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chisel explosion??

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Forum topic by planeBill posted 07-02-2012 12:39 PM 888 views 0 times favorited 8 replies Add to Favorites Watch
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planeBill

480 posts in 1065 days


07-02-2012 12:39 PM

I have never seen anything like this before, have you? I was chopping out a fingerjoint type joint in some QSWO I was going to use to make a small-ish tool chest. I was using an old stanley 750 3/4 chisel that, while I’ll admit had some very minor pitting, but otherwise in very nice condition. Force was provided by a, what I would consider, my small white oak mallet. One hit, straight down, not a homerun swing but I had to put a little something into it, it is QSWO. The tip of the chisel about 3/4” up gave a loud gunshot like sound and seperated from the rest of the chisel remaining perfectly vertical in the joint. A beautifully clean break, straight across the blade. WTH??!!

-- I was born at a very young age, as I grew up, I got older.


8 replies so far

View jmos's profile

jmos

681 posts in 1026 days


#1 posted 07-02-2012 01:22 PM

Sounds to me like it was already partly fractured, and the blow was enough to make it let go. But, No, I’ve never heard of anything like that before. Glad you weren’t hurt! If you had been holding the chisel low by the blade it could have been ugly.

-- John

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Bluepine38

2876 posts in 1741 days


#2 posted 07-02-2012 01:40 PM

Since it is an old chisel, there have probably been times when it was used to lever some wood out of the
cut being made. That could have started a stress fracture that got worse over time, or there could have
been a fault in the chisel from the beginning, if you have a master blacksmith near you, they might be able
to give you an answer. I repeat John’s message, glad you were not hurt.

-- As ever, Gus-the 75 yr young apprentice carpenter

View Brett's profile

Brett

621 posts in 1339 days


#3 posted 07-02-2012 11:07 PM

Just like a baseball player who pulls a hamstring while “just jogging through the outfield”, usually the damage started long before and what appears to be an insufficient cause is just the proverbial straw that breaks the camel’s back.

-- More tools, fewer machines.

View JJohnston's profile

JJohnston

1578 posts in 1947 days


#4 posted 07-02-2012 11:26 PM

Can you take pictures? Can you describe the appearance of the broken surfaces? Usually, “old break” looks different than “new break”, so if it had been cracked for a long time, you can tell.

The break goes straight across? Is it perpendicular to the blade in every plane (side to side and front to back), or is it straight in one direction and angled in another?

-- "Sorry I'm late. Somebody tampered with my brakes." "You should have been early, then."

View planeBill's profile

planeBill

480 posts in 1065 days


#5 posted 07-03-2012 12:20 AM

After a thorough cleaning and tuning of it I really didnt see anything indicating abuse or a break or fracture. Not to say I could have seen a microscopic but there was nothing glaring. It did indeed break in a very symetrical manner, straight acrossthe width and thickness or side to side and front to back.
I’ll try to post from my phone it may or may not work. It definitely looked new to me and the dark area on the pic is from where I rubbed my thumb across it staring in amazement.


Like I said the discoloration was not there until I touched it. I all looked very fresh but I have never seen this before so I really dont know

-- I was born at a very young age, as I grew up, I got older.

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ksSlim

984 posts in 1546 days


#6 posted 07-03-2012 02:49 AM

Looks like a quench break, happens on iron/steel that has been heated and quenched (quickly cooled) and not properly tempered. Never seen it on an older chisel but have seen it in amatuer or new smiths makeing hot chisels or punches.

-- Sawdust and shavings are therapeutic

View planeBill's profile

planeBill

480 posts in 1065 days


#7 posted 07-03-2012 01:30 PM

Did you notice how shiney and flat I had the back of that thing? I put a lot of work into that one. ^&%&# :)
Thanks for the thoughts on this. I didn’t have to regrind this one, maybe the former owner? Would this have to be done during manufacture or could this have been caused at a later time? The getting too hot and quick cooling I mean.

-- I was born at a very young age, as I grew up, I got older.

View Oldelm's profile

Oldelm

75 posts in 831 days


#8 posted 07-03-2012 02:02 PM

Happy you did not get injured. I believe I have done this to myself years ago. I had no idea about steel properties and would grind cold chisels until super red hot and the quench in water. I had no idea what I was doing I had just seen others quench things. Take one of those and apply it to some metal with a heavy ball peen and just shatter the edge. Only later did I learn a little more about heating steel. Now I am just plain dangerous so I stick with the stones.

-- Jim, Missouri

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