Flared aircraft lightening holes

In actual fact, it reduces the propensity to form a crack from the thin cut edge. It reduces the chance of vibrations flexing the original thin flat plate at that point and thus causing fatigue cracks through the vibration. The flange, in effect, does stiffen it to reduce the flexibility.

We are also being very loose with terminology. As the flange is perpendicular to the plane of the platework, it is effectively increasing the thickness of the component and stiffening it around two of the axes at the expense of the third. In fact, as we are into the ‘breadth times depth cubed’ bit of elasticity, you get a huge increase in stiffness around these for not much loss on the other.

Richard

In actual fact, it reduces the propensity to form a crack from the thin cut edge. It reduces the chance of vibrations flexing the original thin flat plate at that point and thus causing fatigue cracks through the vibration. The flange, in effect, does stiffen it to reduce the flexibility.

How does the lightning know how to go through the holes?

Oh, is that my coat?

Richard

:p

A lightening hole definitely lightens a part as you are removing material.

Adding a flange around the hole edge merely stiffens (stabilises) the edge of the hole.

Yes because it takes the bit out of the middle and strengthens at the same time!

I would suggest it lightens and stiffens, not strengthens. the strength comes from the flanges around the Spar, rib, what have you.

Yes because it takes the bit out of the middle and strengthens at the same time!

Do they actually lighten?

Just remembered -the Frost one is just the flaring tool – you will need the matching hole cutters.

Thanks for taking the time to dig the info out chaps. Much appreciated but the cutting tool only does straight edge flares, really after a rounded finish as per British aircraft.

The Frost one looks promising, thanks

Frost Restoration sell them too:

I have several and they work well.

http://www.frost.co.uk/hole-flares.html

http://www.aircraftspruce.com/catalog/topages/flanging360.php

Worth a look?

Hi Ken, that would be great if you could, I’m after a 1 3/4″ (2″ would suffice) 4″ and 5″.

Thanks

Supermarine aero engineering in Stoke have some large home made ones that I have used a few times, not sure of the exact sizes but up to 6″ from memory. I could ask for you if you let me know the exact sizes
Ken

Thanks Tony, I’d seen these ones before but I need up to 5″ diameter. Was hoping to avoid making a tool but it seems like the only option.

Much appreciated.

If you are not into doing many a male/female pair or forming tools made from wood will suffice, just clamping them in the vice will do if the item being flanged is small, if it bigger then a flypress is needed.

Richard

here’s one:

item no.190084073925
and another

230743124926
I buy hole punch and flare them

The dies to make them are not incredibly difficult and would be well within the capability of most toolmakers.

They’re usually called flanged lightening holes if that helps.

Thanks chaps, any ideas what they are called? I’ve googled the full works….. Flange, Swage, Flared, Dimples, Dies, Presses but still no luck 😡

You can get a tool which, on one side will cut the hole, and on the other, will flange it.

Bruce