Repair a hollow brass or bronze casting help

I've had good luck with JB Weld and have also used Bondo to repair/rebuild a broken prewar switcher headlight.

I would start with the JB Weld and try that first if it was me.

Tom 

That appears to be diecast zamac. I would go with JB Weld. You can surely sand it. Its only slightly harder than bondo type body filler.

Pete

Thanks guys, I'll grab some at the Ace Hardware. Pete, the image isn't what I'm repairing, only a visual. I'm thinking brass.

Well, flying blind (photo did not load for me), but if it is a small hole or void, the easiest thing to use is Bondo or even Squadron modeling putty (it's "bondo-ish"). Let it dry overnight, then sand or file it to shape. After all, Bondo is used on automobiles, and I have used a ton of it in bashing models.

Epoxy will do, but Bondo is much easier to work with. I generally use the epoxy where strength/handling/oils are factors, or as an adhesive.

Why did you say you could not sand the epoxy? You can sand almost anything, except maybe peanut butter. Problem is, epoxy is so tough that sanding can take forever. Epoxy wants to be filed.  

If it is brass then you can solder it. Use an active flux and put something inside to keep the solder from dripping through like a wood dowel.

Pete

You can solder that easy but its deformed so your best bet is to use the bondo or putty to fil it an re sculpt the profile.

Small part, looks a tad on the delicate side,  I'd go with model putty.  

Keep us posted!  

Mitch 

  I trust JB-W not to crack or chip out while working it more than putty.

  I prefer to use putty as you would automotive body putty; as a skim coat somewhere between Bondo and filler primer. 

Plastic wrap will leave JB-W smooth and flush with care. Peels off easiest right near end of set time vs hours. Folds and covered edges, JBW may grab the plastic and hold it fast when fully set.  Experiment a bit.

Work it with wet fingers and tools to keep it from sticking to tools and digits (mostly). The more it's set up, the easier this is. But you have only a short time to consider. (water for putty too for that matter.)  Like the wrap, a plastic straw could be used as a backer to keep the pipe unblocked for a better look if raised. I'm thinking on a string to pull it out  at "half set" easily if needed.

5 min. JB-W is my preference for sculpting as the original JBW droops some with the long set time.

Working JBW with sand paper asap helps, but beware of grabbing and paper loading up with gunk. (filing needs to be a good cure or you may foul the teeth permanently )

Removal of a botched job would be easier with putty

How smooth? Two applications here; look close at the corners, vertically for  the color lines. (and remember the camera can be crule to modelers) The whole corner was missing. The step addition cause the V...above than it blended flush on it's own with plastic wrap, and the curve made by pressing paper over the wrap for a second to smooth the rounded corner. It was backed by masking tape, pressure from forming just pushed the tape in some.

No sanding or paint was done on the upper as  I'm pretty good at color matching now (affects cure time and strength slightly)  I mist painted the step though as it turned out lighter.(different JBW tubes, and batches vary some on pigment count)