Custom Scuba Tools MK 5 and MK 10 Piston Stem O-ring Tool

[Couv]

MK 5 and MK 10 Piston Stem O-ring Tool

I just received my new toys from Herman and I am impressed to say the least. Herman’s Custom Scuba Tools MK 10 and MK 5 piston stem o-ring tool makes installing the piston stem o-ring an easy task. If you've ever attempted to install the piston stem o-ring, you know it can be a chore unless you have a specially designed tool to do so.

At first glance the Custom Scuba Tools device looks very similar to the other tool available.


They also operate based on the same concept; however there are some important differences. The older design when used without mounting it to a tank or held by some other method is very awkward.

Thanks to the design of the Custom Scuba Tools lower guide, it can be used on a flat surface such as a work bench or table.


The o-ring insertion rod of the currently available device is a single diameter and will pass through the regulator body and o-ring. A close inspection of the CST insertion rod reveals a couple of improvement Herman incorporated into his ingenious design. The insertion rod is machined in a fashion so that only the end of the dowel will fit into the o-ring groove. This prevents the rod from pushing the o-ring past the groove into the high pressure chamber. The same end of the rod has a slot which guides the o-ring into place. A 360 degree twist of the rod seats the seal in the groove.



My very first attempt at installing a new o-ring was successful and took 10 seconds flat. Compare that with having to first mount the regulator body in a vice or on a tank valve and it is easy to see why this design is superior.

The Custom Scuba Tools o-ring insertion tool is competitively priced and much easier to use than the tool currently available.

Look for Custom Scuba Tools on eBay, at Shop Online or PM Herman on ScubaBoard.

Another well made tool from Herman-thanks.

Couv

One clarification, there are 2 separate tools, one for the MK-5 and another for the MK-10. Any time you try to make one tool do to many things, it does not do either as well as one specific tool and since one of the goals was to make a better mouse trap, I made a model for each reg. The one shown is for the MK-10 (white), the MK-5 is black for no other reason than to easily distinguish one from the other, both are made of delrin. The basic design is the same, just the dimensions are different to fit each reg.

 

[halocline]

Great looking tool, I'm ordering one today. Thank you both for making this happen!

 

[herman]

One clarification, there are 2 separate tools, one for the MK-5 and another for the MK-10. Any time you try to make one tool do to many things, it does not do either as well as one specific tool and since one of the goals was to make a better mouse trap, I made a model for each reg. The one shown is for the MK-10 (white), the MK-5 is black for no other reason than to easily distinguish one from the other, both are made of delrin. The basic design is the same, just the dimensions are different to fit each reg.

 

[Zung]

Herman’s new tools for servicing the Scubapro Mk5 & Mk10, take 2

Servicing the SP Mk10 has been my worst nightmare since day one. The critical HP O-ring is buried inside the body; coaxing it out is difficult at best and putting a new one back in is worthy of my best collection of curses: the bore, or channel where it lives is so short, it just keep falling out.

Then herman comes along with a great idea: he opts for single purpose toolsets, one for the Mk5, and one for the Mk10. Now some real nice features can be designed in.

The tool is made of 3 parts: the left white part goes to the HP side to hold the reg in place and to act as a guide for the sitting of the O-ring, with a nice domed part to ease the setting. The right white part acts as a guide for the insertion of the O-ring, and a brass rod is provides to push the O-ring in place.



A hole in the left part lets you screw it down, but that’s not required, the whole rig stays put even with a DIN attached (just for show and out of laziness, not a best practice).



All there is to do is to squeeze the O-ring and push it in the right part,



Place it in the IP side of the reg, and use the rod to push the O-ring down into its groove.



I must admit I am a bit apprehensive at first and readying myself for a fight as usual, but it turns out the whole operation lasts less than a minute, and the O-ring finds it way to its cozy new home even before I realize the job is done, no cursing and no bloodshed!



Thank you herman for a great tool. A must have for all of you who service Mk5 & Mk10.
PM him if you’re interested.

 

[halocline]

I finally got around to rebuilding a MK10 with Herman's tool this morning. All I can say is HOLY CRAP this thing works great. I put the o-ring in the white plastic part that goes in the ambient chamber, stood the reg body up on the HP side part, and pushed the brass rod in, expecting to have to monkey around a bit. Nope.....just a gentle push/twist and the thing is installed in a second or two.

Thank you Herman for making this great tool.

 

[herman]

Always good to hear the tools are working well.

 

[halocline]

Now if you could build one to remove the old o-ring in a guaranteed scratch-free way in 2 seconds...

The doublehook pick works well but still takes some fiddling.

 

[herman]

Tall order, not likely to be something I will do but always open to ideas......I do have early plans for similar models for the MK-7 and maybe some of the clones.

 

[redacted]

Now if you could build one to remove the old o-ring in a guaranteed scratch-free way in 2 seconds...

The doublehook pick works well but still takes some fiddling.

Tall order, not likely to be something I will do but always open to ideas......I

I think it is called a Mk20/25. However, I am quite sure that a sufficiently inept tech could manage to scratch critical sealing surfaces with them also.

 

[Zung]

... However, I am quite sure that a sufficiently inept tech could manage to scratch critical sealing surfaces with them also.

No Sir, I tried everything I could but so far have failed to ruin anyone.

That being said, I wonder if a delrin or brass rod of the same diameter as the bore, and possibly a lightly slanted edge, would be enough to push that O-ring out?