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DIY Tool for removing rear inlet valve

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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popgun pete

Well-Known Member
Jul 30, 2008
A simple tube spanner can be made to remove the rear inlet valve body. Recently I decided to make one out of some aluminum tubing of 19 mm OD and 16 mm ID. I had thought that this would be too thin and weak in cross-section for the job, but as I had a length of it from a gun project that never eventuated I decided to make one and see what happened. The two notches in the rear of the Mares inlet valve body are 10.5 mm wide and 3 mm deep, so I cut lugs using a hacksaw onto the end of the aluminium tube that had previously been cut off square to the longitudinal axis of the tube. Aluminium is easy to work, so I removed enough with the hacksaw cutting first downwards and then radially to create the two diametrically opposing lugs which are 3.2 mm high and 10 mm wide, doing the final cutting to size with a metal file. Note that the length of tubing was first held vertically and then horizontally in a bench vice for this work. You can always take more material off with a file, you cannot put it back on, although you can cut deeper into the tube if you need to start again. I made the tube spanner 12 cm long (the tube spanner length is not critical) and drilled a transverse hole through the rear end for a T-bar (using a drill press, but I could have done it in the bench vice after centre punching the tube to stop the drill bit drifting off where I wanted the holes to go). I use an old engine push rod, but you can use a spear shaft if you have a short one that will serve as a T-handle.

It took me 10 minutes to make it and some of that time was spent clearing the work bench, finding a suitable file and two blocks of wood to avoid squeezing the aluminum tube in the bench vice. The key to using the tool is to engage the lugs fully in the slots and give a strong twist with the gun grip held firmly between your knees, there will be an initial resistance and then it will turn, getting easier as it revolves out of the rear of the grip. Sometimes the screw threads will have some sealant on them, but usually they do not as the pressure seal takes place where the well in the rear of the plastic handle molding presses against the large radial step in the metal inlet valve body. I sometimes think this stuff is to discourage DIY efforts, but if so then it is not strong enough. Never use epoxy on your gun or you will ruin it for future dismantling.

This item is so easy to make it could almost be a throw-away tool. I have undone two never dismantled before guns with it and the tool seems undamaged so far despite the 1.5 mm thickness of the lugs. A piece of aluminum tubing with a smaller ID may be better, but as this works I don't think the lugs need to be any stronger unless you were working on a speargun production line.
Here is a photo of the home-made tube spanner. It will fit the Mares inlet valve bodies, but not those on Cressi-Sub guns as the latter have a larger diameter hand pump connection thread and thus inlet valve body which is closer to the rear end of the gun. This means that a tool does not have so far to insert in order to engage the notches or slots in the rear of the Cressi guns.


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    Tube spanner for Mares 1.JPG
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good job Pete once again I have been racking my brains for a suitable tools for the various guns which I won to find a simple solution..cheers mate..
Hi Pete,
Quick question:
The OD of the tube would that work for a Seac gun as well? Would you know?
I want to make one of these, or at least buy a piece of suitable pipe, before I reunite with my gun which is store in Thailand.

I don't know for sure, but I expect them to be the same. The tube size should be OK, but the slots in the inlet valve body may be slightly different in their width. I progressively filed the metal away to achieve a close fit, so I made the lugs slightly oversize initially so that I had some material to work with. The fit is not super critical, but you want the width of engagement of the lugs in the slots to be as wide as possible using a weak (in this context) material like aluminium.
Got it, just wanted to have an idea if the OD would be OK. But 19mm is prolly OK and I'll look for a small piece of pipe, perhaps with a bit thicker wall.
Or, if anyone has a Seac gun handy and wouldn't mind taking one measurement then the one, I am looking for is the outside diameter of the valve body at the end of the gun - the one you screw the pump into.

You'll see what I mean in the schematic below.



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Pete, thats a good, easy, simple design.

