Gunsmithing HELP! Rotary union to barrel coupling for high-pressure flushing system.

[silpig]

Hello.

This is my first real post on here.

I've nearly finished putting together a high-pressure flushing system for chambering on my lathe. One thing I'm yet to work out is how I'm going to couple the tube from the end of my rotary union to the end of a barrel. I considered the GreTan coupling, but after watching his dvd, and asking him, I don't think it will hold enough pressure to properly pump neat cutting oil. The gear pump I'm using can output 38 bar, and the rest of the setup is rated way beyond that. From what I've read, I don't think I'll need anywhere near 38 bar, but as I said, I do want do want be able to get a good flow with neat oil. I've heard of people tapping the end of the barrel for nipples or hydraulic fittings, and while I'm sure that would be more than adequate for the pressures involved, it doesn't seem too quick or convenient.

If anyone could share there ideas, methods or experiences of coupling to the end of barrels, I'd be really grateful! Any pics would be even better!

Cheers guys.

P.S. Nice forum!

 

[Robert Gradous]

Greggs system works well with oil.

 

[colchester]

I picked up a rotary union from fleabay Check out duff norton or deublin rotary union find one in the appropriate size for your application

 

[Killswitch Engage]

Go to a tool store and get a swivel for air impact wrench. They are generally 1/4" pipe thread and can take 200psi and thee should be no need for near that much if you have the volume. You can put quick disconnect fittings onto it as well.

 

[silpig]

I picked up a rotary union from fleabay Check out duff norton or deublin rotary union find one in the appropriate size for your application

I already have a Deublin rotary union. My problem is how to conveniently and safely attach the pipe from the rotary union to the end of the barrel.

 

[silpig]

Go to a tool store and get a swivel for air impact wrench. They are generally 1/4" pipe thread and can take 200psi and thee should be no need for near that much if you have the volume. You can put quick disconnect fittings onto it as well.

Would this also do the job of the rotary union? The pump should be capable of 10 litres/minute.

 

[LRI]

K, I'll share with you a simple way to make this work. It's not the cheapest, but it's what I've used for 5x years without a single failure.

1. Go to a place like Shars.com and buy a set of 5C collets in 1/64'ths increments. Just get the cheap ones as what your doing isn't worth the extra 700 for the good chit.
2. Make a collar that will accept a 5c collet. You can find prints all over the webs for std 5C dimensions Another option is to just pick up a 6 sided collet block. Again, no need to spend oodles on it. A Shars/Enco brand will get this job done.
3. Take/make a "bottle cap" style collet nut and poke a hole in the center of it. Pick a size.
4. Make a dead center out of something tough like O-1 or other heat treatable tool steel. Thread one end of it to the same pitch as your hydraulic union
5. Fit the center through your "bottle cap" so that the pointy side is towards the inside of the collet (getting the picture?)
6. Now get some hydraulic hoses and quick detach couplers like what's used on a tractor/implements


Here's how this works:

You set up your stuff in the conventional manner. However you decide to set uo your barrel is up to you. Just leave a portion sticking out unsupported. Find a collet that slips over the OD muzzle end contour and allows about 1/2 of barrel to extend past the backside of it. Mount your "bottle cap" nut on the collet and begin to snug it up inside the collet block or collar. You want to push the center (needs to have a hole in it, missed that part earlier) against the muzzle end of the barrel. Continue snugging up until you can't by hand. Now get a wrench (2) and with one wrench on your collet collar and one on the bottle cap nut, snug it down. The barrel is captivated by the collet and the center is firmly jammed right up its crapper. The seal is surprisingly good if you do it right. The advantage with collets is you can adapt this to virtually any conventional barrel size. Only the most absurd barrel contours will give you fits. When that happens, just turn a portion (that 1st inch) down to where you can get the collet to slip over it. It'll piss and leak on you through the collet, but it'll work. If your doing a big mess of heavy barrels, just buy a "oh shit" collet made of either soft steel or brass and make it work.

Now attach your hydraulic line to the QD coupler attached to the rotary union.

Get to work! Time is money.

It's a quick/reliable/adaptable setup that's allowed us to chamber a big ol sweaty pile of man sticks successfully/efficiently for 5x years now with not a single failure. No lines popping off and no BP Gulf spills on the shop floor.

It's a bit of added work to get it done and it will cost you more sheckels initially, but the payoff is worth it in my opinion. No more turning/threading muzzles just to get a fitting hooked up and no fear of pissing that nasty oil all over the place. I've used this system to in excess of 1k psi.

Run a filter before you pump "erl" through your rotary union. Many use carbide seals and they no likey the gritty stuff.

Good luck and hope this helps someone out.


C.

 

[ugsly]

Lotsa ducktape, works great.

Case

 

[colchester]

I already have a Deublin rotary union. My problem is how to conveniently and safely attach the pipe from the rotary union to the end of the barrel.

Sorry should have read OP more carefully. As long as the muzzle end is unfinished you can tap in a thread pitch that will interface with your rotary union, you have to cut and crown when your done chambering anyway.

 

[jonaddis84]

I guess it doesnt apply to this thread, but wanted to note that my Gretan fitting took a dump today. Just started spewing oil out from inside the cup, tore it apart and cant for the life of me figure out where the leak is. This was under 100psi when it happened, but it happened on a 6mm where its pretty tough to get oil past the pilot.

I took the fitting apart and just used the swivel part, stepped it down to 1/8npt and threaded the muzzle. I just drilled and tapped it by hand while in the machine, wasnt perfectly centered, but it didnt seem to matter even at 540rpm that it was slightly wobbling. I wouldnt want to run it over 1k without making sure it was dead nuts straight, but were not chambering near that fast with HSS reamers anyway.

On another note, an example of the little things that make life easy. Always annoyed me that the oil pours out of the chamber right onto the removable gap area of the lathe then just sits there making a mess, plus drains down the side of the gearbox. Spent about 10 minutes making this thing, sure wish I would have done it a long time ago...

 

[Victor N TN]

If the barrel is already turned and / or maybe a used barrel, I have done it with a big piece of latex and double clamped it. Turn the pressure down on the relief valve. It wasn't pretty and DID leak. But it does the job.

 

[silpig]

Thanks for all the replies, guys!

I think what I'm going to do for the short term is tap the end of the barrels and attach the hose directly to the barrel via a male/male hydraulic fitting. Once I've got everything working and I get a bit more time I'll look at making up something that's a bit quicker and easier to attach.

Interestingly, LongRifles, Inc., I had thought of making something up very similar to what you described. I was thinking of using an ER40 tool holder with reduced straight shank. They have a thread running all the way up the shank (usually used as an adjustable tool stop) and I was considering using this thread to wind my "centre" in to the end of the barrel. I think the ER collets are probably a bit more tolerant of clamping upon a taper than 5c, but that may not be the case.

Thanks again!