Advice re: Scubapro Mk5 or Mk10 DIN conversion

[agilis]

The washers are INSIDE the reg, there should be no salt water there. Just air at 200 bars...
And the interior of the reg is brass NOT chromed, too, as you see here :

View attachment 566840

So it will be "brass over brass", and no risk of more corrosion than what already happens there...

Here you see the stainless steel washers inside the hole:

View attachment 566841

They fit perfectly. However, they are slightly too thick, I would prefer to use exactly the minimum thickness required, for ensuring that the barrel is screwed with the largest number of threads possible.

Couv, your document was very useful, as it did proof that the Trident A166 is an exact copy of the Scubapro kit # 10.400.030, which was the old kit for MK9, MK10, MK15.
The MK5 instead was requiring the kit # 10.105.030, which has a much longer barrel, with the O-ring in a groove just after the threads.

I dug out the new unused Scubapro DIN conversion kit for the Mk V that I have had for decades. The paperwork with it lists two 'p/n' numbers, with a check off box for each: p/n 10.105.030 (MK5), and p/n 10.043.030 (MK2,MK3). The MK5 box is checked. There is very little else written, except a warning that working pressure is not to exceed 3300 psi. The brass knob looks like your Trident, except the checkering is slightly larger. I'm thinking of finally installing it on one of my Mk 5s after all these years. Other than replacing the ancient O ring above the threads it looks good to go.

 

[Angelo Farina]

I dug out the new unused Scubapro DIN conversion kit for the Mk V that I have had for decades. The paperwork with it lists two 'p/n' numbers, with a check off box for each: p/n 10.105.030 (MK5), and p/n 10.043.030 (MK2,MK3). The MK5 box is checked. There is very little else written, except a warning that working pressure is not to exceed 3300 psi. The brass knob looks like your Trident, except the checkering is slightly larger. I thinking of finally installing it on one of my Mk 5s after all these years. Other than replacing the ancient O ring above the threads it looks good to go.

If you change your mind, I would be more than happy to buy that vintage SP kit!
Can you post some photos of the parts? I have never touched one original in person...

 

[Umuntu]

In the following photos you see my experiments trying to fit these kits on my MK5, preserving the saddle, placing the O-ring in the small groove at the end of the threaded part (instead of inside the larger groove behind, as I did on the MK10), and using a couple of stainless-steel 1.2mm washers.
I ordered brass washer with a thickness of 1mm, when they arrive I will decide which are better (but with these ones, being thicker, the saddle does not lock the knob).

View attachment 566801
The barrel contained in the Scubapro universal kit vs. the original joke nut.

I noticed in your picture comparing the new DIN retainer barrel with the old Yoke retainer barrel that you have the revised DIN SP retainer with a shorter thread section and a shoulder designed to prevent the threads "bottoming out" in the MK20 and MK25. See the attached document.

Does the revised DIN retainer still cause a bottoming out in the MK5 body without the brass washers?

 

[Perryed]

I noticed in your picture comparing the new DIN retainer barrel with the old Yoke retainer barrel that you have the revised DIN SP retainer with a shorter thread section and a shoulder designed to prevent the threads "bottoming out" in the MK20 and MK25. See the attached document.

Does the revised DIN retainer still cause a bottoming out in the MK5 body without the brass washers?

Isn`t this the modification that prevents the regulator body from cracking and exploding if the retainer is over torqued on the MK20`s. ?

 

[Angelo Farina]

I noticed in your picture comparing the new DIN retainer barrel with the old Yoke retainer barrel that you have the revised DIN SP retainer with a shorter thread section and a shoulder designed to prevent the threads "bottoming out" in the MK20 and MK25. See the attached document.

Does the revised DIN retainer still cause a bottoming out in the MK5 body without the brass washers?

The new DIN retainer does bottom out in the MK5 body. The brass ring remains in the zone where the O-ring seals, it does not arrive to the conical chamfer between the thread and the cylindrical sealing zone.
However also the original yoke nut bottoms out in the MK5. This reg seems designed for this to occur.
It is the MK20 where the nut must not be screwed in too much...

 

[Umuntu]

The new DIN retainer does bottom out in the MK5 body. The brass ring remains in the zone where the O-ring seals, it does not arrive to the conical chamfer between the thread and the cylindrical sealing zone.
However also the original yoke nut bottoms out in the MK5. This reg seems designed for this to occur.
It is the MK20 where the nut must not be screwed in too much...

In both the MK20 and earlier MK25 retainers the threaded tip to shoulder was too long for the depth of the threaded inlet on the regulator body. This caused cracking of the regulator body when overtorqued. The new retainers threaded tips are both shorter and the tip more rounded than the old retainers.

I just checked a [newly converted] MK10 DIN retainer against an old MK5 Yoke retainer. The length from the threaded tip to shoulder of the new universal DIN retainer is almost exactly the same as on the MK5 Yoke retainer on my vernier callers. Maybe even a little shorter. The old universal DIN retainer is longer in this area.

The old universal DIN retainer required the brass washer in a MK5. I'm just not certain that the new universal DIN retainer needs the washer in a MK5.

 

[Umuntu]

The brass ring remains in the zone where the O-ring seals, it does not arrive to the conical chamfer between the thread and the cylindrical sealing zone.

In a MK5, the inlet sealing O-ring sits at the chamfer shoulder of the retainer and not at the tip. All the later SP regulators seal at the tip. In the MK 5 body the HP tunnel to the HP chamber goes right to the threads so an o-ring couldn't seal there.

 

[Angelo Farina]

In a MK5, the inlet sealing O-ring sits at the chamfer shoulder of the retainer and not at the tip. All the later SP regulators seal at the tip. In the MK 5 body the HP tunnel to the HP chamber goes right to the threads so an o-ring couldn't seal there.

Exactly.
So the washer(s) are required for keeping the O-ring to work against its proper smooth surface in the reg's body.
Without washers, the O-ring goes in too much and finish over the first couple of threads.
The original yoke nut is longer, and goes pressing against the bottom of the hole while the O-ring is yet away form the first threads:

 

[Angelo Farina]

Yesterday I received a first batch of brass washers, so I completed mounting the SP Universal DIN adaptor on one of my old MK5.
Here you see the washer:

As you see this washer is slightly too small, the external diameter should be around 14.5 - 14.7 mm, and the optimal thickness would be 2.0mm.
Despite this, I attempted to mount and see what happens. Here the washer inside the reg's body:

Here the SP Universal Adapter, with the O-ring removed from the groove where it was locking the knob, and placed at the end of the threads (as in the original yoke nut):

And here the result, after screwing the adaptor inside the body (at 30 Nm torque), which leaves a very minimum free space for the knob to rotate, but it is free-rotating without friction and should work on the valve without problems:

 

[Couv]

And here the result, after screwing the adaptor inside the body (at 30 Nm torque), which leaves a very minimum free space for the knob to rotate, but it is free-rotating without friction and should work on the valve without problems:

Thanks for the update @Angelo Farina
I take that no modification to the saddle was needed/done?