SP G250 jam nut

[rsingler]

First, I'm good for a dozen nuts to start.

But... don't shoot the messenger.
I think we need to decide whether you want this nut to be just a G250 nut, or have wider application.

As you know the G250V, G260, and R- and S-series have that little land for a sealing o-ring between the barrel nut and the B-nut for the hose. The G250 does not.

As you can see below, the Atomic .437" nut fits fine on an S-series spindle, and the tall nut fits fine on a G260 barrel:

But the distance from the reg body to the land is different between the two regs.
G250V & G260 have longer run, while R- and S-series have shorter run.

That means, if we use an Atomic nut, or an even shorter 0.425" nut, threads will protrude from the nut before the land.
G260:

G250V:

 

[Couv]

Are those turret nuts for the MK10?

No, those are for MK5s

 

[rsingler]

If we just want to cover G250 and R, S-series, we could go with a 0.425" nut.

We might consider a washer or washers to increase our applicability. It's already done in plastic in the R-series:

And in metal in other Scubapro regs:

Atomic does it too.

It's just a thought, but we could use a 0.380 - 0.400" nut with a 0.1" washer to get the best of both worlds.

Of course, that also means considering a small chamfer to accept that oring, which may increase mfg cost.

I'm open to whatever y'all recommend, and what Bryan is willing to consider. Just wanted to raise the issue, in the interest of full disclosure.

 

[Bryan@Vintage Double Hose]

I just bought two more turret nuts!

MK 10's don't need their turret bolts replaced.

 

[Couv]

I'm open to whatever y'all recommend, and what Bryan is willing to consider. Just wanted to raise the issue, in the interest of full disclosure.

Rob, is there a reason a 0.500 would not work on all the regs you measured?

 

[rsingler]

Rob, is there a reason a 0.500 would not work on all the regs you measured?

A .500" nut on a G250 leaves only about 1mm of hose oring engagement before the B-nut hits the jam nut. I'd be afraid the hose wouldn't seal to the regulator reliably.

A 0.500" nut on an R295 is even worse.

 

[rsingler]

There is a chamfer in both regs' barrels. That creates a ramp that effectively wastes the first 1mm of hose nut engagement, before the oring dives into the barrel.

And the oring is another couple of mm's inside the hose. So I'm thinking you need about 4-5 threads to be sure of a connection. I may be wrong.

 

[Couv]

I'm thinking you need about 4-5 threads to be sure of a connection. I may be wrong.

I just checked on a real second stage (BA) and it takes almost two full turns of the hose B-nut before a seal is made. Total turns before final torque was 4 1/2. That brings us to the question of what would be the maximum length of the jam nut that will allow at least 4 turns of the B-nut before hitting the jam nut?

 

[Couv]

MK 10's don't need their turret bolts replaced.

Au contraire, mon frere. MK10 turret retainers have been known to sheer. Here is one from a "good deal" I got. Note it is made of brass, so it must have come from an early one.

 

[Bryan@Vintage Double Hose]

Au contraire, mon frere. MK10 turret retainers have been known to sheer. Here is one from a "good deal" I got. Note it is made of brass, so it must have come from an early one.
View attachment 454169

I learn something new every day....Never seen a brass one before. Tks Coonass.