Metric hardware.

[TwoDeadDogs]

Hello all
Re:metric hardware.Is the stuff interchangeable between aircraft in the same fashion as AN/MS/NAS is across Imperial-fitted aircraft? Can I,for instance,take an 8mm bolt from a Squirrel and fit it to a Puma? Or,do the manufacturers of metric aircraft number the bolts so that they are unique to each type?
regards
TDD

[Lu Zuckerman]

If the part number or standard number are the same for different applications on different aircraft then the hardware should be interchangeable. However if the item has a special number then it should only be used in that particular application. Some times in US standards you will have a common bolt but the head is painted green. That means it was checked for cracks and inclusions and although it has a common number it can only be used in that specific application. If you have a high shear or close tolerance bolt it will have a different part number from bolts of the same size. The same should be true for other hardware items.

I will end this message with the caveat, I think.

Based on the following post, I should have kept my mouth shut. However based on the following post you guys have to work to a terrible system. Hopefully it is never adopted in the US.

------------------
The Cat

[This message has been edited by Lu Zuckerman (edited 05 March 2001).]

[Genghis the Engineer]

Be very very careful. I say this for several reasons: -

(1) There are several metric bolt standards, those which you're most likely to meet are "8.8" (which is the most likely on an aircraft) or "10.9" (which is more brittle, but occasionally used in a few aircraft applications).

(2) These standards are based upon the material specification alone, and not the quality.

(3) It was a French idea!

One GA manufacturer of my acquaintance, buys 8.8 bolts for a great many applications - but it then has them cadmium plated, de-embrittled, and then batch tests them to destruction. Finally, they get issued with a CofC. The problem is that the head markings are the same, and after a hundred hours on the aircraft you can't see the surface differences between that and an unmodified bolt.

Another uses standard 8.8 bolts, with only a visual inspection, but then puts a very low hours life on them.

I recently saw some new bolts which *I think* were from the Ukraine (Antonov and their many offshoots), and were interchangeable with standard 8.8 hardware but obviously of an equivalent standard to AN.

So, in summary metric bolts are a minefield, and I'd be very careful, even if the head markings match up - two apparently identical bolts may well not be.

G

[Genghis the Engineer]

And another thing....

Renault truck windscreen wipers are interchangeable with the Puma's.

The door catches from a Gazellecopter are from a Renault 5.

G

[Lu Zuckerman]

To: Genghis

The constant velocity joint used in the Sikorsky S 51 tail rotor drive system was repackaged in a stainless steel container but the insides came off of a US Army 6 X 6 truck. The US Army ordered 1000s of bearings that were not aircraft standard and installed them in the tail rotor drive shafts of Sikorsky H-19s. The correct bearings had the same federal stock number of a bearing used on army vehicles. Needless to say, they didn’t hold up very long.

------------------
The Cat

[This message has been edited by Lu Zuckerman (edited 06 March 2001).]

[Golden Rivet]

Ever heard of the manufacturers illustrated parts catalogue!!!!

------------------
Fools rush in where Angels fear to tread

[TwoDeadDogs]

Thanx to all for your replies.
GR,piss off! Of course,I've heard of IPCs.My point is;can metric hardware be exchanged(in non-specific situations)across metric aircraft,e.g;an operator having Aerospatiale/Eurocopter types or an operator having Airbus types.When I was trained,we recieved virtually no gen on Metric hardware,whereas we got loads of gen on US stuff and a little on UK stuff.There does not seem to be an equivalent book out there for metric stuff,in the same fashion as the APs/CAIPs.I do some work on Permit types and am coming into contact with metric stuff more often and I could really use the gen.
thanx again
TDD
PS: remember the Ford Motorcraft voltage regulators on 172s?

[Blacksheep]

Yes, I see where you're coming from Dogs,

We all know about AN, MS, MIL and NAS specs and an AN960 is an AN960 is an AN960 and so on...
but where DO we find the equivalent for metric? It's a bit of a dark area.

**********************************
Through difficulties to the cinema

[Genghis the Engineer]

Basis for standard metric thread lengths is..

<= 125mm nominal length; length of thread 2d+6mm
125 - 200mm; length of thread 2d+12mm
200mm+; length of thread 2d+25mm
(d=nominal diameter)

Bolts are specified as x.y, where...

x = 1/10 minimum tensile strength in kgf/mm²
y = 1/10 ratio of stress at permanent set limit to minimum tensile strength x 100

So an 8.8 bolt has 80 kgf/mm² minimum strength, and (1/10)x(64/80)x100 = 8 second digit.

Or a 10.9 bolt has 100/mm² minimum strength and (1/10)x(90/100)x100 = 9 second digit.

Multiplying the two numbers gives the stress at the permanent set limit, otherwise known as the yield stress. So, the yield stress on a 10.9 bolt is 90 kgf/mm².

The specifying standard is ISO/DR911 for bolts.


For nuts, the strength grade is a single number, and it's a tenth of the proof load stress in kg/mm². So a grade 12 nut has a proof load stress is 120 kgf/mm². This is in BS3692.

The recommended matching of nuts to bolt is...

Bolt Nut
4.6 4
4.8 4
5.6 5
5.8 5
6.6 6
6.8 6
8.8 8
10.9 12
12.9 12
14.9 14

There's also a range of Vickers hardenesses permitted for the ranges of bolts, specifically: -

4.8 110 - 170
5.8 140 - 215
6.8 170 - 245
8.8 225 - 300
10.9 250 - 370
12.9 330 - 440
14.9 400 - 510

Hope this helps, but none of it changes what I said before, take care!

G

[innocent bystander]

gengis, have u been reading books,i'm impressed, i wonder if the french have the same problems with an spec bolts? i can only just spell metric,

[Golden Rivet]

Sorry, sarchasm got the better of me there.
Point I was trying to make was that this particular area is such a minefield that your only option is to use the IPC.

------------------
Fools rush in where Angels fear to tread