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Brazing silver steel: any caveats/recommendations?

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Calum Galleitch04/03/2021 10:32:21
24 forum posts

I'm doing some long hole boring with unusual diameters. I can get short lengths of silver steel, but not long enough, so I'm wondering about brazing them onto a suitable shaft. Has anyone had any experiences of this? The shaft would have to be "pretty straight" but not "machinist straight", as the bit will centre and direct itself.

br04/03/2021 10:38:02
465 forum posts
4 photos


Edited By br on 04/03/2021 10:38:34

Edited By br on 04/03/2021 10:40:13

duncan webster04/03/2021 11:21:48
3130 forum posts
52 photos

I've used loctite to extend drills many times, turn the drill shank down and drill a hole in the end of the extension bar. Just make sure it doesn't get too hot or the loctite gives up. Avoids any issues of heat affecting the hard bits

Edited By duncan webster on 04/03/2021 11:22:01

mechman4804/03/2021 12:15:11
2886 forum posts
449 photos

Dependent on dia' ensure that the ends have a suitable chamfer to enable good filling of joint, e.g. vee or 'J' joint, as in stick welding. In the past I've also used Duncans method, plus using epoxy resin, two part metal filler, whatever is to hand that will give a strong enoigh joint. Where needs must I s'pose.


James Hall 304/03/2021 12:41:22
37 forum posts
8 photos

As a relative newby I may be wrong - but you could drill/tap rod and thread the other piece i.e., as commercially bought extensions for some types of drill. Probably almost as quick as making sockets or whatever and 'gluing', probably quicker than brazing/silver soldering. No worries about heat or insecurities about failure doing it like this and pretty sure that the joint will be concentric.

Dave Smith 1404/03/2021 13:02:36
162 forum posts
25 photos

I regularly make up extended drills, I normally silver solder them. I also do the same with sockets also reducing the diameter of them. For these I normally silicon braze as its cheaper.


JasonB04/03/2021 13:13:42
20250 forum posts
2207 photos
1 articles

Silver soldering works well as would buying 1m lengths of silver steel which are easy enough to get hold of in the UK

Jeff Dayman04/03/2021 14:23:33
2121 forum posts
45 photos

+1 for Dave's suggestion of silicon braze or bronze welding / brazing as it is called locally to reduce costs vs silver soldering (silver solder is extremely costly here). I've made a number of extended drills just using mild steel rod with a drilled hole to fit a twist drill, later bronze welded in place. Cheap fast and it works. By using a drilled hole in the rod the twist drill self aligns for the bronze welding.

Bo'sun04/03/2021 15:01:58
390 forum posts

I'd go for 1m lengths as Jason suggests. No worries then about alignment and joint strength. Yes, cost may be a consideration, but better safe than sorry in my book.

Dave Halford04/03/2021 15:23:09
1388 forum posts
12 photos

Perhaps I'm being a bit thick, but what about clearance?

The hole must be more than 250mm deep (allowing 50mm for the drill chuck to hold.) Wouldn't say 50mm of sliver steel the right size for the hole drilled for a narrower length of of round stock to drive it have a lot less friction?

Edited By Dave Halford on 04/03/2021 15:23:45

JasonB04/03/2021 15:42:49
20250 forum posts
2207 photos
1 articles

Gun drills that are typically used for deep hole drilling have the shank the same diameter as the head to help keep it lined up and prevent wandering.

Calum Galleitch06/03/2021 22:10:49
24 forum posts

Thanks all, and sorry for the slow reply. Epoxy does make sense (I neglected to mention I'm drilling wood).

1m lengths would be ideal, and what I normally use, but 11/64" is according to my supplier "obsolete", which rather has me scratching my head, but never mind.

Gun drills would be ideal, but very much in the future!

donkey06/03/2021 23:14:14
74 forum posts
5 photos

when I was an apprentice in 1976 I made extension allen keys about 18 inches long, small allen keys were inserted into holes drilled into the silver steel and all was well however the 8 mm allen key was arc welded to a silver steel rod with an electrode for joining dissimilar metals it was a 680s rod which may now be known by a different name or number. I never thought that the allen key would hold up to the abuse and over tightening that I put it through but it is still in one piece today. no heat treatment was used afterwards so maybe butt weld using a stainless to steel rod of some type.


Dave S07/03/2021 08:11:50
91 forum posts

You don’t say who your supplier is, but I would call Coventry Grinders.


Says they do none standard sizes.


Calum Galleitch07/03/2021 19:19:23
24 forum posts

Dave, yes, they're very happy to get their manufacturer (they don't grind themselves, which came as a surprise) to make it up for me, if I can commit to taking around five hundred metres of it. Bit much for my little operation.

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