I decided to prime only what van's said needs to be primed. My question is this, if you sand on the ribs with scotch brite, do you have to prime it afterwards? I am assuming that on the ribs you can sand the whole thing and not have to worry about it. Thats what we did at A&P school when we were recovering a piper cub. Never primed it afterwards. I am now putting on the stiffeners on the rudder and did alot of sanding to get them smooth after I cut away the portion that you had to. I see it's got a shine that the ribs don't and was wondering if I sanded off the protective covering and they need to be primed now. Any ideas?
Van's Air Force
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quick question about aluminum priming
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AX-O
Well Known Member
They should be primed. Sounds like you removed the protective coating off the alum if it is not shiny anymore. But you will get people telling you that they never did and their airplane is fine. When I first started building the 8, I primed everything. Now I just prime the locations where parts overlap.
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burgundyja
Well Known Member
ha ha just a quick question about priming. lol 
I think I figured out how to tell what needs to be primed if you sand them. They have the blue protective tape on them. Am I right? I noticed the ribs never did but the stiffeners do. Guess I'll prime them and be done with it. As far as the ribs are concerned, I don't think it matters if you sand them. Like I said, we never primed them in A&P school.
I'm not sanding the whole thing, just using scotch brite to break the edges and going over the holes after final drilling. You end up sanding more than just the edges from the scotch brite rubbing against other parts. I primed the stiffeners anyways. They were small and only took 5 minutes. What do you use to break the edges? Anything other than scotch brite that works better and gets less of the stuff you don't want sanded?beattiema said:
Sam Buchanan
been here awhile
A Scotchbrite wheel on an air die grinder is a great way to quickly deburr nearly any edge:
Don't worry about the grooves in the wheel---they are your friends. Just hold the grinder at slightly less than perpendicular to the skin edge and you can deburr both edges in one pass.
Drilled holes get deburred with a deburring bit in a cordless screwdriver. Don't obsess over deburring, just take care of the burr and move on. There is no need to polish the edges or chamfer the holes.
Happy building!
Thanks for the info Sam. That does look faster than what I've been doing. I haven't seen that many burrs at all. Most wipe away with a towel but for the stubborn ones, I just turn a counter sinking bit by hand a turn or two. Seems to work well just hard to hold on to. After I look the holes over I've just been wiping them good with schotch brite to make sure they are nice and burr free. Guess that's how I rub off the protective coating and that's why I'm in this thread. It works really well for the ribs that don't have the coating but for the other shiny stuff, I have to come up with some other way. Do you run a file or anything along the edge of the skins? I see that every 3 or 4 inches there is a little bump from where they stamped it out. I've been using a fine file to knock them off but wonder if its really necessary. I want to make sure it's done right but everyone has their own opinion on that as well. Guess thats why its called learning.
Sam Buchanan
been here awhile
Go back and read my post again.
The 2" wheel is the only method needed to deburr skin edges. If the edges aren't sharp enough to be uncomfortable when you run your fingers along the edge...they are good to go.
By the way, the ribs and bulkheads are Alclad like the skins. They look different due to the forming process.
Good luck with your project!
Sam Buchanan
been here awhile
The 2" Scotchbrite wheel and the mandrel needed to use it with the die grinder should be available from Cleaveland and Avery. You will find the little wheel on your die grinder to be one of the most often used tools in your shop.
For some reason, the 3M light deburring wheels seem to only be available in 1" and 6" sizes. The cut and polish wheels are available in 1", 2" and 6" sizes. I'd really like to find a 2" light deburring wheel. I find that the 1" gets used up too quickly and the cut and polish can be too agressive for simple edge polishing. Anybody know a source? I've checked Avery, Cleaveland, Planetools, Aircraft Spruce...Sam Buchanan said:
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az_gila
Well Known Member
Not Silicon Carbide
Boris... check what you buy...
Many of the 3M products are Silicon Carbide and are not recommended for Aluminum.
Check the 3M part number if the first letter is "S" then it's not the right stuff. We should be using "Aluminum Oxide" which would have a "A" as the first letter.
The "3M Light Deburring wheels" have numbers like 8SFIN which is Density=8, S=Silicon Carbide, FIN=Fine grit.
