# Something new in my woodworking--I broke a chisel



## CharlesA (Jun 24, 2013)

I've had a set of Irwin Marples Chisels for about 3 or 4 years. I was chopping some mortises in QSWO tonight, and all of a sudden, the blade was in two pieces, the break an almost perfect perpendicular. Any thoughts?


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## BurlyBob (Mar 13, 2012)

Gotta be some kind of defect in the metal. Was it one of the new and improved chisels from China? Either way that really bites.


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## TheFridge (May 1, 2014)

Sharpen it up and put it back to work.


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## Clarkie (May 11, 2013)

Start using a mortise chisel. rut ro


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## TheWoodenOyster (Feb 6, 2013)

My only thought is that is weird.


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## nailbanger2 (Oct 17, 2009)

My thoughts are you were hitting that poor chisel too hard, Charles. I'm going to have to make some tips out of Charmin for mine, as I have the same kind.


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## Mahdeew (Jul 24, 2013)

The mighty oak can do that.


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## Redoak49 (Dec 15, 2012)

I can guess at the cause if you give a good close up picture of the fracture surface. Also, were there any small nicks on the sides?

When trying to figure out why or how something fractured, a good picture of the fracture face is most important.


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## bearkatwood (Aug 19, 2015)

You are becoming stronger grasshopper.


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## BubbaIBA (Nov 23, 2011)

From the photos and where the break occurred I'm making an assumption that you were "levering" against the back not the bevel edge. I also expect there was a fault in the chisel but without a image of the fracture that is an assumption. Even with a robust mortise chisel like an English pig sticker the levering should use the bevel as the lever point. Using the back will put the stress point higher up the chisel resulting in a longer arm and greater stress at the lever point.

While bevel edge bench chisels can be used for mortices (I will on occasion) a better option is to use a mortice or sash mortice chisel. They have evolved over time for just that job. With a bench chisel you need to take smaller cuts than with a mortise chisel with more room to lever the waste

ken


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## CharlesA (Jun 24, 2013)

I was looking back on why I had decided I didn't really need mortise chisels for my occasional mortise work and came upon an article by no less than Paul Sellers that suggested exactly that. I was cutting one far deeper than usual and started to really yank on that chisel. I finished up with an Aldi chisel I bought as a backup. I immediately noticed that the Aldo blade was thinner and bendier, so to speak.

I already figured it was mostly my fault, but I am surprised that it broke so cleanly.


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## boisdearc (Sep 29, 2014)

I am sure Marples will warranty that…


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## TheGreatJon (Jan 9, 2015)

"Control, control, you must learn control!"


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## HokieKen (Apr 14, 2015)

Look for beech marks on the fracture face. They'll look kinda like growth rings in a tree. If they're there, then there was a weak point in the steel that propogated out over time until the break occurred. If there are no beech marks, it was probably a brittle fracture that occurred suddenly. Either way, I'd think the manufacturer would cover it under warranty. But, if it was a fatigue fracture and has evident beech marks, it was a material flaw and they should most definitely replace it.


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## Sylvain (Jul 23, 2011)

It seems you first drilled a hole before using the chisel, something which is not part of the Paul Sellers method.
I have used the PS method to chop mortises 8 cm deep X 10 mm wide X 6 cm long (in fact 4cm because it was through and I flipped the board) with a no-name beveled chisel, bought a few Euro on a flea market, without any problem.
If you look carefully to the video where he does two mortises behind a glass, one with a mortise chisel and the other with a beveled chisel, you will see that the bevel of the chisel acts as a wedge, producing a shear force which split the wood along the mortise wall. Practically no leverage action is needed; except to clean the waste.
One has also to listen to the sound, the sound changes at the last tap before the next move, don't make an extra whack.


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## JohnChung (Sep 20, 2012)

I would say that the chisel was faulty. If the chisel failed, there would at least be a bend on it first.


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## CharlesA (Jun 24, 2013)

I'm not a Paul Sellers purist. I just followed his advice when he said mortise chisels weren't required. I would have use my mortiser to do at least 90% of it, but these pieces are 6" tall and won't fit in my x-y vise, and I don't want to take it off. I drilled a hole and then chopped out the rest.


