https://www.speedwaymotors.com/Straight-3-8-Inch-24-IFF-to-1-8-Inch-NPT-Male-Adapter,6463.html?sku=91031831&utm_medium=CSEGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE&gclid=CjwKCAjwpKCDBhBPEiwAFgBzj1iPXBha8J-9Arbcs0BpWGdeq4lIdlk0Z5hehzR4tDDCstv3sbNk-hoCDb8QAvD_BwEnot sure this would clear everything
It might not be difficult to put a flat in them. If they didn't seal, do you think that epoxy would be sufficient to seal? Cheap enough to sacrifice. I ordered three from ebay for $12 shipped.
Fwiw, I have some of the brass brake adapters (used). They are cut for flare. I threw one in the lathe and squared the bottom with a 5/16” endmill. Pictures below show the results. If you can see past the glare (I’m no photographer), you can see the mark made by the bd. The one screwed in is ninja brand. The other one pictured is a China brand. The ninja offers more thread engagement but the China gets plenty. Hth,Dave
The ones I received from ebay, today, are the same part number/brand as the speedway ones linked above. They are brass. I measured 0.090" if the flare is machined flat to where it starts to neck down from hex to 1/8 npt. The female threads to the outside hex at the thinnest point are 0.052" The through hole is 0.127" vs 0.119" for the inner part of the burst disk. The feed hole to burst disk is smaller on bottle regulators, but think there are ways to make that smaller. I suspect the smaller hole on regs, is to limit flow when burst. To use this with the flex reg, protecting to 3K, would use a 5k burst disk. While this is for hydraulic applications, don't know if it is strong enough. Thoughts on that?I'll machine the flare flat and see if I can get burst disk to seal. I'm willing to test with a 1.8k, but not sure of blowing a 5k.