Can you do the calcs or an fea?
350 Nm isn't all that high, but you're working with the lowest class of steel, so I wouldn't get my expectations too high...

Does it need to be partially closed like the one in the picture? Standard Crowfoot wrenches are readily available in some fairly large sizes (1/2" drive crowfoot set 1-1/16" - 2"). Even the 'flare nut' style similar to the one in your picture can be found in sizes up to 2".

Rod Smith, P.E., The artist formerly known as HotRod10

Why not just buy one that is next size smaller and modify it - machining, EDM, laser cut, water jet, plasma, etc?

Do you think it would be advisable to take a smaller size wrench and increase the opening, thus reducing the thickness of the jaws and thereby its strength, dvd?

The first thing to establish is whether the size needed really isn't available. What size is the fastener that the wrench is needed for,
Ebyate?

Rod Smith, P.E., The artist formerly known as HotRod10

Quote (bsmith)

What size is the fastener that the wrench is needed for,
Ebyate?

36mm is printed on it....

I assumed the one in the photo was an example of the type of wrench needed, but not the size. If he had one right size, why would he be trying to figure out how to fabricate one?

Rod Smith, P.E., The artist formerly known as HotRod10

it depends from the manoeuvre space : You can increase the thickness of the two lateral wings and furthermore the thickness of the plate. I do not know where you are located, but 36 mm is not so unusual

Quote (BridgeSmith)

Do you think it would be advisable to take a smaller size wrench and increase the opening, thus reducing the thickness of the jaws and thereby its strength, dvd?

Given that the size difference is not listed, I think my suggestion is reasonable. If it is a 3" opening on the "socket" and a 3-1/16" opening is needed, then maybe. Not so much if there is a big difference between the available and the desired. Too many unknowns, to not consider all avenues before ruling them out.

I wonder if OP will have the machine shop fab the wrench with the meager information he's provided so far.

Thank you all for the reply. What I require is 41mm and the particular size isnt available in the country I work. It will take atleast 3 weeks to procure it. Hence I was looking at the option to fabricate it from A36 plate.

Since you obviously need this right away, my suggestion would be to make an estimate of the wall thickness of the commercially produced tools (scaled from photos) and bump that measurement by at least 50% to account for the lower strength of the material, and give it a try. If you don't have enough clearance for that, fabricate it to fit what clearance you have, and give it a try. If it breaks and you have more clearance to work with, try again with a thicker wall. If not, you'll have to bump the thickness of the plate or acquire stronger material.

That's my suggestion, anyway. Analysis would seem to be too involved and time-consuming to be feasible (or warranted) in the situation you describe.

Rod Smith, P.E., The artist formerly known as HotRod10

Have you checked with Amazon to see what their timeframe for delivery would be? 41mm crowfoot water pump wrench,41mm crowfoot wrench.

Have you tried finding an 1-5/8" (41.275mm)? 1-5/8"crowfoot.

If you've already explored those options, I apologize.

Edit: I just set up an order from from Amazon, addressed to Kuwait City, and it showed an estimated delivery (AmazonGlobal Priority shipping) between Jan 15th and the 22nd.

Edit #2: I just realized you said you were using a 3/4" drive and you needed to apply 350Nm torque, which I had to convert to ft-lbs to get a sense of the magnitude (it's 258 ft-lbs, in case anyone is interested). So, you'd need an adapter that withstand the torque. I found one of those on Amazon, too. If you look at the Q&A, the adapter can handle that torque easily.

Rod Smith, P.E., The artist formerly known as HotRod10