Complete 1st stage failure (scubapro MK5)

[Luis H]

Does the new stainless steel swivel retainer (PN 10-500-104) fit a MK-5 or is there a replacement stainless steel retainer specifically made to replace the original (PN 10-105-102, or PN 105-7 as labeled in my older 1976 parts list)?

Thanks

The MK-5 swivel retainer (PN 10-105-102) turns out to have a 5/16-24 threads were the one for the current regulators (PN 10-500-104) is larger. I didn’t measure it but it looks like it is about a 3/8” threads.

Scubapro is totally out of the MK-5 stainless steel swivel retainers. I was wondering if anyone knows were some may be available (NOS, reproduction, etc.). Does any of the clone regulators use the exactly the same part in SS?

I am looking for 4 to 6 swivel retainers in SS for myself, but I know of some others that are also interested in some.

If I have no luck locating some I may have some made. I am already trying to get a quote on how much to reproduce some exact replicas in SS. Below is a drawing I made to send to a machine shop.

If exact reproduction in SS were available how many of you would be interested on buying one?

Oh by the way, even in stainless steel I tend to feel like the recommended torque for this part is a bit high. I calculated the torsion, tensile and combined principal stresses caused by the recommended torque and IMHO I would fill more comfortable down in the 20 in*lbs.

 

[DA Aquamaster]

That is an unhappy development.

I have noticed that Scubapro will from time to time make a run of hard parts for older regulators if the demand is there, so with a little luck (and a lot of demand) the retainer may be available again.

I advised the previous shop owner whenever possibel to stock up on the available Mk 5 and Mk 10 parts since we serviced so many of those regulators. It is probable that many shops followed a similar policy and have the parts available, the problem would be finding them and getting them to part with the parts.

TUSA marketed a copy of the Mk 5 with the TUSA part numbers cross referenced with Scubapro part numbers. It's possible that a TUSA dealer may have a ss retainer. There were also several other companies both large and small that sold rebranded verions of the Mk 5 and they may be suitable donors for parts as well.

 

[redacted]

What do you think the chances are of the Mk20/25 ambient chamber fitting on the Mk5 body? Both use the same piston O-ring so ID should be good at the piston head. And a simple eyeball of the exterior doesn't tell me it won't work. I may have to give it a try when I have time.

I'm pretty sure at least 2 of mine are SS but I'll have to check the 3rd one.

 

[Luis H]

What do you think the chances are of the Mk20/25 ambient chamber fitting on the Mk5 body? Both use the same piston O-ring so ID should be good at the piston head. And a simple eyeball of the exterior doesn't tell me it won't work. I may have to give it a try when I have time.

I'm pretty sure at least 2 of mine are SS but I'll have to check the 3rd one.

The piston/ O-ring diameter and even the thread size may be the same, since those are standard dimensions; unless they are using metric threads for the ambient chamber on their newer regulators. The cylinder depth, were the piston head rides could be the same, but that would most likely be a coincidence. The piston travel/stroke would be very similar, but I can’t think of any reason for length of the piston to be intentionally the same, since they are not meant to be interchangeable.

Interesting idea, but replacing the entire head assembly is not really what I am looking for. I have four operational MK-5’s and a number of beater (parts donor) first stages, but I don’t believe any of them has the SS swivel retainer. I only bought two new in the early 70’s, most of them are eBay purchases and I haven’t checked them all.

Thanks for idea tough.

 

[Luis H]

That is an unhappy development.

I have noticed that Scubapro will from time to time make a run of hard parts for older regulators if the demand is there, so with a little luck (and a lot of demand) the retainer may be available again.

I advised the previous shop owner whenever possibel to stock up on the available Mk 5 and Mk 10 parts since we serviced so many of those regulators. It is probable that many shops followed a similar policy and have the parts available, the problem would be finding them and getting them to part with the parts.

TUSA marketed a copy of the Mk 5 with the TUSA part numbers cross referenced with Scubapro part numbers. It's possible that a TUSA dealer may have a ss retainer. There were also several other companies both large and small that sold rebranded verions of the Mk 5 and they may be suitable donors for parts as well.

Hi DA
Do you know the model number of the TUSA clone to the MK-5?
Are they still producing it, or do you know when was production stopped?

Thanks for the info.

 

[DA Aquamaster]

The TUSA version of the MK 5 was the TR-400 Imprex.

It has not been produced for a few years - since perhaps 2002?

I suspect parts would still be available but I am not sure and I am currnently not attached to a shop so I have no easy way to check.

 

[Luis H]

The TUSA version of the MK 5 was the TR-400 Imprex.

It has not been produced for a few years - since perhaps 2002?

I suspect parts would still be available but I am not sure and I am currnently not attached to a shop so I have no easy way to check.

Thanks DA

That should be helpful.
Someone should have parts for a regulator that is only 5 years old.

 

[Leicamshooter]

Just wanted to let you guys know that my local dive shop sent it to Scubapro to see what they make of the situation. I should be hearing back soon what Scubaro says or does in regards to repairing my MK5. I will post the response as soon as I hear something. It doesn't sound to good from the replies that have been posted.

Thanks,
G Medina

 

[Luis H]

Just wanted to let you guys know that my local dive shop sent it to Scubapro to see what they make of the situation. I should be hearing back soon what Scubaro says or does in regards to repairing my MK5. I will post the response as soon as I hear something. It doesn't sound to good from the replies that have been posted.

Thanks,
G Medina

My LDS called Scubapro to ask for these parts for me wile I was there. Scubapro approach is to replace the MK-5 with a MK-25 if you can prove that you are the original owner. I don’t think it was necessary to have service records for the last 35 years.

I don’t know if this was a credit towards a new one or no cost to the owner type of replacement.

I wasn’t really interested in the deal since I like the MK-5 plus that would only cover two of my regulators. That is assuming they would accept a letter from the dive shop I used to work at in the early 70’s (I don’t have my original owner card anymore or any 35 year old receipts). The dive shop is still in business, but they are not a Scubapro dealer anymore.


In your case since you had a catastrophic failure, I would think they would be very accommodating to you.

 

[Mr Carcharodon]

Oh by the way, even in stainless steel I tend to feel like the recommended torque for this part is a bit high. I calculated the torsion, tensile and combined principal stresses caused by the recommended torque and IMHO I would fill more comfortable down in the 20 in*lbs.

I think even 20 in-lbs is marginal. I ran a quick FEA assuming 35 in-lbs, as suggested by the poster above and was getting stresses 2x the yeild value for stainless steel. I tried pushing the root radius up to .020R which helps but the limiting factor is shank below the threads. And that is where these things do seem to fail in the field. A specialty high strength stainless (say nitronic 50?) might be a better choice. Kind of a marginal design.