Metric bolt source

These are obviously AN3 bolts, 3/16 inch diameter (4.8 mm) and marked with an “X”. Certainly not metric. M5 has 5.0 mm shank, although the threads are almost identical to AN3.

It would be interesting to know what these bolts are used for.

Honestly I would not give a sh** for getting imperial screws for that purpose. That size cannot possibly be a critical function in an aircraft. So instead I´d run a M 5 tap through the female tread in case no nut is on the other end. I did this in other uses as M 5 is extremely close to that 3/16 " size and fits nicely. Check the pitch and report here about my flawed thinking . . . Vic

vic wrote:

That size cannot possibly be a critical function in an aircraft.

Well, maybe, maybe not. I have certainly seen, used, and indeed approved, the use of non aircraft fasteners in non critical applications in an airplane. That said, a greater issue may become that the next maintainer of the airplane finds a non approved fastener substitution, then wonders what else has been “done to” this airplane, and delves into it. I have seen this (and done this) many times. When I see good, consistent workmanship, it builds my confidence in the dedication of the maintainer and owner, and work can progress with less distraction.

In that case use proper sourced nuts and bolts – please You can get everything from ICP, reasonably priced and shipped directly from Italy. The Savannah is designed and built cording to ASTM F2245. IMO Aicraft Spruce will do just fine also.

Peter wrote:

The locknut is nylon so it probably isn’t that critical.

Means absolutely nothing. Cotter pins and similar, are only necessary when the bolt is holding together individually rotating parts, like hinges for instance, or for vibrating parts (but wire is usually a better option). For structural parts where correct torque is important, nylon lock nuts are not even necessary, but used because they require no further inspection later (they won’t unscrew themselves).

LeSving wrote:

You can get everything from ICP, reasonably priced

Very true. I ordered the 1000hr kit, it contained all bolts, nuts, aluminium parts for hinges, aluminum parts for front suspension, wheel bearings and axles, bungee, engine hoses etc. etc – the cost was around 1500EUR.

it’s still a standard AN bolt, K P is the manufacturer markings

As is ‘AFC’ on the first one. The X is what matters.

My first stop for an AN3 bolts plus nuts/washers like this would be the parts store on the field. However if I wanted to save time I’d order them on my phone before leaving the hangar. To get the correct part number this info may be useful.

4.8/25.4 = 3/16 => AN3