Weld broken SDS bit?

At Habitat, we are reinforcing a granite block foundation that requires drilling 34 1-1/8" holes, 28" through. On the LAST hole, with 10" to
go, the bit broke (see link).
The bit is carbide tipped, so I thought the shank would be mild, but mild wouldn't break like that, would it?
If it's not mild, is it weld-able?
If it make a difference, it's used in a rotary hammer, where most of the force is impact.
Thanks, Bob
http://home.comcast.net/~bobengelhardt/20140712_125745.jpg
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Bob Engelhardt wrote:

Did you hit it with a file to see how hard ?
--
Snag



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On 7/12/2014 4:41 PM, Terry Coombs wrote:

I wasn't there when it happened and haven't seen it in person.
I don't know metallurgy, so this is a WAG - could it have work-hardened?
Bob
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On 7/12/2014 3:33 PM, Bob Engelhardt wrote:

Looks like a compression fracture. Like jabbing a toe and the joint buckles...
Steel looks all full in spec. It doesn't look like tensile steel. Mine are SDS+ but are all gray-black in color.
The silver drills - plated to prevent rust - are made for drilling. Not hammer drilling. The Gray tool steel ones are for hammer drilling.
If you were only drilling, the steel fractured due to being 'pinched' in the hole and the drill kept turning.
Martin
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On 7/12/2014 11:18 PM, Martin Eastburn wrote:

This was definitely a hammer drill bit. Actually a rotary-hammer bit.
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On Saturday, July 12, 2014 8:33:58 PM UTC, Bob Engelhardt wrote:

Here is a link to a Lincoln rep talking about using 312 stainless to modify tools.
www.youtube.com/watch?vLytQa4A_HI
312 is what I would try. What the hell do you have to lose? Where are you located and what kind of welder is available?
312 is not cheap, but I have some and will send you some. Email me at
dlcaster57atyahoo.com that is a email address that I do not check very often. And of course change the at to @.
Dan
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On 7/13/2014 9:15 AM, snipped-for-privacy@krl.org wrote:

Dan, thanks for the offer. I have seen the bit and it is clearly tool steel. That being the case, I am not going to try to weld it and chance creating brittleness. I am going to try silver brazing with some 55% silver braze that I have.
Thanks, Bob
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Bob Engelhardt wrote:

They TIG weld 4140 with ER70S2 mild steel filler all the time ... but once you contaminate the weld area with braze that option is off the table .
--
Snag



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On Tuesday, July 15, 2014 2:07:43 AM UTC, Bob Engelhardt wrote:

If that does not work let me know if you want to try some 312 stainless. You would have to grind off all the silver braze, but for welding you would probably have to do a lot of grinding to get ready for welding anyway.
Dan
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I've been watching this thread, and I just don't see the appeal of welding a bit like this. I would be afraid it would just come apart again, and the next time it would be wedged between a fill stone and a piece of rebar so it wouldn't come out of the hole.
That being said, my Makita SDS hammer drill is 18 or 19 years old, and I have never broken a bit in it like you picture/describe. Its been used to drill plenty of stuff. Some of which should have been done with a core drill, but I had to run what I brung. I have broken the carbide tip of one or two bits, and just plane worn out a few tips, but I have to be honest. I don't ever recall twisting one of these bits off. Some of my larger ones are as old as the rotary hammer, and I still use them.
(I also have a heavier Milwakee spline drive that is only a year or two younger than the Makita.)
I'm sorry. I am doing one of those things I hate. Not answering the question you asked, and I am sorry for that, but I would throw the bit away and buy another one.
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On Friday, July 18, 2014 12:24:15 AM UTC, Bob La Londe wrote:

I think the appeal is that it broke with only 10 inches more to drill. So anything that would get 10 more inches drilled is a winner. The second appeal is that it is for Habitat for Humanity. Not an organization with unlimited funds.
Dan
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On 13/07/2014 06:33, Bob Engelhardt wrote:

Can you go to the other side of the block, and measure from the completed holes very carefully to figure out very accurately where this last hole is supposed to come out, and then start drilling from the other side with a shorter drill bit that you do have?
If you have no access to the other side of the block then you still have a problem.
Chris
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Hammerdrill bits and chisels are made from "S" steels. They are extremely resistant to shock. They are air-hardening steels so to weld it you would have to bevel the edges of both sides of the break, preheat both ends to above 700 degF, and weld using a high strength filler. Stainless would be a bad choice here for fracture toughness.
You could stick weld it with 8018 or 9018 rod, or bust the flux off and use either of those as TIG filler.
Keep it hot during the weld process and let it cool slow, buried in powdered lime, ashes, vermiculite or at very least, clean dry sand. You could also roll it up in a piece of Kaowool. You want it to cool down over a few hours if possible.
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Bob, Just throw out thqat junk bit would be my advice.
i

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Thanks for all the replies and suggestions.
I am not going to weld it: I have very little skill as a weldor & Ernie's description of how to do it right is way beyond me.
Another bit has been bought & job finished with it. A very expensive bit for 10" of drilling; the last 1% of the job!
One of the volunteers found a web page of how-to-use masonry bits and we were doing a number of things wrong, in sense of abusing the bit. We deserved to have it break.
Even if I had welded or brazed it, we probably wouldn't have used it because of the risk of it re-breaking in a hole. If I "fix" it, I will keep it for jobs where it can be abandoned if it re-breaks.
As to why I would try: to salvage some value from a very expensive bit and for the challenge of it.
Bob
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On Saturday, July 26, 2014 11:27:08 PM UTC, Bob Engelhardt wrote:

But there is probably someone volunteering at HFH that has the skills and k nowledge.

Bob
My choice would be to weld it. You can start drilling with it and when you get to where the weld is close to the start of the hole, switch to the new bit. That would save some wear and tear on the new drill bit. And you wo uld have it for a proven ready replacement if anything happened to the new drill bit.
Meanwhile why don't you post the URL of the site with the info on masonry d rilling. I don't have any projects in mind that require masonry drilling, but at always open to learning how to do things correctly. Yes it is off topic for a welding group, but not very far off topic.
Some years back I found a pretty big hunk of granite in my yard. And follo wing some things I learned on this newsgroup, I used a weed burner on it, w hich split it into chunks that I could lift. If anyone tries this at home, wear goggles.
Dan
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Some years back I found a pretty big hunk of granite in my yard. And following some things I learned on this newsgroup, I used a weed burner on it, which split it into chunks that I could lift. If anyone tries this at home, wear goggles.
Dan
Did the heating leave a surface like this?
http://en.wikipedia.org/wiki/File:Obelisk2.jpg
-jsw
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On Fri, 1 Aug 2014 12:31:16 -0400, "Jim Wilkins"

It is said that the Egyptians used a method of building a fire on a large stone that they were trying to quarry and after some time pouring water on the heated stone.
--
Cheers,

John B.
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On Friday, August 1, 2014 4:31:16 PM UTC, Jim Wilkins wrote:

Kind of like that. As you might suspect the heat caused the heated area to separate from the main piece. So the pieces coming off were maybe 12 to 1 8 inches in diameter and only an inch or two thick in the middle. But this is as I remember it. And it was a long time ago.
Dan
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On Friday, August 1, 2014 4:31:16 PM UTC, Jim Wilkins wrote:

Kind of like that. As you might suspect the heat caused the heated area to separate from the main piece. So the pieces coming off were maybe 12 to 18 inches in diameter and only an inch or two thick in the middle. But this is as I remember it. And it was a long time ago.
Dan =======================http://en.wikipedia.org/wiki/Obelisk_building_technology_in_ancient_Egypt "No scientific explanation of these scalloped cut marks has ever been published."
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