I made one out of 19mm copper "water pipe" tubing as i had some lying around. It works great for the tightening and loosening of the value. I didnt make the lugs a super close fit and it moves around a bit when undoing or opposite so i use a bit of alluminium bar for that.
I think if you could use 19 or 20mm x 3mm thick tube that would be perfect.
Great Gazz,
Incidentally, yesterday I spent some time on the Italian Pescasub forum (quite an amazing place) and there was one guy there who, in an old post, said it was 20mm OD.
One of the good things about living in China is Taobao which is a mix of Amazon and Ebay. You can get everything there pretty much. From Ferraris to O-rings. So, now that I have the measurements confirmed (I'll stick w. 19mm to be on the safe side) it's just a few clicks away from being delivered to my doorstep.

This little project ended up on the back-burner for a while, but I am back on it.
Thanks to Pete for the inspiration!

As Gazz suggested I used an alu tube in 20X14mm dimensions as the 20mm OD and the 3mm walls fit the valve perfectly.

But I added a function to mine. I inserted a 14x10mm tube into the bigger tube to serve as an extension and as a sort of "foot rest" for when assembling the gun and to get the buttom of the handle off the ground. Reason is, I will have a carbon fiber grip on my gun soon and sometimes, I end up putting a lot of weight on gun as I push the nose cone into the outer tank.
Also, since I want the extension to screw into the valve itself, it has to be a smaller outer diameter - hence two two different sizes of tubing.

I think the pics will make more sense.

Here is my old and very simple tool at the top and part of the new one at the bottom:

For now, the two tubes are just held in place by a very, very tight press-fit, but I will pin it later.

I threaded the end of the thinner tube in M14x1mm so that I can screw it into the valve itself - this is for when I want to use the tool as a "foot rest" and not an extraction or insertion tool:

This is how it would look when about to insert or extract a valve:

And here it is, turned around and screwed into the valve to serve as a "foot rest":

My new carbon fiber grip wont protrude backwards as much as the original Mirage grip so there will be a bit more clearance off the ground when I do assembly which needs the gun to be mounted on its "butt":

What's left is pinning the two tubes so they don't turn within each other and drilling a hole for a rod or screwdriver to help turn the tool.

Hmmm, I just realized the times when I put the gun on its handle, I might just turn it around, nose cone down and push from the handle-side... Well, now I guess I have both options.

PS. The Mares and Seac valves share dimensions so this will work with Seac valves, too.
Does anyone know if Salvimar share those same dimensions?
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An update:
The Pump Valve Tool above has served me very well. I didn't even have to pin the two sizes of alu tube as the friction fit happened to be extremely tight.
I did a very simple modification to it a few days ago. I cut off the the male thread as I never had any need for using the tool as a "foot rest" during assembly.
I also tried my hand at knurling the tool on my my Mini Lathe but that didn't turn out too well, but that's OK.
Now, it looks like this:


The knurling makes it easier to unscrew the valve once it has been loosened up. As for the latter, I think it makes sense to make the tool long enough that you can swing a screwdriver (or whatever you use for leverage) 360 degrees freely without bumping into the rear end of the handle.
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I thought I might as well add another one I made for a local spearo a little while back - nothing too fancy. For a Salvimar Predathor this time:


And as I mentioned, I think it makes sense to make these long enough that you can turn the screwdriver a full 360 without it interfering with the handle - otherwise, it's just a lot of annoying stopping and going:
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Yeah, I have come across those service kits a few times online (once or twice on eBay) and they are incredibly costly. I guess they are targeted at resellers who need to be able to service the guns?
Yeah, I have come across those service kits a few times online (once or twice on eBay) and they are incredibly costly. I guess they are targeted at resellers who need to be able to service the guns?
A dive shop could justify that amount as it is relatively cheap for tools that will last a long time and see plenty of use if the shop services pneumatic guns, but for an individual it is a large amount, particularly with say another US$80 or so for shipping. Volume lowers costs, so selling more of them the sets could be much cheaper, but we are still stuck in the era of not servicing your own gun and leaving it to a shop who often don't want to do it, yet have that benefit of the gun warranty that keeps gun repairs their exclusive preserve.
I just ordered some spearfishing spares from the USA; order value US$82, shipping US$84, so the estimate of US$80 above was about right. Not ordering one of those repair kits, although I was tempted for a moment.
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