Very simple bore-hawg.

[Selador]

In my second build, I am working with 1/2" stuff.

When it came time to prepare the tee for the piston and barrel, I discovered that the "stop" inside the tee, (Which limits how far in, the pipe can be inserted.)...

Was not a ring.

Instead, they simply made the entire tee inside body thicker, between the two "stops".

I found myself without a drill bit big enough to hog all this out.

Also didn't have any ready-made sanding drums of the right size. (Besides, those sanding drum things fall apart if you so much as look at them crooked.)

So, I fell back on an old method of sanding inside a pipe.

Get a suitable sized dowel rod.

You can use an old bolt, if you wish. It'd last longer, and be stronger. It'd just be more difficult to cut than a dowel.

Cut a slit in the end of the dowel.

Cut a suitable sized piece of sandpaper.

Fold the sandpaper so that the grit is on both outsides.

Slide into the slit, in the end of the dowel.

Now chuck the other end of the dowel up in your drill, and hawg away !!

Using a knife, files, a rolled up piece of sandpaper, etc... The sort of hand tools I had around... It would have taken me at least an hour to hog out the inside of that fitting.

Using the 'flapper-hawg', it took me roughly three minutes to get it suitably hogged out.

Note: It is easier to work with, if you make the shaft, (dowel rod), only as long as you really need. If you make the shaft too long, it will flex.

Edited to add: If you use a long enough dowel, you can also use this to polish the inside of your barrel.

[jrrdw]

No picture of the finished piece? Would like to see how this tool did...

[ThornsofTime]

This type is heavily used in the jewelry manufacturing world. Dunno whats its officially called, but when I worked at Jostens we called them "split mandrels".

As a side note... you can use the length of sand paper strip you use to change the diameter of the tool, and hold it all together by rolling on an o-ring or rubber band. This keeps those "flaps" from ripping apart and turns it into basically a drum sander.

Riogrande.com sales lots of different models that are professional grade if you dont wanna make your own. Link to some here if your interested.

http://www.riogrande.com/MemberArea/Pro ... hing+Equip

[Selador]

No picture of the finished piece? Would like to see how this tool did...

I already glued up the tee. So the comparison picture will be a bit difficult.

Here it is.

Note that the finished tee is already glued inside a 3/4" female fitting.

So, I put a green dot on roughly the same spot on the lip of the two tees.

Now look down toward the hole in the left side, on both tees.

The ridge that you see above the hole on the intact tee, is the same thickness as the 'stop ridge' on all 1/2" fittings. Only, the entire 'pipe' is that size from that point, to where it becomes the 'stop ridge' on the other side of the tee.

In the finished fitting, the entire region of the tee has been hogged out. A 1/2" pipe will slide completely through the tee.

I hope this helps.

This type is heavily used in the jewelry manufacturing world. Dunno whats its officially called, but when I worked at Jostens we called them "split mandrels".

I wasn't aware that someone had started manufacturing these. Thank you for the link.



Don't think I'd buy one, though, when it is so easy to make my own.

I first made and used one of these, back in cub scouts. That's 40 some years ago.

[Technician1002]

Using stick on sand paper with a lump of paper towel under it works well too.

[Selador]

Using stick on sand paper with a lump of paper towel under it works well too.

DOOD !!

I have been wondering why you went to all that work on that skanky old piece of pipe.

You could have just bought a new one.

And that one is so rusted and pitted, I would have to wonder about it's integrity under pressure...

[Technician1002]

I went to work on that piece of pipe because it lacked a huge seam. I checked the integrity by cutting into it and checking the maximum depth of the pits. The pits are surface defects but do not impact the integrity of the pipe. It is used at a relatively low pressure and needed to be round and smooth on the inside. It did not take long to get a polish on the inside. In cutting threads, none of the pits were deep enough to show in the cut threads. It will be fine at it's design pressure. The pipe is not cheap thinwall stuff.

You can see the remains of the seam in the reflection of the golf ball. Many other pipes I looked at have a deep valley in the seam or a tall ridge. This rusty pipe was easier to polish flat for a valve.



The cut end shows the depth of the pits in relation to the thickness of the pipe. The pipe should have no problem holding 200 PSI on the outside. The good metal is over twice the thickness of the propane tank it is welded inside.



The Propane tank is much thinner.

[ThornsofTime]

No problem mate. Yeah I Have basically the ones in the link, but hadn't thought of using a longer one to polish my barrel.... I see a 3ft dowel in my future... or maybe a steel pole to reduce flex... thanks for the idea

[Technician1002]

This is not a barrel. It is a valve. Full flow 2.5 inch. I use a 3 inch ABS barrel on my other launcher. It is already smooth and quite slippery for launcing garden produce.

This hobby is addicting. I started with a 1 inch piston. I have 2 2inch porting piston launchers and am now working on 2.5 inch.

[Selador]

I went to work on that piece of pipe because it lacked a huge seam. *snip*

I kind of expected the same answer that I would have given you...
"Because it's just so damn cool !"

No problem mate. Yeah I Have basically the ones in the link, but hadn't thought of using a longer one to polish my barrel.... I see a 3ft dowel in my future... or maybe a steel pole to reduce flex... thanks for the idea

It also occurs to me that you could pack foam rubber inside those 'curves' you see on the sandpaper. To kind of pack it out and make sanding/polishing/hogging out, a larger bore, a bit easier.

This hobby is addicting. I started with a 1 inch piston. I have 2 2inch porting piston launchers and am now working on 2.5 inch.

Tell me about it !

I spent most of this month's grocery budget on parts to build spudguns.

Parts to dink around with this and that, and try different ideas.

If that isn't the definition of addiction, I don't know what is. LOL

I started with a 1-1/4" valve. Now I am working on a 1/2" valve.

Been searching for a while now, for guidelines for troubleshooting a piston valve.

Not basic instructions for building one. I can do that. I mean troubleshooting a built valve that isn't quite working right.

Edit: I didn't know D I N K was a smiley.

[Technician1002]

For troubleshooting a piston valve, some of the issues with them are in the Wiki.. Leakage, friction, and ratio all come into play to get one working properly.
http://www.spudfiles.com/spud_wiki/inde ... ston_valve

Knowing the parameters of how they work help in diagnosing them when they don't work.

The pressure in the pilot has to drop low enough to unbalance the piston. This pressure varies depending on the ratio. Friction and excess leakage into the pilot are common problems keeping the piston from moving.

[Selador]

The pressure in the pilot has to drop low enough to unbalance the piston. This pressure varies depending on the ratio. Friction and excess leakage into the pilot are common problems keeping the piston from moving.

Pilot pressure drop is exactly what the problem was.

I'll post a new thread with the details. I was asked to post pics and a decription of the problem.

The power has been out, where I live, for a couple days, so I have a lot to catch up on. I'll get to the thread when I can...