Set screws for aluminum plate

[Matt-Aburg]

The winner is.............. big drum roll !!!! ....... !!!!!! ......

Green PLA plugs, manufactured by ME. I got 100 percent refund for Grainger plastic set screws... Note to all, They are shit, don't ever buy them !!!

 

[whydontu]

back to the original question. (45 years of supplying aluminum and stainless steel valves in marine and pulp mill environments)

Yes, stainless steel and aluminum form a galvanic couple and will corrode. BUT, it’s not that simple. Relative mass also comes into play. Small area/mass of stainless in a large area/mass of aluminum is generally OK, stainless fasteners in aluminum boats work just fine.

Aluminum rivets in stainless sheet dissolve in weeks in offshore BC environments, stainless bolts in aluminum motor mounts last forever.

Brass set screws would also work fine.

Can Stainless Steel and Aluminum Be Used Together?

When aluminium makes contact with stainless steel fasteners, corrosion can occur. However, the two metals can be used together, read more!

www.marshfasteners.com

 

[Matt-Aburg]

back to the original question. (45 years of supplying aluminum and stainless steel valves in marine and pulp mill environments)

Yes, stainless steel and aluminum form a galvanic couple and will corrode. BUT, it’s not that simple. Relative mass also comes into play. Small area/mass of stainless in a large area/mass of aluminum is generally OK, stainless fasteners in aluminum boats work just fine.

Aluminum rivets in stainless sheet dissolve in weeks in offshore BC environments, stainless bolts in aluminum motor mounts last forever.

Brass set screws would also work fine.

Can Stainless Steel and Aluminum Be Used Together?

When aluminium makes contact with stainless steel fasteners, corrosion can occur. However, the two metals can be used together, read more!

www.marshfasteners.com

really, i would prefer not to cbore my thread engagement away... though it is in design already. And all the pretty colours on the plate.... LOL

 

[PeterT]

Is it the perpetual flood/evaporation cycles of water based coolant in CNC that is causing the corrosion issue to begin with? Maybe coolants don't have a sufficiently high percentage of oily content in their emulsions which might help? Would these fastener/material combinations even be a concern in a bolted assembly in air? How about humid air? I always assumed it was salt water environment that aggravated the rate of corrosion, but maybe fresh water environments are similar. Chemistry is not my strong suite.

My only data point is model engines, predominantly aluminum allows & typically black oxide fasteners. Maybe its the oily/fuel environment that self protects, but the only time I see corrosion issues is a puddle of fuel. Methanol is hydroscopic & apparently many synthetic oils break down & become acidic? aggravating corrosion. Not sure if this is an issue on say gasoline burning oil pumped aluminum motorbike type engines? I don't think there are many aluminum or stainless bolts in there are there? Interesting stuff.

 

[phaxtris]

3/8 aluminum plate with a 1/2 ss thru bolt, size on hole, so a tight fit

This is the result after about 4 years installed,dry exterior service, I had to hammer the bolt out the the plate it was stuck so bad, had it been threaded there would be nothing left

 

[thestelster]

Would a sacrificial anode work?

 

[PeterT]

3/8 aluminum plate with a 1/2 ss thru bolt, size on hole, so a tight fit
This is the result after about 4 years installed,dry exterior service, I had to hammer the bolt out the the plate it was stuck so bad, had it been threaded there would be nothing left

Amazing. I'm going to pay more attention to this. I've read about some post-crash FS aircraft horror stories where the wrong fastener or was used & became the failure mechanism. Some were over-houred but others were corrosion related. It was a bit disturbing because it was traced to countries buying well used jets near the end of useful life, parked in humid salt air conditions & questionable repair/maintenance using black market parts. I didn't quite the gist of it but apparently the parts are supposed to be destroyed. But somehow they found their way into Uncle Eddy's Pik'N-Part. Time bombs waiting for unsuspecting passengers. I'm not afraid if airplanes or flying, but I m afraid of certain humans that f*ck with airplanes.

 

[phaxtris]

Some kind of corrosion inhibitor/insulator goes a long way in preventing this type of damage, this is just what happens in a seemingly innocent connection between al and stainless

@PeterT Do airplanes use stainless fasteners in the airframe ? I wouldn't have thought so given the weight of stainless, work hardening and possible corrosion issues ?

