Scubapro Mk2+ M26 DIN conversion

[Mobulai]

I am glad I could help, I am just recycling knowledge from the actual gurus around here on the board

I certainly ran into a similar issue with an MK2 copy that I got exlusevly to use in Egypt a couple of years back, had it rebuilt into G5/8 at a local shop.

uses standard DIN for everything for air to 100% 02

Regarding the rebuild:

even though that is geared at Yoke>DIN conversion (whereas I am looking to convert M26 to standard DIN)

100% (pun intended)

and then I followed the Mk2 service manual up to the preliminary stage of page 4 of the manual here (Link), then I could successfully convert the reg from an M26 to a standard DIN?

also correct (by deduction, I am not that experienced at it) -- what I am certain about is we don't have to think about the seat because it's already O2 ready *phew*

I abloutely overlooked considerations about this:

Neither EPDM, nor PU are excellent in a high ppO2 environment. As you can see, you can reuse one of your FKM O-Rings, as it is the same size. The one that sits between your first stage and the cylinder valve however is a different size on your M26 barrel, compared to your DIN barrel.
I would suggest you change that O-Ring to a more suitable FKM, often called Viton, which is one of it's brand names.

definatly a major player. Tanks is always on top of the details
If I was in your fins I would end up doing it as well (I always replace my stocks with FKMs whenever accessible, even for air regs -- so my M2 copy got that treatment after getting it from the shop).

Most importantly, watchout for that torque spec -- super important.

Safe diving and fun rebuilding

 

[Mobulai]

You can limit that to France... Never seen any M26 on German, Spanish, or Italian divers kits, although it's not unknown in these countries.

germany is a bit of a mixed bag there (I am a bit confused how DIN standards translate there as actual regulation.. given it's literally Deu. Ing. Norm. ) -- haven't had that much experience with o2 in the EU (or in general tbh)

I like how you are thinking about keeping it on the M26, and worst come to worst I can reachout to that adapter. my other (not the one in Egypt on g5/8) o2 clean reg stays on M26

 

[Tanks A Lot]

...If I was in your fins I would end up doing it as well (I always replace my stocks with FKMs whenever accessible, even for air regs....

You may want to reconsider this, borrowing from another thread, specifically with regards to the O-Ring at the end of the DIN barrel.

FKMs usually do not have better mechanical properties than cheap NBR. Their abrasion resistance is on par with NBR and compression set is only slightly better. FKMs do have a much better ozone resistance than NBR, which is about the only thing of interest in your specific case. That AP1166 O-Ring is exposed to the environment extensively.

ScubaPro got it right with their choice of PU (Polyurethane) for this O-Ring. PU has one of the best abrasion resistance and short term resilience that you can currently find in an O-Ring material. It has a horrendous compression set, which is of no interest if you don't plan to keep your regulator attached and pressurized for a week or so. PU has better mechanical properties than EDPM, FKM or NBR with one of the best ozone resistances (At least on par with FKM). In fact it has one of the best abrasion and short term set resistances of all o-ring materials I know of.

PUs shortcomings are of no interest for the diving industry, which would be:

• Temperature range of only -35°C to 80°C. The material can be adjusted for slight increases in both directions. Despite this low temperature range, it is commonly used in industrial O2 settings. The low ignition point must be taken into account.
• Low resistance to ketones, acids, chlorinated hydrocarbons, brake fluids, etc.
• Terrible compression set

As FKM is comperatively expensive for normal air usage, I would stick to NBR, or in some cases PU.

Most people that ran a fleet of rental cylinders with FKM O-Rings sitting between the cylinder valve and regulator can attest to it's rather poor mechanical properties. NBR does slightly better, while PU outperforms both by a long shot.

 

[bipolarbear]

I abloutely overlooked considerations about this:

definatly a major player. Tanks is always on top of the details
If I was in your fins I would end up doing it as well (I always replace my stocks with FKMs whenever accessible, even for air regs -- so my M2 copy got that treatment after getting it from the shop).

Most importantly, watchout for that torque spec -- super important.

Safe diving and fun rebuilding

Thanks both - that was something that I had given some thought to but hadn't yet worked out a solution for. I've just sourced a Mk2 Plus Nitrox service kit from the EU (prohibitively expensive...) which should arrive in a few days. I'll be sure to do the conversion with proper O2 lube and rings - this one's my 100% reg so critical it be done right!

Now just to source the torque ratchet and 1" socket. Then I'll have everything I need.

I would usually just send this to a shop but it's been surprisingly difficult to find anyone able to do this for me locally in Hong Kong.