What to back a braze joint with that won't stick?!

[dan.taylor.1]

Hi folks,

Need to braze up some holes in thick brass hinges so they can be redrilled, what can I back the hole up with that won't stick to the braze? Would a bit of aluminium plate work?

Any help much appreciated,

Cheers, Dan

 

[voipio]

Graphite block? Provided the braze doesn't contain titanium, which sticks to graphite, apparently.

 

[Tigman]

Put a bit of brass Rod in the hole braze one side , turn over and braze the other side , it will all blend in !

 

[dan.taylor.1]

Put a bit of brass Rod in the hole braze one side , turn over and braze the other side , it will all blend in !

Ideally yes. But the customer has made a right balls up of the holes, they're most definitely not round!

 

[dan.taylor.1]

Graphite block? Provided the braze doesn't contain titanium, which sticks to graphite, apparently.

I'll have to get some, don't have any and this is a rush job apparently (aren't they always!)

 

[voipio]

Carbon, as an alternative? Or do a test piece with some scrap brass with a hole in it, and some ali behind. Make sure that the brazing spelter melting point is well below that of brass, and the ali, if you decide to use that. There are some high temperature braze metals around, which might be best avoided.

 

[Brad93]

Ceramic weld backing tile or graphite

 

[dan.taylor.1]

Just had a brainwave, I've a graphite crucible, I can use the bottom of it as they're only small holes, might need some fixturing to keep everything in place but saves waiting for an order to come in.

 

[dan.taylor.1]

I think you can discount this option purely by checking the melting points.

Yeah, but I use it for backing up steel when I need to weld a hole up and haven't had any issues tbh.

 

[8ob]

Brass weld instead of braze?

Bob

 

[voipio]

The colour of the brass, and its temper, will change quite a bit, as a result of the heat from brazing.

 

[dan.taylor.1]

I don't think the colour matters as its painted anyway. Plus the jolt head will cover most of the repair.

 

[tom2207]

motor brushes if you have any laying about ,,, fiddly but if it gets you out of a hole .

 

[dan.taylor.1]

Managed to get them done. Tig brazed them in the end with a polished stainless backer, just washed the heat with the tig arc and melted the rod in one side, clean it off and do the other side.

 

[Brad93]

that ceramic weld spray works too

 

[dan.taylor.1]

that ceramic weld spray works too

Never thought of that. Could have coated the stainless in it maybe. I use it on shrouds and tips, way better than the normal tip dip!