The MSC catalog seems to be a good reference... check the adjacent catalog pages.
http://www1.mscdirect.com/CGI/NNPDFF?PMCTLG=00&PMPAGE=881
http://www1.mscdirect.com/CGI/NNPDFF?PMCTLG=00&PMPAGE=878
The silicon carbide discussion and link to AC43.13 is here...
http://www.vansairforce.com/community/showthread.php?t=20009&highlight=silicon+carbide
UPDATE...
The 2 inch ones you want are here at MSC... again, get the "A" ones...
http://www1.mscdirect.com/CGI/NNPDFF?PMCTLG=00&PMPAGE=884
gil in Tucson
borislav said:
Boris... check what you buy...
Many of the 3M products are Silicon Carbide and are not recommended for Aluminum.
Check the 3M part number if the first letter is "S" then it's not the right stuff. We should be using "Aluminum Oxide" which would have a "A" as the first letter.
The "3M Light Deburring wheels" have numbers like 8SFIN which is Density=8, S=Silicon Carbide, FIN=Fine grit.
The MSC catalog seems to be a good reference... check the adjacent catalog pages.
http://www1.mscdirect.com/CGI/NNPDFF?PMCTLG=00&PMPAGE=881
http://www1.mscdirect.com/CGI/NNPDFF?PMCTLG=00&PMPAGE=878
The silicon carbide discussion and link to AC43.13 is here...
http://www.vansairforce.com/community/showthread.php?t=20009&highlight=silicon+carbide
UPDATE...
The 2 inch ones you want are here at MSC... again, get the "A" ones...
http://www1.mscdirect.com/CGI/NNPDFF?PMCTLG=00&PMPAGE=884
gil in Tucson
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Uh-oh... I'm pretty sure my light wheels are "S".az_gila said:
Both Avery and Cleaveland sell the "S" wheels with no indication that they should not be used on aluminum. In fact, Avery specifically recommends them "to radius and deburr edges of aluminum parts". Not cool...
http://www.averytools.com/cart/p-349-light-deburring-wheel--7s-fine-grade-softer.aspx
Thanks!The 2 inch ones you want are here at MSC... again, get the "A" ones...
skyyking56
Well Known Member
S = soft ?
Hi Boris..
I'm going to guess that the 7S is soft and is NOT a 3M part number.
I think that Avery's would know better from all of the good things I hear about them. Please someone correct me if I'm wrong.
Maybe call Bob Avery to verify and then post this when you find out.
Thanks,
Jim
7A Wings
Hi Boris..
I'm going to guess that the 7S is soft and is NOT a 3M part number.
I think that Avery's would know better from all of the good things I hear about them. Please someone correct me if I'm wrong.
Maybe call Bob Avery to verify and then post this when you find out.
Thanks,
Jim
7A Wings
az_gila
Well Known Member
3M numbers...
http://www.averytools.com/cart/pc-76-43-6-scotchbrite-cutting-and-polishing-wheel.aspx
The small wheels sold are of the "A" type...
http://www.averytools.com/cart/pc-355-43-scotch-brite-cutting---polishing--wheel.aspx
I'd be interested to hear the response....
The AC 43.13-1B link is here... table on second page of this sub-section...
http://www2.tech.purdue.edu/at/courses/at308/Technical_Links/Ac43-13-1B/CH6_7.pdf
gil in Tucson
It appears that Avery is using the 3M numbering system. Their "Vans recommened" 6 inch wheel is a "7A" wheel.skyyking56 said:
http://www.averytools.com/cart/pc-76-43-6-scotchbrite-cutting-and-polishing-wheel.aspx
The small wheels sold are of the "A" type...
http://www.averytools.com/cart/pc-355-43-scotch-brite-cutting---polishing--wheel.aspx
I'd be interested to hear the response....
The AC 43.13-1B link is here... table on second page of this sub-section...
http://www2.tech.purdue.edu/at/courses/at308/Technical_Links/Ac43-13-1B/CH6_7.pdf
gil in Tucson
clevtool
Well Known Member
3M Wheel Question
I just checked with 3M tech support. They say that 'there should be no problems using Silicon Carbide Wheels on Aluminum. Contamination should not cause any problems anyway, but the only way the s.c. could contaminate the aluminum is by embedding and the wheels would have to run at an extremely high speed to cause this to happen. This kind of speed would exceed the max rpm rating on the wheel.'
