel/edge on skins before installation -

vixen%20file.jpg


It's simply a piece of a vixen file and a piece of wood.

Pic shamelessly stolen from an EAA chapter site....

I've found you don't even need the mounting screws, some RVT type "goop" glue can be used instead.
 
Hmmmmmm, I hope the tool companies that are members here are seeing this...


az_gila said:
A homemade tool like this can quickly and easily put a nice bevel/edge on skins before installation -

vixen%20file.jpg


It's simply a piece of a vixen file and a piece of wood.

Pic shamelessly stolen from an EAA chapter site....

I've found you don't even need the mounting screws, some RVT type "goop" glue can be used instead.
Click to expand...
 
LAMPSguy said:
<snip> Many of my practice rivets do not fit the rivet gauges I have purchased, but when I take a micrometer and measure based on mil spec, they spec out as "well within specs". <snip>
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Keep in mind that all gauges that I know have dimensions of a perfect rivet. Since that is nearly impossible you then have to compare the tolerance in each direction to what the gauge is telling you. Two sets of gauges for go/no-go would be an option, but I doubt they would get used.

Does anyone on the list have access to a laser or waterjet cutter for small batch work? We could make up a small batch of go/no-go and see if there is interest. Perhaps anodize on green and one red?
 
re: long edge tool

Hello Mike and Gil,
I used my Vixen file w/o handle a LOT on long straight edges. Oriented the file nearly "lengthwise" with the edge to smooth those tooling nicks mentioned above that appear regularly on long edges.

I also learned that alternating use of the file's two sides will eliminate those "chatter" bumps that will appear after a couple of passes. (Harmonics. I remembered some physics!)

Generally 3 or 4 passes total followed by gentle application of the Hook deburring tool and then light Scotchbrite pad did the trick. Smoooooth!

I know this is overkill to some, just another opinion and experience.

Dave
 
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