Silver brazing a threaded bar onto a tang

C

Conor09

Joined
Apr 8, 2009
Messages
9
Good day,

This question is posed to any knifemakers with experience in brazing a threaded bar to a carbon steel tang:

I have an older (Effingham) Blackjack model 1-7 with the leather disk handle. The thread at the end of the tang is in really bad shape flattened and deformed and does not allow the nut to tighten before popping off of the thread.

Here's the thing: I could send it back to Bark River Knives because their excellent warranty would allow it to be fixed but I would like the knife for an upcomming trip. I am sure that I could get a local engineering shop to silver braze a theaded bolt shaft by means of a tongue and groove joint as described by Wayne Goddard in his "$50 Knife Shop". However I have no personal experience or knowledge of this procedure.

The engineering shop would most likely have no experience brazing a knife tang. Is there anything that they should be made aware of? Is there any danger of overheating the tang and damaging the temper using this method?

Obviously the blade and guard would need to be adequately protected but I am concerned with potential problems that may arise with the actiual brazing procedure.

Thanks for reading this!
 
you might be able to go to a smaller die and rethread the end. i would not want to trust silver solder to hold. you could fix it temporarily with some jb weld or superglue until it can be sent in for a proper repair.
 
Thank you Richard, I have indeed considered that route and it may still be the correct option.

I was however thinking of Silver Brazing which is (i have read) much stronger then silver solder. It also appeals to my (hopefully not misguided) sense of making an elegant repair to a knife that I really like a lot!

Thanks again!
 
Well, bear in mind that brazing and soldering are one and the same, with the distinction being made on a rather arbitrary line with respect to the filler alloy melting point. As long as the person doing the brazing is competent, I wouldn't be worried about damaging the temper, the end of the tang is a long ways from the edge. If you're still concerned, keeping the blade immersed in cool water while you do the brazing should prevent conduction from building up enough heat to even warm the blade, much less damage the temper. A tongue-and-groove is the way I would do it as well, if it was my project.

That being said, sending it back to Bark River would guarantee that nothing goes wrong at all, and they'll get it back to you razor sharp, beautiful, and good-as-new. If you let Mike know your time constraints, he might be able to get it back to you in time anyway, he's always doing his best to help people out. Worst he can say is that they won't be able to make it in time. I'd grab the phone and find out! :)
 
Thanks for your advice Komitadjie. I may well still send it back to Mike (it has been before for some blade rejuvination.:)

I am however curious more about the possible effect of the increased heat of brazing upon the heat treat of the tang more so than upon the blade being as you said being far removed from the end of the tang..

Thanks!
 
I would try re-threading the tang before I tried any kind of welding or brazing. I think it would be an easier and cheaper fix with less worries about heating the tang.
 
Can you add metal over the end of the tang, then re thread it for the nut that you have available?
 
Properly silver brazing the tang should hold. Clamp the tang in a bench vise, and use a high temp silver solder. The vise won't let the heat past it to the blade.
You can even have it welded in the same manner-just make sure the threaded rod is straight with the tang before you affix it. Welding is stronger than brazing.
 
Thank you for all your replies and input! After having a careful look at the threaded portion, I think I'll try and clean up the existing with the correct size die if that doesn't work I'll try to recut the thread with a smaller die and if that doesn't work I'll consult a professional shop to do the brazing for me.

Thanks again everyone for taking the time to reply to me!
 
Smaller die means smaller nut. I think you could use a threaded insert in the nut after tapping it larger for an insert. Chasing threads that are already stripped will not likely help. Probably not worth it. Sounds to me like an error in manufacturing the nut or threading the tang. If you wish to repair the threads you need to decide which is damaged, male or female (probably both now). Or was the nut tapped oversize or the tang threaded undersize, also possible.

I'm no knife expert though, just a machinist with an interest in knives.
Jeff
 
Turnmaster thanks, I only got to read your reply now but some of what you said played out.

Yesterday I popped out to Builders Warehouse (our version of Home Depot) and picked up a tap and die set with some cutting fluid and got to work. Having a small suburban apartment I don't have a work area or most of the bench tools handy, so I clamped the taped blade to an upright on an old writing desk. I first attempted to clean up the threads with a 6mm die but afterwards the threads still looked dodgy so I filed all the old thread off, luckily managing to keep the tang-end more or less round. I used a 5mm die and half an hour later ended up with a very neat looking thread. It is as you said, a smaller threaded bar now at 5 mm as opposed to 6mm, but it is a very short portion of the tang (a bit under 3/8th of an inch) and the new nut fits very nicely on the new thread, so I don't think strength will be an issue at all.

The old thread strangely was not really stripped more like flattened and uneven. When I got the knife it had not been used so possibly a manufacturing error (it happens!) The original nut appeared like a standard 6mm thread nut which had been polished flush with the end of the tang, the thread was undamaged. The underside of the nut remained unpolished and still had the littled markings you see stamped on them.

On the whole even though I kn ow it's not rocket science I am quite happy with my effort considering that I have not used a tap and die set since my one and only lesson at age 13 at school!
 
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