A quick google search shows that there are actually alloys out there that are a mixture of silicon carbide and aluminum, so contamination there does not seem to be an issue.
We have been selling these wheels for over 15 years and I am sure Avery's have been for equally as long with no adverse results.
What is the best primer to use?
Mike Lauritsen
Cleaveland Aircraft Tool
I just checked with 3M tech support. They say that 'there should be no problems using Silicon Carbide Wheels on Aluminum. Contamination should not cause any problems anyway, but the only way the s.c. could contaminate the aluminum is by embedding and the wheels would have to run at an extremely high speed to cause this to happen. This kind of speed would exceed the max rpm rating on the wheel.'
A quick google search shows that there are actually alloys out there that are a mixture of silicon carbide and aluminum, so contamination there does not seem to be an issue.
We have been selling these wheels for over 15 years and I am sure Avery's have been for equally as long with no adverse results.
What is the best primer to use?
Mike Lauritsen
Cleaveland Aircraft Tool
az_gila
Well Known Member
Question...
Actually, my question would be...
"Can you substitute a similar "A" for aluminum oxide wheel for this function, just like Vans and the FAA recommend?"
Maybe... but they use the word "should", while AC43.13-1B uses the words "Do not use silicon carbide abrasive"clevtool said:
I think this is a way different metallurgical case... are any of those alloys in regular GA use?
Not really a good example when it comes to long term corrosion control... any real testing been done?
Actually, my question would be...
"Can you substitute a similar "A" for aluminum oxide wheel for this function, just like Vans and the FAA recommend?"
Separate discussion....
Thank you for the response..... gil A
clevtool
Well Known Member
3M Offerings
Just a little more digging shows that the closest aluminum oxide 3M wheel to the 'soft' we carry is the 6"x1"x1" '5AFIN' That is a 5 density which is 2.5 times harder than the wheel that we currently offer but it is the fine grade. I can get them 3 at a time for just under $70. They are stock so only should take a week or so. I can also get the 1"x1"x3/16" in qty of 50 for $6.00 also 5AFIN.
Just a little more digging shows that the closest aluminum oxide 3M wheel to the 'soft' we carry is the 6"x1"x1" '5AFIN' That is a 5 density which is 2.5 times harder than the wheel that we currently offer but it is the fine grade. I can get them 3 at a time for just under $70. They are stock so only should take a week or so. I can also get the 1"x1"x3/16" in qty of 50 for $6.00 also 5AFIN.
3m wheel question:
I also called 3M tech support today about the "S" vs. "A" wheels issue(#800-364-3577). Silicon carbide is a natural element that is mined from the earth(not manufactured from oil, steel, etc.) and (silicon carbide) is the more prefered abrasive over aluminum oxide in the metal finishing industry due to it's grandular structure & the way it stays sharp while wearing down. The tech rep. I spoke with mentioned that in the Seattle area (i.e. Boeing area) many of the shops doing contract aircraft work use (& prefer) the silicon carbide abrasives for finish work on new aircraft parts. He went on to say that this issue seems to surface every 3 or 4 years; and 3M has seen no history of corrosion from the use of this type of abrasive on finishing new parts.
I looked in AC43-13 under Chapter 6 (Corrosion Protection....) then to Section 7, then to the Table 6-1 ........... it shows "do not use silicon carbide abrasives...".
I then read on a few pages; go to 6-136 (Examples of removing corrosion from aluminum and aluminum alloys); then to (1) Non-Powered Corrosion Removal; then read (a) "The removal of corrosion products by hand can be accomplished by use of aluminum grit and silicon carbide abrasive, such as non-woven, non metallic, abrasive mat (MIL-A-9962), abrasive cloth, and paper. Aluminum wool,.........." Further down in (c) it mentions "Steel wool, emery cloth, steel wire brushes (except stainless steel) should not be used............." I could not find anything in AC43-13 concerning finishing of new parts; just corrosion protection. Leaves me with a lot more questions than answers...................
