Brazing with acetylene torch

[cyberdoc]

I am a newbie. I just made my first blade from O1 using files and handtools. I was planning to Braze a brass butt piece on the knife with a torch. Any words of wisdom on how best to do this ?
I've read some about it in Step by Step Knifemaking by David Boye but the section on the butt piece is pretty sparse.
This is my first attempt at brazing. I've always silver soldered the bolsters on the kit knives I completed in the past.
My first attempt was unsuccessful. I used lots of flux and cleaned the pieces well and at first the result looked just like the pictures in the book before grinding. But when I began to shape the brass with belt sander the brass fell right out.What did I do wrong? Any suggestions would be appreciated.

 

[Snickersnee]

I suck at brazing and soldering, but the two most common problems are not roughing up the work pieces, and overheating the work.

Disimilar metals expand and contract at different rates, and this can cause them to seperate.

 

[magnum .44]

i would just use low temperature silver solder, it's strong, and randall knives uses it for there survival knives to hold on the handle.

 

[Ruppe]

I do not quite have the picture here. What type of handle material are you using? If this is a through tang, you should tap the but cap and thread the tang. If you are talking about rear bolsters, try pinning.

------------------
Ron Ruppé
www.ruppe.com/Knives/index.htm

 

[cyberdoc]

Ruppe - it is neither a rear bolster nor a rat tail tang. I'm making a buttcap by brazing between two pieces of brass added on to the rear part of the tang. I've pinned the brass to the tang and just have to braze to fill the gap between them.Hope that makes sense.

I got the idea from Step-by-Step Knifemaking by David Boye. Rear bolsters would have been easier but I thought I'd try something different.
I haven't had a chance to get back to it yet since I've been working on another project. If I can ever get it to work I'll try and post a picture.

 

[Cougar Allen]

It's hard to say what went wrong without seeing it, but it sounds like you didn't heat it up enough. Then the braze doesn't adhere well and it could fall out like that.

Brass brazing doesn't require as thorough cleaning as silver soldering, and you've done that successfully, so I doubt it was insufficient cleaning. It doesn't require a tight fit either, but it does have to get much hotter than silver soldering. The joint has to be hot -- if you put the flame on the brazing rod and drip it onto a relatively cold joint it won't stick -- the joint has to be hot enough to melt the rod.

-Cougar Allen :{)

 

[cyberdoc]

Thanks Cougar. That sounds like what must have happened. I didn't get it hot enough. I was a little nervous about melting the other brass pieces so I probably skimped a little in the heat department.

I appreciate the knowledge you shared. I'll try the brazing again and let you know if I succeed this time.