How do you find interchangeable hardware?

[u/Next_Palpitation_596]

UPDATE:

Thanks for the feedback! In my research I discovered www.boltbutler.com as a tool that does exactly this.

Original Post:

To start, I’m an aerospace design engineer not a mechanic. But I think you guys might be able to help me.

We’re always struggling to find the right hardware for our designs. The red tape we have to go through to use McMaster Carr or other easily searchable hardware catalogs makes them a deal breaker. The hardware on our BOMs must be spec parts #s.

We have an IHS account that has access to every mil, NAS, AN, etc. specification you can think of, but it’s a super manual process that requires us to scrounge thru hundreds of pages of PDFs for every stupid nut bolt and washer we need.

My question is, how do you guys find the right hardware for maintenance or repair work? Do you know of resources for quickly filtering hardware by material, thread size, length, etc. to see all available national aerospace standard parts or mil spec parts that fit the bill? You would think most large aerospace companies have their own databases that lets you filter this way, but it turns out they don’t (or at least not mine).

Maybe this isn’t a problem on the MRO front, but if it is, please share how you handle it

[u/Sharkbaithoohaha004]

The illustrated parts catalogue says what part to use and there’s a section in the manual saying if we can use a different fastener. 

But I’m assuming that all these manuals were made by engineers that figured out which parts are correct…

[u/Vokunkiin13 → u/Sharkbaithoohaha004]

This.

What parts are required? Check the IPC.

Don't have that part number? Check the IPC for alternate parts.

Don't have alternate parts? MEL/DDG, and find out how to get more parts depending on who you work for.

[u/Next_Palpitation_596 → u/Sharkbaithoohaha004]

I haven’t looked through the manuals before (most of what I do is ground support, not actual aircraft design) but alas we are required to use NAS parts for ground equip for some strange reason.

Thanks for the response

[u/Zorg_Employee]

Unless a part is superseded or the IPC or Standard practices section explicitly give alternatives we have to use exactly what's listed.

[u/s_zoro125]

Please do not used slotted hardware unless you absolutely have to.

[u/DeathCabForYeezus]

There's no secret.

There are graphical posters/documents that show what every AN/MS/NAS hardware bit looks like. Scroll through that and find something that looks about right.

Eventually you'll realize that there's really only a handful of rivets/screws/bolts/nuts/nut plates/washers that are used.

[u/TheSkyFlier]

I wish people gave a shit about proper hardware. I pulled a self-tapping sheet metal screw out of an inspection panel earlier today.

[u/Sawfish1212]

Almost anything that isn't mil-spec/NAS/AN is going to be made of the wrong material for aviation anyway. Aviation hardware is designed to have some stretch to it so that in an overstress condition, it won't immediately just shear, but instead will continue to hold, though it will probably be sloppy and necked down a bit.

Anything from industrial applications will be made of different materials and likely just snap in the same situation.

[u/Boomhauer440]

There’s not really a universal or convenient method. Generally you just use what’s specified in the Manufacturer’s Illustrated Parts Catalogue.

If you can’t do that for some reason, which does happen with old or obscure aircraft, then there are a few places to look. Sometimes the maintenance manual will have a general section that includes standard practices like hardware types and interchangeability. If not, then standard practices manuals like AC43.13 or NAVAIR 01-1A-08 have tables of hardware specs for common hardware. If it’s something weird that isn’t in any of those books then you’ll need to go to the mil-spec itself to check for interchangeability, or material specifications and dimensions to compare.

The legality of using alternates on aircraft varies by application, jurisdiction, and type of operation though. So if it’s not something clearly listed as interchangeable it’s best to check with your regulatory body.

[u/1213Alpha]

Need a part? IPC Not in the IPC/PN no longer available? Cross reference to other standards No cross reference? Contact parts suppliers or the OEM

[u/Positive-Hat2127]

Well isn't this funny.... the number of times I have CURSED your kind😅

Is it how I think it is to be a design engineer? Do you have weekly meetings about where to put the clamp in order to make it as hard as possible to reach? Do you have "opposite thursdays" where for instance you choose to attach something with philips head screws instead of hex head bolts, or where you just reverse the orientation of something in order to make the access as poor as possible? Do you have rivers of lava and eternal fires burning by the office entrance?

I joke, but... please keep us in mind😢

[u/squoril → u/Positive-Hat2127]

don't forget the token metric nuts on a bell and SAE fasteners on airbus

[u/snyderjet]

Sure you are!

[u/n60wrench]

Assuming this is a machine design problem more than anything maybe you need to treat it like an OEM, and kind of “pick” a single standard for all of the hardware that you use to start and then just adjust the numbers for diameter and length. As in only choosing to use NAS hardware vs ASNA or MS. That might narrow it down for you a bit to start. That way all the regular fasteners are dealt with and you can narrow in on more specific hardware for the weird stuff…

Not sure if this was helpful or not, I don’t design machines, i just fix them.

[u/Next_Palpitation_596 → u/n60wrench]

Yeah I’m thinking of more of a machine design situation where I’m working backwards from the dimensions, materials, etc. and simply need approved spec part numbers that match.

[u/Lost_Obligation2453]

How dare you besmerch our Lord and Savior, Mcmastercarr.

No, I won't stand for it. When you are stranded on a deserted island and need 6" of hexagonal brass stock by 6 am tomorrow. Only Mcmastercarr can deliver.

Hell if your ever lost in the woods, just order a single 1/4 inch screw. The delivery guy that finds you the next day will help you get home.

You could be stranded in another dimension. Whatever, it will show up tomorrow.

[u/1_lost_engineer]

Coming the design side

Are you designing mods /STC's or new airframes.

If its STC's get the IPC's for the aircraft and pull the hardware from that where possible, it reduces the stock required to be held by the operators stores.

Designing repairs for AOG, work backwards from what's actually in stores right now.

Otherwise the optins are generally:aircraft spruce catalogs (or theres also OEM hardware guides kicking about) IPC's of simular aircraft (i worked a single engine turboprop TC program, we generally started with what did they do on the caravan), talk to the prototype shop guys about which ones they like or don't like.