MK 25 DIN Oring Question

[Random Dude]

Hi guys, just wanna ask for the o ring on the inside portion of the din retainer knob, where should the oring go on?
There are 2 slots there (as in the pic, which I screenshot drom the board since I wasn't able to find a clear picture showing the slots), not sure which one should be the correct one.
And would be nice if someone could explain why there are 2 slots on the din retainer knob

Thanks in advance!

 

[stepfen]

That's how the thing came out of a Mk11 regulator I am servicing these days. I'm pretty sure yours should be the same i.e. on the slot further out towards the tank.
If you put the knob in its place you will see that the o-ring is needed to keep it there.
Maybe you want to get a confirmation from people with more experience as this is the first time I disassembled a regulator
Regards

 

[DavidFL]

Here's a photo I just took of the DIN fitting with O-rings in both grooves; from the Scubapro Mk25 DIN conversion kit I bought awhile ago but haven't used yet:

Scubapro Mk25 DIN knob with O-rings

• DavidFL
• Oct 23, 2018
• 1

 

[shurite7]

The o-ring holds the knob in place - see the first picture. The o-ring (01.050.138) that actually seals to knob retainer goes onto the end of the knob retainer. The lip, which starts the first groove, stops the retaining knob from screwing into the body from over torquing.

 

[Random Dude]

Hi all,

Thanks a lot for the reply and pictures!

@shurite7 so is it the case that there should be 2 orings, of which one does the sealing job, while the other only serves as a guide for the Din wheel to not get over torqued?

@DavidFL weird to see that, cause both from the original diassembly of 2 MK25s, and 2 service kits, there were just one o ring for the din retainer knob. Perhaps I should just reuse the old ones, seeing as how only one of them is needed to generate a seal.

@stepfen Thanks a lot for the pic, illustrates a lot as to where the oring should be. Probably gonna need to reopen the regs since I seem to have put the o ring on the other groove instead.

 

[guruboy]

The sealing o-ring goes inside the end of the DIN.

The metal lip keeps it from getting overtorqued.

The o-ring on the outside just keeps the DIN wheel from sliding. It doesn’t seal.

 

[guruboy]

Red o-ring : seal
Yellow o-ring : useless on Mk25
Green o-ring : holds wheel
Blue metal rim : prevent over torque

 

[Random Dude]

@guruboy Thanks for the comprehensive reply!

If you don't mind me asking, why is the yellow o ring useless on the MK25? What function does it originally serve? I have noted that MK20s seems to have 3 grooves on the din knob retainer too, and just curious as to their actual function if on a regulator that needs them.

Is it a DIN 232 bar vs DIN 300 bar thing?

Thanks!

 

[shurite7]

@shurite7 so is it the case that there should be 2 orings, of which one does the sealing job, while the other only serves as a guide for the Din wheel to not get over torqued?.

Yes, the schematics only show two o-rings; the one on the end (red) and the other (green) which holds the wheel. There is no o-ring in the schematic for the groove (yellow) in the middle. Guruboy also explained what the lip is for.

 

[DiverJM]

So, based on this thread, Does the scubapro din conversion kit contain an extra O-Ring? I’m converting a mk17 evo to din.