Fittings: annealing, bending, hardening?

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Brian Amato
Posts: 111
Joined: Fri Aug 31, 2018 9:23 am

Fittings: annealing, bending, hardening?

Post by Brian Amato »

I think I'll start making some of the many metal fittings we need on a Piet. When I built the Corben Jr. Ace, I didn't pay too much attention to what state the metal stock was in before I bent it; I just cut it to the required width and length, stuck it in the vice and took a hammer to it until it was bent to 90degrees or 45 or what ever I needed. Didn't try to harden it either. Installed it on the airplane and called it good.
Now, I've been reading a little more. Learning about annealing before bending. Then heating to a certain temperature (or color) and then quenching to harden. For a guy who doesn't work in that field every day, it's a bit of a mystery.
What have you guys been doing...if anything...before and after you bend the various fittings we all need to make? If you tell me you've been annealing before bending and/or hardening after, please tell me what steps you've used. Thanks in advance.
Brian
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Richard Roller
Posts: 128
Joined: Mon May 22, 2017 11:14 am
Location: Olathe, Ks.

Re: Fittings: annealing, bending, hardening?

Post by Richard Roller »

Brian. Generally when you get 4130 steel it comes in the "normalized" condition. Most information on bending is listed for this condition. I recently posted a chart for bending 4130 used on 737's. The main thing is using at least the minimum bend radius recommended and being careful of the grain direction. Bending fittings in a vice with a hammer is not a good idea. The sharp edge of the vice and dings caused by the hammer will cause stress risers and possibly cracks down the road.

One more thing. The fittings usually are designed for 4130 in the normalized condition. It would be noted if it needed to be hardened.
Brian Amato
Posts: 111
Joined: Fri Aug 31, 2018 9:23 am

Re: Fittings: annealing, bending, hardening?

Post by Brian Amato »

Thanks for that nice reply.
No....when I said "stick it in the vise and hammer away" I'm really more careful than that. I put soft jaws in my vice with built-in radiused corners.
Stress risers: Yup, I'm aware of them too.
Grain direction: bend perpendicular to the grain, am I right...not WITH the grain or it can crack like wood grain?
So, if it's "normalized" to begin with, no need to anneal it before I bend or heat treat it after I bend. Thanks. College metallurgy was a lot of years ago.
I'm off to the shop :)
tom kreiner
Posts: 62
Joined: Sat Feb 25, 2017 9:49 am

Re: Fittings: annealing, bending, hardening?

Post by tom kreiner »

Another item regarding metal work, is to draw file edges and then sand smooth with emery cloth to eliminate ALL defects on edges of piece, as these, too, will create create crack propagation points.

This type of prep must be done prior to bending.
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