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Discussion in 'General Experimental Aviation Questions' started by mountainman, Jan 18, 2020.
does AN hardware exceed grade 8 hardware ?
Both specs are online. Knock yourself out.
The really big advantages in AN hardware over Grade 8 is not that they are stronger under tensile loading, but:
Many more lengths available to match need closely;
Come drilled for safety wire in either the head or the shank or both or none, as you select;
Have more length at full diameter for more strength in shear;
Better cleanliness spec for steel (improves fatigue);
Strength range is usually smaller and min part strength can be higher;
Anti-corrosion is always supplied;
More inherent QC.
Yeah, I know, in Grade 8 you can get whatever length of straight shaft or threads; Drilled spots; Cleanliness spec; Anticorrosion treatment; QC support. All you have to do is specify them and then pay for them. They are unlikely to have the fastener you need on the shelf. Custom runs to suit cost more and usually have min runs, like 1000 or 10,000. In short, to get a better all around fastener in Grade 8, you gotta spec it up and make sure that the supplier delivers to the spec.
Much easier to just buy AN per your needs and be happy.
The nominal strength of grade 8 bolts is higher than AN bolts, which are closer to grade 5. However, with the higher strength can come brittleness; a grade 8 bolt may snap where a grade 5 (or AN) bolt will bend. But even more important is that AN bolts have much better quality control and have other advantages as Billski listed.
FWIW, the early (and maybe later, I don't know) Quicksilver ultralights used mostly AN bolts but also used grade 5 bolts in a few spots where they were threaded into aluminum (aluminum doesn't like fine threads, which AN bolts are, grade 5 bolts come in both fine and coarse). Quicksilver was adamant that grade 8 bolts NOT be used there.
AN bolts will bend and generally still bring you back home when they are overstressed.....unlike a grade 8 bolt that will just break and then you're S-O-L wherever it happens.
I owned and was CEO of a Aerospace hardware distribution corporation...In my experience there is no way to really compare the two. The grade 8 hardware is inferior to Mil spec hardware in almost every application and certainly should not be used in an aircraft.. To summarize some of what has already been said... AN bolts are made from good alloy steel and basically derive their strength from that fact. They are produced under strict quality control and each lot has to be certified to the AN and Mil-spec and sample tested to comply.. You can check out the specs here..( http://everyspec.com/AN-SPECS/AN100-AN999/AN3_THRU_AN20_REV-12_6281/ ) Plated AN bolts are plated to the QQP- 416 spec which requires them to be baked at 400 degrees within 4 hours of being plated to relieve hydrogen embrittlement caused by the electroplating process... You can check out that spec here. ( http://everyspec.com/FED_SPECS/Q/QQ-P-416F_22867 ) Grade eight bolts are made from medium carbon steel and are case hardened to achieve their rated tensile and shear strength ... Quality control is no where near as stringent and the case hardening makes them brittle and subject to breaking due to vibration and other like factors. With out going into a lot of detail there is simply no comparison between the two and as far as practical applications go each has their own place. The AN bolt is far more ductile because of the better quality steel, They will stretch and bend considerably before failure.. This was stated earlier as well but If you want a bolt that will bring you home and back to the ground safely use an AN, MS or NAS bolt. There are Grade eight bolts that can be found in the Mil-specs but they are used in ground handling equipment, surface vehicles and like equipment. If you are looking for a particular AN bolt and are having trouble finding it message me I might be able to help you out.
Grade 8 hardware is being used in some aircraft, Tecnam is one I know. BUT they do used AN hardware in critical areas like wing attachment, wing struts, engine mount etc. The difficulty with grade 8 or any commercial hardware is that there is a lot of rubbish available. If you do use this hardware, make sure it is from a reputable manufacturer. A good source are Caterpillar and Komatsu with their own brands and QC.
Are they actual commercial Grade 8 or European aerospace grade 8 metric, it starts to get messy once you add in European GA aircraft / Rotorcraft (the bolts come in the same horrible large steps in length as commercial hardware).
Another thing is what torque setting to use, different surface finish, different torque.
If one was to use commercial hardware, one should probably break a sample from each lot brought (should really do it on aerospace stuff as well per the AD / SAIB).
I did a short stint in Subsea Oil & Gas and all the bolts had to be traceable and from a European or American manufacture.
Locally about a decade ago an aircraft nearly lost the engine (3 out of 4 bolts failed, engine retained by cowl which it was designed to do) and it was found that the MS bolts in the engine mount had been made from carbon steel and Heat treated to get the strength requirements of the MS spec (but not the yield).