A quick bit of history here: In the early days of RV building the west coast builders were light years ahead of everyone; one of the trends was to use a 3M light Deburring Wheel for smoother & quicker deburring, and the wheel everyone was looking for was the "7S" (silicon carbide). Like Mike & Buzz at Cleaveland, we stocked the wheels recommended by Van's as well as the softer wheel sought by some of the builders. Looking back at past years sales it appears (from my figures) that about 95% of the builders bought the 7A MED wheel (recommended by Van's) & about 5% chose to buy the softer 7S wheel -- a very small percentage per my records.
I still do not profess to be anywhere close to an expert in the aircraft tool buisness (even after 20 years I'm still learning new things!!) so my thoughts are to anyone that has questions or reservations about using the silicon carbide wheels, call 3M and talk to them, keep up with postings here -- I'm sure there will be more on this to follow (in the RV community I'm sure there is someone out there with much more expertice on this subject); then decide what is best suited for your own project.
Sorry this was so long winded..............appreciate everyone's interest & input. Hope this helps everyone.
Regards;
Bob Avery / Avery Tools, LP
I also called 3M tech support today about the "S" vs. "A" wheels issue(#800-364-3577). Silicon carbide is a natural element that is mined from the earth(not manufactured from oil, steel, etc.) and (silicon carbide) is the more prefered abrasive over aluminum oxide in the metal finishing industry due to it's grandular structure & the way it stays sharp while wearing down. The tech rep. I spoke with mentioned that in the Seattle area (i.e. Boeing area) many of the shops doing contract aircraft work use (& prefer) the silicon carbide abrasives for finish work on new aircraft parts. He went on to say that this issue seems to surface every 3 or 4 years; and 3M has seen no history of corrosion from the use of this type of abrasive on finishing new parts.
I looked in AC43-13 under Chapter 6 (Corrosion Protection....) then to Section 7, then to the Table 6-1 ........... it shows "do not use silicon carbide abrasives...".
I then read on a few pages; go to 6-136 (Examples of removing corrosion from aluminum and aluminum alloys); then to (1) Non-Powered Corrosion Removal; then read (a) "The removal of corrosion products by hand can be accomplished by use of aluminum grit and silicon carbide abrasive, such as non-woven, non metallic, abrasive mat (MIL-A-9962), abrasive cloth, and paper. Aluminum wool,.........." Further down in (c) it mentions "Steel wool, emery cloth, steel wire brushes (except stainless steel) should not be used............." I could not find anything in AC43-13 concerning finishing of new parts; just corrosion protection. Leaves me with a lot more questions than answers...................
A quick bit of history here: In the early days of RV building the west coast builders were light years ahead of everyone; one of the trends was to use a 3M light Deburring Wheel for smoother & quicker deburring, and the wheel everyone was looking for was the "7S" (silicon carbide). Like Mike & Buzz at Cleaveland, we stocked the wheels recommended by Van's as well as the softer wheel sought by some of the builders. Looking back at past years sales it appears (from my figures) that about 95% of the builders bought the 7A MED wheel (recommended by Van's) & about 5% chose to buy the softer 7S wheel -- a very small percentage per my records.
I still do not profess to be anywhere close to an expert in the aircraft tool buisness (even after 20 years I'm still learning new things!!) so my thoughts are to anyone that has questions or reservations about using the silicon carbide wheels, call 3M and talk to them, keep up with postings here -- I'm sure there will be more on this to follow (in the RV community I'm sure there is someone out there with much more expertice on this subject); then decide what is best suited for your own project.
Sorry this was so long winded..............appreciate everyone's interest & input. Hope this helps everyone.
Regards;
Bob Avery / Avery Tools, LP
az_gila
Well Known Member
Thank you...
Bob and Mike... thank you for your reply and checking... we do appreciate the vendors that help builders... (see a separate rivet thread... ...).
This whole issue is somewhat obscure, and not well documented... , however, given a choice, I believe most builders would go for the recommended material...
I'm a bit confused over your statement...
"Looking back at past years sales it appears (from my figures) that about 95% of the builders bought the 7A MED wheel (recommended by Van's) & about 5% chose to buy the softer 7S wheel -- a very small percentage per my records."
Isn't the "7" in the part number the density ("hardness") of the ScotchBrite wheel, so the "7S" should be no softer than the "7A"? .. or is the variation in how fine the wheels are?
gil A
Bob and Mike... thank you for your reply and checking... we do appreciate the vendors that help builders... (see a separate rivet thread...