Anyways I thought it prudent to post some photographic real world evidence as there seems to be some skepticism about this topic, repairs relating to this type of corrosion are something I've delt with many times in the past...and I'm sure in the future!

 

[PeterT]

Do airplanes use stainless fasteners in the airframe ? I wouldn't have thought so given the weight of stainless, work hardening and possible corrosion issues ?

I'm just a model builder, maybe some FS guys can weigh in. I thought stainless was used but cant say where or in combination with what material. I see NAS spec all the time which relates to strength & other parameters, but links refers to some alloy compositions including stainless. Maybe the key thing is coating?

Bolts | Aircraft Spruce Canada

Aircraft Spruce Canada is a worldwide distributor of certified and homebuilt aircraft supplies.

www.aircraftspruce.ca

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www.elitefastenersinc.com

Aerospace Bolts | Military Bolts | NAS Bolt Products

www.nutsnbolts.com

 

[phaxtris]

I'm just a model builder, maybe some FS guys can weigh in. I thought stainless was used but cant say where or in combination with what material. I see NAS spec all the time which relates to strength & other parameters, but links refers to some alloy compositions including stainless. Maybe the key thing is coating?

Bolts | Aircraft Spruce Canada

Aircraft Spruce Canada is a worldwide distributor of certified and homebuilt aircraft supplies.

www.aircraftspruce.ca

SBOBET88: Situs Judi Bola SBOBET Resmi & SBOwin Terpercaya

SBOBET88 adalah situs judi bola online yang hadir sebagai penyedia taruhan sbobet lewat link alternatif sbobet mobile dan wap resmi.

www.elitefastenersinc.com

Aerospace Bolts | Military Bolts | NAS Bolt Products

www.nutsnbolts.com

i dont know either, but maybe when stainless is used a corrosion inhibitor is required by regs, and maybe required to be checked during the annual, just guesses

 

[YYCHM]

@ShawnR and @Marc Moreau should be able to comment on this.....

 

[Matt-Aburg]

Here is an example on corrosion seized components. This is the housing I am making with the shaft stuck in. It or the screws will not ever come out... This is a car part, and might have been subjected to salt. I chose to make my multicolored plastic plugs. each color represents different size or purpose. For my night shift tonight, I will clean all the swarf out of the plate, install the 3/8 dowel plugs (already made). Next will be to cut the additional C-Bores, engrave letters and numbers.. and print the multicolored plugs......

 

[phaxtris]

oh man that is a lot of tapped holes, how many hours do you figure you have in that plate ?

 

[Matt-Aburg]

oh man that is a lot of tapped holes, how many hours do you figure you have in that plate ?

Time is not relevant when retired... drilling 1350 holes was about 8 hours, thread-milling about 5 hours. Tapping was done in sessions divided over 3 days, with a cordless drill. I will be adding to my original thread later with the whole story....

 

[phaxtris]

Time is not relevant when retired... drilling 1350 holes was about 3 hours, thread-milling about 3 hours. Tapping was done in sessions divided over 3 days, with a cordless drill. I will be adding to my original thread later with the whole story....

oh thats not as bad as i thought! 6 hours split up over a few days would hardly be noticeable

 

[Matt-Aburg]

oh thats not as bad as i thought! 6 hours split up over a few days would hardly be noticeable

sorry I changed it...... Machine drilled about 8 hours max. Thread-milling 5 hours. Finish tapping was done over 3 days in 3 hour sessions, so about 9 hours manual work.

 

[phaxtris]

sorry I changed it...... Machine drilled about 8 hours max. Thread-milling 5 hours. Finish tapping was done over 3 days in 3 hour sessions, so about 9 hours manual work.

oh ok, yea thats a bit of work!

 

[ShawnR]

@ShawnR and @Marc Moreau should be able to comment on this.....

Most of the hardware is plated steel but there is a fair amount of stainless fasteners. From what I have seen, all screws are stainless, think fairings and interior panels, and bolts are plated . See excerpt below from the Aircraft Spruce link posted above

"....Hex head aircraft bolts are made of high-strength type 4037 or 8740 alloy steel (type 8740 is most commonly used). The bolts are centerless ground and threaded after heat treatment. Minimum tensile strength 125,000 PSI. Cadmium plated per specification QQ-P-416A, Type II, Class 3....."