best way to rough up the inside of 3/8" copper tube?

A small (1/4" dia) sanding drum chucked into a Dremel.

Use a fine grit sleeve and slowest speed.

Run a 3/8 drill thru it?

rolling a rough round file in the tube. with the tube laying on the table?

Nick

You didn't say what kind of "glue" you were using. I'd suggest trying epoxy, even the "5 minute" kind should work for your application.

I suspect maybe the inside of that tubing has a film of oil on it. Try swabbing it out by pushing or pulling a small piece of cloth wet with acetone through it. Cleanliness is next to Godliness in the epoxying business.

If you really want to scarify the inside of the tubing, here's a simple way to make a tool for that.

Get a piece of rod about 3/16" diameter and long enough to go a bit more than halfway through the length of those pieces tubing.

Saw a diametrical slit across one of the ends of the rod, continuing about 3/4" down the rod.

Cut a strip of abrasive paper 3/4" wide and a couple of inches long, slide it's center into the slot in the rod and twist the rod clockwise looking at it from the unslotted end while smoothing down the abrasive paper so both ends of the paper wrap around the rod, abrasive side out. (Flip the paper over if it comes out backwards on the first try. Duh.)

Stick the rod in a drill press or drill motor and have at the inside of the copper tubing with it, working from both ends as needed.

HTH,

Jeff

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You can buy wire brushes for preparing tubing for soldering that size. Greg

I am not an adhesives expert, but played one at work. We did not have any copper things to bond, but I do know that most adhesives don't do well with copper. The copper kill the curing agent or something like that. You might do some searching on Google for the reasons, or just go to your local hardware store and buy some epoxy that is formulated for copper. You can find it in the plumbing area.

Getting a rough clean surface is probably not going to work with regular epoxy. Of course having a clean surface is going to be needed, unless maybe you use an industrial polyurethane adhesive.

Dan

Jeff Wisnia wrote:

Okay, I did try googling and did not find out much. If I recall correctly, some epoxys do not work well with copper. I would clean and rough up some copper and see how well your adhesive works with it. I think that some curing agents corrode copper and therefore you don't get a good bond even though you started with a clean surface. Dan

Simple. Using coarse media, sand blast it. It may not look like you've done much, but it will rough it up enough to create good tooth, providing you don't heat the installed pieces enough in use to cause them to expand to the point where you break the bond. I assume you're applying the tubing in one piece, by sliding it over the exposed portion, not two halves. A spring hose clamp might be a better choice in that case.

Harold

Get a chunk of all-thread just slender enough to fit inside the copper tube, but way too long. Chuck it in a fast drill, slip it into the tube, and let 'er rip! The all thread will start to wobble around, and do all kinds of terrible things to the inside surface. Kind of like what a socket does to a stud when you take off a nut too quickly with an overpowered impact, but backwards. You could probably enhance it a bit by beating the s*it out of the all-thread before starting. Wear gloves and glasses. A flak jacket can't hurt either. (:

You forgot to tell him to stick the whole works in a bucket of sand before you start the drill....

I was gonna suggest a battery terminal brush, if he had one already.

You didn't mention the size of the tubing, but a battery terminal cleaning brush works fine on 1/2"-1" sizes. For smaller sizes saw slit

They're too large in diameter, Carl, but some of the bayonet socket cleaning brushes (for lamp sockets) might be small enough.

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Grant, How bout a bore cleaning brush on a cleaning rod for a .38? Ken.

This is kinda thinking outside the box, but have you thought of other ways of attaching the copper tubing to the shanks. I don't know what kind of a fit you have-interference, press, loose fit, etc. but if the fit is good you might be able to silver solder it, just like regular plumbing pipes. They also make epoxy specifically designed for copper. To rough up the inside of tubing, mostly PEX for various gadgets, I use a wire brush attachment in my dremel, or the sanding wheel, or a fine riffler (pattern maker's rasps).

Lot of great ideas have been posted. You bring up the issue of fit. Well, I couldn't find 3/8" hard copper tubing (the straight stuff) at any local easy places like Home Depot or McLendon (a real good local hardware store) so I just bought some soft 3/8" copper tubing. The problem with soft roll copper 3/8" tubing is it's actually a lot bigger than 3/8" inside, at least .385". So what I thought would be a slip fit wound up being a rattle fit. I wish I knew where to buy 3/8" copper pipe -- that's 3/8" ID, 1/2" OD. I'm sure Alaska Copper has it downtown, but I'd probably have to buy a 20' section and I only need 1' so I'd be paying 20X the price which is something I ain't gonna do.

I used JB Weld. I made up 4 pieces, and on 2 of them, the copper was so far off center that I had to try to turn it so it would clear, and when I was turning it in the lathe, it broke loose. Pilot error probably, the other two pieces seem strongly bonded so maybe it isn't really true that this is a copper bonding problem.

Thanks, everyone.

GWE

You might want to try Loctite. If the fit is loose the bearing retainer type might work better.

If the fit it too loose and you epoxy to fill then you do have to roughen the inside. I have some old water damaged 24 and 36 grit sanding belts and disks that I use for this sort of thing. They're pretty stiff but you can roll them up in sort of a spiral tube and pull them through the tubing a couple of times.

Good luck,

Kelley

And use the stainless bristle types, not the much much softer bronze ones.

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the s*it out of you for torturing the cat." Gunner