...).This whole issue is somewhat obscure, and not well documented...
, however, given a choice, I believe most builders would go for the recommended material...I'm a bit confused over your statement...
"Looking back at past years sales it appears (from my figures) that about 95% of the builders bought the 7A MED wheel (recommended by Van's) & about 5% chose to buy the softer 7S wheel -- a very small percentage per my records."
Isn't the "7" in the part number the density ("hardness") of the ScotchBrite wheel, so the "7S" should be no softer than the "7A"? .. or is the variation in how fine the wheels are?
gil A
Gil:
The first number is the density of the wheel -- "2" is soft and "9" is hard (goes 2,3,4,5,6,7,8,9) -- so you have 7 choices of densitys; then the next letter is the abrasive material (A or S) - so you have 2 choices there; then you have the grades --VFN=very fine / FIN=fine / MED=medium / CRS=course / XCRS=extra course -- so 5 choices there; then you get into the different kind (application) of wheels -- you have: cut & polish / clean & strip / general purpose / SST / light deburring / EXL wheels (to name just a few) -- so 6 more choices there. A "7" density in one style may feel different than a "7" density in another style. The 7S wheel we sell can be compressed some between your fingers; whereas the 7A cut & polish wheel is hard (density) as a piece of wood.
Get you hand on a 3M abrasives catalog and the choices will make your head spin......................
The softer / less density wheels wear down much faster than the (Van's recommended) cut & polish 7A MED. All these wheels are $$ expensive so try to get the one that will last the longest for your application. 3M has a lot of technical information available for those that desire to explore this subject further.
Bob
The first number is the density of the wheel -- "2" is soft and "9" is hard (goes 2,3,4,5,6,7,8,9) -- so you have 7 choices of densitys; then the next letter is the abrasive material (A or S) - so you have 2 choices there; then you have the grades --VFN=very fine / FIN=fine / MED=medium / CRS=course / XCRS=extra course -- so 5 choices there; then you get into the different kind (application) of wheels -- you have: cut & polish / clean & strip / general purpose / SST / light deburring / EXL wheels (to name just a few) -- so 6 more choices there. A "7" density in one style may feel different than a "7" density in another style. The 7S wheel we sell can be compressed some between your fingers; whereas the 7A cut & polish wheel is hard (density) as a piece of wood.
Get you hand on a 3M abrasives catalog and the choices will make your head spin......................
The softer / less density wheels wear down much faster than the (Van's recommended) cut & polish 7A MED. All these wheels are $$ expensive so try to get the one that will last the longest for your application. 3M has a lot of technical information available for those that desire to explore this subject further.
Bob
az_gila
Well Known Member
Density is density, or is it?
....thanks for the clarification.... gil A
Thanks Bob... I had already decoded the numbering system (see earlier posts) but, dumb me, thought that 3M would be consistent in their rating of densities when describing wheels.... bad assumption.bob avery said:
....thanks for the clarification.... gil A
coastalflyer
Member
Great to have you suppliers on here! It further reinforces my feeling that this is the center of the homebuilders universe....even though I'm not building an RV! I have been using a 7S wheel for my entire Murphy Rebel build (airframe almost done). I sure hope it doesn't fall apart as a result. I can attest that it does wear down pretty quick, but I still have a little nub left, and I'm trying to stretch it. A Rebel has about 3 times the number of rivets of an RV I think (a guess), so deburring is a big part of the work. The 7S wheel is a super duper time saver for hole and edge deburring. Any part I can fit up next to my drill press (that's
where I run my 7S wheel) gets deburred that way. It has the added benefit (a big one) of not chamfering the hole as with a deburring tool or bit. ZZT, ZZT, ZZT, ZZT...done!
So I am now forced to subscribe to the point of view that silicone carbide wheels won't contaminate my parts and make my plane week. I sure am not going to start over!
where I run my 7S wheel) gets deburred that way. It has the added benefit (a big one) of not chamfering the hole as with a deburring tool or bit. ZZT, ZZT, ZZT, ZZT...done!
So I am now forced to subscribe to the point of view that silicone carbide wheels won't contaminate my parts and make my plane week. I sure am not going to start over!
