Advice re: Scubapro Mk5 or Mk10 DIN conversion

[Enraptured of the Deep]

I will be grateful for advice on my plans regarding first stages. I am joining the regulator self-service club. To keep the maintenance easy, I am switching over from Scubapro Mk25s to semi-vintage Mk5 and Mk10 first stages. I have two Mk5s, one with a thin all-metal yoke and one with a thick all-metal yoke, and I am about to receive a Mk10 with a thick all-metal yoke.

I have been diving sidemount doubles for the past half-dozen years but am switching over to a backmounted single-tank DIR rig. Why? The dive op I am diving with these days does shore dives almost exclusively, often with longish walks, and I end up being the only sidemount diver. Backmounting will put me into the same setup rhythm as the rest of the crowd and especially my perma-buddy (wife).

I prefer DIN connections for all the usual reasons (not trying to start a flame-war, just expressing my preference -- I also prefer he/his). I would also like to end up with a pair of first stages that are approximately the same for sidemounting, for those times when the spirit moves me. All tanks at my usual dive op are aluminum 80 or 72 cu. ft. (12L or 10L) cylinders with convertible pro valves, filled to 200 bar (2900 psi). That means the thin yoked Mk5 won't work as is, since it is rated to only 2250 psi (155 bar).

I am planning to buy one Scubapro universal DIN conversion kit, which I understand will work with the Mk10 without any special installation arrangements. That would free up a thick yoke, which I would move over to the Mk5 that currently has a thin yoke.

These moves will result in a Mk10 DIN for backmounting and a pair of Mk5 yokes for occasional sidemounting. All three first stages would be ready for 200 bar tanks. In fact, I would plan to bring at least one of the Mk5s with me as a backup, in case the Mk10 ever has a problem. (At some point in the future, I may consider switching the Mk5s over to DINs, recognizing that this would require adding non-OEM stainless steel washers as spacers, per an old Scubaboard thread.)

Does that all make sense? Am I missing anything with this plan?

 

[lexvil]

The Mk5 is as good a regulator as you’ll find, that said I would bother with them, they are simple and rugged and plenty of them were made to salvage for parts but some parts are only available by salvage, like pistons which you may never need to replace but...

You can find current regulators with easier parts access, things like Atomic “Z”’s are found for low cost alternatives, scubapro MK 11 or 17 are very easy to find at great prices and more often than not will work fine and not need immediate service.

Your plan will work by the way.

 

[tbone1004]

The din MK10 is good for 300bar. I have them on my mk10's.

@Bryan@Vintage Double Hose has all the parts for the old first stages as well as videos on how to service them if you need them.

 

[Enraptured of the Deep]

Thanks, @tbone1004 . I have discovered VDH's excellent selection of parts. And it was the video series by @Bryan@Vintage Double Hose that made me realize that the service procedure is not rocket science. I just finished reading Regulator Savvy, too, so I'm not completely ignorant of the science.

Thanks also to @lexvil for the alternative selections, but I have already acquired the Mk5s and Mk10 and the tools to service them, which definitely makes them the low-cost option for me. I'm looking for stupid-easy.

 

[Couv]

(At some point in the future, I may consider switching the Mk5s over to DINs, recognizing that this would require adding non-OEM stainless steel washers as spacers, per an old Scubaboard thread.)

You might save yourself a bit of grief & work by just going with 2 MK10 DIN regs and keep the MK5s as yoke regs. However, if you're determined to convert the MK5s, I think rather than a stainless steel washer, it might be better to go with something softer like a brass washer as a spacer. The ss being harder than the yoke retainer and body would maintain it's shape in a fight with the brass parts.

 

[halocline]

If you keep your eyes open, eventually you will find MK5 DIN retainers, but Couv's idea is fine as well. The MK5 with the thinner yoke probably does not have an end port (which I use all the time but maybe isn't important to you) and it probably has a brass turret retainer, which you will want to change to stainless if Bryan still has some at VDH. The brass washer idea for the DIN retainer works well, you need about 2MM of thickness.

