First Catastrophic Failure...

CDHumiston

CDHumiston

KNIFE MAKER
This blade came out of heat treat and temper warped. It measured at 61HRC. I made my first attempt at straitening with my Carbide tipped hammer.

Not sure if I was hitting it too hard or if my temper was off and it was brittle? Anyhow...I have my first broken blade.

The heat treat looks good to me. Anyone see an issue?20220619_112012.jpg
 
Seriously, though. Probably just hit it too hard. How well was the blade supported where you hit it?

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Are those marks where the hammer struck, Chris? Looks like the blade cracked along a line of those marks. What does the geometry of your carbide point look like?
 
What part of the blade is the break in? That hole makes it look like the tang area? Are those "dimples" from the carbide hammer? If so, and they're as deep as they look -that would be some pretty hard hits. How about a photo of total blade, both pieces laid together?
 
To try and answer all the questions...

It is broken. I may have hammered too hard...

The marks are hammer strikes and I have come to find out, on the wrong side. Picture of the hammer posted.

The break is right near where the handle comes into the blade. Hammer is 7oz small ball peen with a rounded carbide insert.

Pictures...

20220619_163022.jpg20220619_163031.jpg20220619_163054.jpg
 
CDHumiston said:
To try and answer all the questions...

It is broken. I may have hammered too hard...

The marks are hammer strikes and I have come to find out, on the wrong side. Picture of the hammer posted.

The break is right near where the handle comes into the blade. Hammer is 7oz small ball peen with a rounded carbide insert.

Pictures...

View attachment 81069View attachment 81070View attachment 81071
Click to expand...

Is that a Vaughan hammer?

I like Vaughan. My first framing hammer was a Vaughan... :)

I didn't realize those carbide hammers are that light.

I'd you stick the two pieces back together look for any small defects on the edges, ESPECIALLY on the corners, where the crack could have started.

My thinking is that there was a small defect (deep scratch or knick on the edge) and by tapping with a carbide hammer you sort of chased the crack inward.

Like cutting a brick with a chisel.

Edit: Propagate. Using big words make you sound like you know what yer talkin' 'bout.

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The guy in this video seems to be beating the blade much harder than I was. My steel started out as .082 thick though...

 
Chris, just how deep are the divots where you hit with hammer?

My understanding of how this works is the divots actually stretch the metal a tad causing the blade to straighten out. Remember, you're hitting the concave side, so as small divots form it stretches the metal causing the blade ends to lay down as the blade becomes straighter.
 
KenH said:
Chris, just how deep are the divots where you hit with hammer?

My understanding of how this works is the divots actually stretch the metal a tad causing the blade to straighten out. Remember, you're hitting the concave side, so as small divots form it stretches the metal causing the blade ends to lay down as the blade becomes straighter.
Click to expand...

First problem was I was hitting the convex side...

My divots were not very deep. I think there was a flaw in my blade or something. Or the fact I was hitting the wrong side...
 
Some of your hammer marks show a bright spot or darker spot dead in the middle of the mark, so there may be a sharper point on the tip of carbide? My carbide tipped hammer leave sort of an oval mark on the steel and is smaller and not as deep.
 
OK, I thought the divots might not be as deep as they looked. Hitting from convex side surely could cause the break - it's bending with every strike of hammer. It's my understanding the place the carbide hits should be solid against a solid surface so the impact is localized at the divot causing the metal to expand allowing the blade to lay flat.

Here's the HF hammer I used to make the straightening hammer:
www.harborfreight.com

8 oz. Stubby Ball Peen Hammer

Amazing deals on this 8Oz Stubby Ball Peen Hammer at Harbor Freight. Quality tools & low prices.
www.harborfreight.com www.harborfreight.com
I drilled a 1/4" hole in the flat (hammer) side and silver soldered a broken 1/4" endmill shaft (or drill bit?) that I had rounded off in the grinder. Put carbide shaft in handdrill and spin while grinding on grinder does a good job of making a nice round tip.
 
Last edited:
KenH said:
OK, I thought the divots might not be as deep as they looked. Hitting from convex side surely could cause the break - it's bending with every strike of hammer. It's my understanding the place the carbide hits should be solid against a solid surface so the impact is localized at the divot causing the metal to expand allowing the blade to lay flat.

Here's the HF hammer I used to make the straightening hammer:
www.harborfreight.com

8 oz. Stubby Ball Peen Hammer

Amazing deals on this 8Oz Stubby Ball Peen Hammer at Harbor Freight. Quality tools & low prices.
www.harborfreight.com www.harborfreight.com
I drilled a 1/4" hole in the flat (hammer) side and silver soldered a broken 1/4" endmill shaft (or drill bit?) that I had rounded off in the grinder. Put carbide shaft in handdrill and spin while grinding on grinder does a good job of making a nice round tip.
Click to expand...

I have 3 different carbide tips that I ordered a while back. My drill press is coming tomorrow so I'll be able to get a proper hole in the hammer head. Now I just need to go buy a few hammers...
 
Chris: Depending on the hammer you get the head could be pretty hard about drilling. The hammer I linked to was hard, even tried a carbide drill bit to drill hole. Seems like I finished the hole with a HSS bit, but really dulled bit with the drilling.

Owl: I really like your tag line: "Giving money and power to the government is like giving whiskey and car keys to teenage boys" I might add "girls" in that mix since my oldest daughter was quite "adventurous".
 
I used a carbide bit to drill the hammer head, then ground the flat end to the shape I wanted, snapped it off at the flutes and stuck it into the same hole that the bit drilled into the hammer. Didn't even need to use epoxy, nice tight fit!
 
I don't think it'd be detrimental to anneal the hammer head, drill the pocket for the carbide insert, braze or silver solder it in place, and while the head is still hot quench it, then temper it back to a bit. Maybe a dark straw color.

The annealing process is pretty well hands-off if you use an HT oven and it'll save you from a lot of frustration and twist drill sharpening. Brazing, quench & temper shouldn't take but 20 minutes.
5fcc18c94899fc9cee53bfe1ba24db27.jpg
d3552a8cfe43f9c5d26f0ddcd2fc39e1.jpg


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