Air Gun Home :: View topic - Metal Hardness and source for thread adapters?

AirGunEric · Site Admin

I need to either find a thread adapter of an obscure setup:

1/8" NPT Female to 7/16-20 Left-Hand thread Female. Anyone know of a good source for this sort of thing?

And next, if I have to make my own adapter:

If I pick a common Brass alloy, say one rated at a Rockwell Hardness of B77- what iron or steel product is it comparable to in respect to tapping it? For example, I've drilled and tapped "plain" steel and created my own "bolts" using a blank rod (3/8") (the end result of which might have been able to be classified as a "Grade 5" fastener). How would brass compare to this- a heck of a lot easier, about the same, or much more difficult? I'd assume easier- but I hate assuming things.

Alstone · Moderator & Site Supporter

Hi Eric
I assume all you want is a piece of tube with 3/8 NPT at one end and 7/16 x20 LH UNF at the other, the easy way to do this is to get a nut for each size and braze them together.

If you want to go down the tapping route then I would suggest using brass as it will tap easily with a tap made out of a old bolt, especialy if you case harden the bolt and anneal the brass, it will not be as strong as steel but it dependes on what you are using it for, you can tap steel with home made taps but they need to be made fron high carbon steel so as they can be hardened prolerly.
If you are using the adapter for high pressure gas use steel or bronze.

Have fun.
AL

AirGunEric · Site Admin

Hmmm- don't know why I didn't think of sticking two nuts together- 1/8" NPT and 7/16-20 LH LNF. Of course- I have to find a LH LNF nut...

But- that's probably going to be the easiest and quickest route for me. I'm actually using an extra Crosman AirSource adapter in pieces to construct a basic feed tube (using the AS tube and spacer) to attach a standard 1/8" NPT paintball-tank hose. Unfortunately- the outer end of the Crosman tube has that funky 7/16" male end on it. But- using the Crosman pieces and a couple of steel nuts isn't likely to weigh more than a pound (vs. the 2-3 pounds a complete Crosman AirSource setup weighs) and it won't block the rifle's forearm.

All of this is for Co2. Just out of curiosity more than anything- brass wouldn't be able to handle 8-900psi without fracturing? I have no idea- I assumed it could (with 'tensile' strenths of 60,000 psi I assume a 900psi pressure load was a no-brainer, oh well).

Alstone · Moderator & Site Supporter

Brass would be Ok for Co2, but for PCP you would need a brass alloy to overcome the brittleness of ordinary Brass, it's not so much the hardness of brass that makes the diffrence but the brittleness ( it can crack off easily) and you would not want an air bottle flying round with 3000psi trying to get out. Or maybe you would! then you could Crony it?. HaHa 2000fps missile launcher.

AL

Alstone · Moderator & Site Supporter

further to the above if you can get two decent brass nuts you could solder them together using silver solder use 60% silver rods and a good flux.

this will cope with co2 no problem and you will get a better weld than brazing.

Silver solder is sold in all good model shops, before you ask

AL