In most of the world AN hardware is non existent making automotive bolts attractive.Impression is given that Automotive hardware is junk without quality.It is dubbed as Commercial Hardware store variety.Does Toyota make junk bolts ?
A minimax ultralight has about 2100 Lbs of lift force through the struts which is fed into a 1 inch steel tube through a 1/4 bolt in double shear. A 1/4" grade 2 steel bolt can take 2000lbs in single shear or twice in double.A grade5 bolt can take 3500lbs.
It seems if you can get an actual Grade5 or 8.8 metric bolt it can handle the loads .One can always go one size higher for a little weight penalty.
JWP i have been searching for 5/16 x 1 1/14 socket head bolts for a prop adapter to mount power fin prop to my mosler flange having no luck with AN hardware any help would be nice thank you
I agree except that I don't believe common AN bolts need to be baked after plating.
MS16998-60 5/16-24 x 1 1/4 (superseded by NAS1351)
MS16997-81 5/16-18 x 1 1/4 (superseded by NAS1352)
Does it need to be a socket head screw or would a standard AN bolt fit?
But... what Mosler? If it's the 2 cylinder, nothing but a fixed putch wood prop should be used, adjustable props reportedly can't handle the single power pulse per revolution. By comparison, a two cylinder 2-stroke with a 2.5:1 redrive is making five power pulses per revolution, much smoother running.
Powerfins are typically used on Rotax 2-strokes, which use metric grade 8.8 (comparable in strength to US grade 5 or AN) hardware (8mm is very close to 5/16).
Having been a power train engineer at both Ford and FIAT-Chrysler, I can tell you that every bolted connection in the vehicle is engineered. Fasteners from internal specs, for hardness, strength, ductility, cleanliness, fatigue, corrosion resistence and quality control. These specs include SAE grade 8, but go beyond because Grade 8 by itself is usually not enough. Then all of the joints get specs for how they are torqued and the joints are analyzed and tested in the fastener lab. Almost all of them are applied by DC nutrunners. Some are torqued, some run to torque plus angle, some are run to yield, and it is all done based upon the joints. This goes beyond engines and transmissions, to axles, suspensions, wheel and brakes, seat mounts, restraints, instrument panels...
You do not get that level of engineering in your airplane joints and from bolts that may meet Grade 8 and may or may not be up to all of the other issues. If you want to use an SAE Grade 5 or 8 bolt in an application where an AN bolt is normally used, to be safe, you have to do all of the joint analysis for strength, fatigue, corrosion, overload, torque process, etc to make sure that it is at least even on all counts as the AN bolt.
This is no difference from any other place where someone wants to change an existing design - you are becoming the designer of a new airplane. Build it to the plans and you know that you will get the demonstrated airplane, warts and all, but still the demonstrated airplane. Make significant changes (swapping bolt grades are a significant change) and you are designing a new airplane with new capabilities. Some of those new capabilities may be less than the original, and that can be bad indeed.
But... what Mosler? If it's the 2 cylinder, nothing but a fixed putch wood prop should be used, adjustable props reportedly can't handle the single power pulse per
revolution. By comparison, a two cylinder 2-stroke with a 2.5:1 redrive is making five power pulses per revolution, much smoother running.
Read this. http://www.greatplainsas.com/phubhistory.html
i think i will return power fin prop but i see tennesee props has closed its doors any sugestions
Culver, Performance Propeller, Sterba, Prince. Frank at Performance Propeller is widely regarded as the "go to" guy for half VW props. Half VWs need a skinny prop so they can spin up to the rpm where they're making the power.
I got four props with my CB40 powered Fisher, the one that worked the best was a Catto 56x27.5 (I believe Catto no longer makes small wood props).
How much of “working best” do you attribute to the Catto design verses just a better match of diameter and pitch?
The standard for metric screws is a standard on how to specify screws, nuts and on. I do think there is some tables on preferred/recommended sizes or size and proportion. But the ISO metric screw standard is no specification of screws like the AN system with its tabulated sizes for a selection of screws. On the other side, any AN screw could be specified within the ISO standard framework.
No idea, really, but most likely pitch, there was nothing special about the Catto prop, it was a typical wood prop shape.
My understanding about grade 8 and grade 5 bolts
is that they use the same steel,and that grade 5 are
A rule of thumb for designing would be to use the toughest hardware availible, and only use the harder stuff where you need it for shear streangth or wear,the last would be hopefully not a consideration in aircraft use.
As to the original question, yes aircraft hardware exceeds grade 8, as would grade 5.
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