Neither the MK5 nor MK10 are ideal for HP tanks, but they do work fine. There's just a bit more extrusion of the HP o-ring and resulting rise in IP at tank pressures above 3000 PSI. I would make sure you rebuild them with 90 duro (not the OEM 85 duro) 010 o-rings in the HP piston spot if it's your intention to use either with HP tanks. I keep a pair of MK15s around specifically for that. But I have used both MK5s and MK10s, yoke and DIN, with HP tanks and had no problems.

 

[Angelo Farina]

I have just converted my MK10 to DIN using the ultra-cheap Scubapro Universal DIN adaptor kit, here you see the result. 35 euros spent very well:

I have other two of these SB universal kits, and I am looking just now on mounting them on two of my four MK5, the two newer ones (with SPEC and 5-ports swivel).
I have also purchased two Trident A166 DIN adaptor kits, hoping that they mount properly, which instead is not (they lack the groove for the O-ring close to the threaded part, and the end of the barrel is too long for screwing in properly).
However these Trident kits have a nice all-brass knob, instead of the "modern look" plastic-rubber one that Scubapro is using now, and shown here above on the MK10.
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).
I am also evaluating of using the brass knob (Trident) or the plastic one (Scubapro). Aesthetically I prefer the Trident one...

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

The Scubapro barrel screwed in without washers. The remaining space for the knob would be just 22.3 mm, and the O-ring placed in the small groove at the end of the threads would finish against the threads.

The Scubapro knob is 24.1 mm thick, so the washers should be at least 1.9mm for allowing it to rotate freely - hence the recommendation for 2mm is sensible.

The Trident A166 knob is slightly less thick than the SP, at 24.0mm - with it, a washer of just 1.8mm would be OK.

The O-ring (damaged by previous insertion without washers) placed in the small groove at the end of the threaded part - as you see, there is no O-ring in the larger groove.

The MK5 with the Scubapro knob installed, using two washers of 1.2mm each. The knob is wide free to rotate...

Here instead with the Trident all-brass knob. There is slightly more free space for rotation and the aesthetics is much nicer...

Here the two washers I employed for this test: they have an external diameter of 14.7mm and a thickness of 1.2mm, which is probably slightly too much.
But using only one, the knob gets locked against the saddle..

Conclusion and questions:
Do I keep these two washers, albeit a little too thick, or do I wait for the brass ones, which are just 1.0 mm each?
And do you suggest I use the original Scubapro plastic-rubber knob, or is better to use the trident all-brass one, which is more similar to the old one for the MK5 regs?

 

[Couv]

do you suggest I use the original Scubapro plastic-rubber knob, or is better to use the trident all-brass one, which is more similar to the old one for the MK5 regs?

Hi Angelo, I have no experience with MK5 DIN original, Trident, or a modified MK10. Not being able to touch/feel/test it puts me at a disadvantage. I would want to properly torque (266 inch lbs/30 NM) the fittings down and do a fit/feel/pressure check. @Luis H might be able to chime in from an engineering point of view. Brass seems a more reasonable material; however, I think you hit the nail on the head with this statement:

...I ordered brass washer with a thickness of 1mm, when they arrive I will decide which are better...

Aesthetically I prefer the Trident one...

Totally agree!

I'll attach a document that may be of some help, but probably not as what you have is a modification.

 

[Enraptured of the Deep]

The question I have about using a brass washer (or two) as a spacer is this: Won't it corrode in salt water? Jammed in there under torque, I wouldn't expect it to rinse well.

In following thread, Awap mentions his brass washer fix, and another user mentions a couple of stainless steel washers:
Scubapro Din Adapters - Mk5

@halocline My thin-yoke Mk5 does indeed have an 5th end port on the turret. I haven't opened it myself, so I don't know if the turret bolt was ever upgraded to steel, but I will certainly do so at the next rebuild.

 

[Angelo Farina]

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 :

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:

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.