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## RHaynes (Dec 18, 2013)

Aren't these chisels made of two kinds of steel? A softer steel for the upper part of the chisel and then harder tool steel brazed on near the tip? Perhaps that is the point where it failed. But from the picture of the mortise you included, it looks like you were chopping pretty deep and levering against a bunch of material. I chop my mortises with bench chisels, and Irwin Marples no less. But ever since seeing the sort of progressive-depth approach taken by Paul Sellers, that's how I do it. So on the deepest chop-at the end furthest from where I start, the material I'm levering against has all been chopped away already. But Irwin does have a lifetime warranty. If it was a defect in the steel, then they'll replace it.


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## CharlesA (Jun 24, 2013)

I wasn't being incredibly careful about a stepped approach, but i was doing something like that. I think in this case I was on my 5th one and getting impatient.


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## CharlesA (Jun 24, 2013)

Oh, and when I used the Aldi chisel, I realized it would bend a bit and I would immediately realize I was torquing it too much. The Irwin never bent-just snapped.


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## pintodeluxe (Sep 12, 2010)

Sounds like a perfect excuse for a hollow chisel mortiser.


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## RHaynes (Dec 18, 2013)

> The Irwin never bent-just snapped.


This is a clear indication that the Irwin chisels are cast and not forged. Cast metal tends to crack when bent more than a few degrees while forged will bend much more before breaking. Casting is a cheaper manufacturing method. That's why good kitchen knives and golf clubs are always forged. The knife will hold an edge longer and the golf club can be bent to correct its loft/lie angle.


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## pintodeluxe (Sep 12, 2010)

Nevermind, sounds like you already have one.


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## Sylvain (Jul 23, 2011)

The Irwin was probably flawed.
Paul Sellers uses mortise chisels when doing big deep mortises (the castle doors). 
In his video he says something like "nobody has bent a chisel using this method". This implies that his advice is valid with this method and also that chisels have been bent with some other methods.
The message is "with this method you don't need mortise chisels to start woodworking".

Always read the small characters.


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## TheFridge (May 1, 2014)

Some Japanese chisels are laminated. Blue steel I think they call it. I'm pretty sure the marples aren't.

The chisel might've been in a bind in the mortise, and snapped when a bit more pressure was put on it.

Edit: I think sellers cut his mortises with the bevel facing out.


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## CharlesA (Jun 24, 2013)

It was a cheap chisel. At some point I'll get better bench chisels and perhaps even some mortising chisels. I had a backup and got it done.


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## Picklehead (Feb 12, 2013)

> Paul Sellers uses mortise chisels when doing big deep mortises (the castle doors).
> In his video he says something like "nobody has bent a chisel using this method".
> - Sylvain


To be fair, Charles didn't *bend *a chisel either.


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## Sylvain (Jul 23, 2011)

That's fair, I have well read the number #19 herebove.

The Irwin chisel didn't give the sensitive feedback given by the Aldi chisel.


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## CharlesA (Jun 24, 2013)

Pics









,bcaxnbz


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## rwe2156 (May 7, 2014)

I respect Paul Sellers but can't figure out why he's got 8 planes on his benchtop but no mortice chisels???


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## mramseyISU (Mar 3, 2014)

> The Irwin never bent-just snapped.
> 
> This is a clear indication that the Irwin chisels are cast and not forged. Cast metal tends to crack when bent more than a few degrees while forged will bend much more before breaking. Casting is a cheaper manufacturing method. That s why good kitchen knives and golf clubs are always forged. The knife will hold an edge longer and the golf club can be bent to correct its loft/lie angle.
> 
> - RHaynes


I don't know that you could say it not bending is a tell-tale sign of it being cast. Could have been a fatigue break from working it back and forth. This is exaggerating it a bit but a good example is taking a wire and bending it back and forth until it breaks. This could be happening at a microscopic level until a small crack develops and gets bigger every time you wiggle the chisel until it fractures. I see this happen with shafts on the pumps we make if you put a big side load on it. Some of our lube pumps get put into large gearboxes to provide lubrication and they get driven by a gear. That gear puts a tremendous amount of side load on the shaft and sometimes they break without ever bending or twisting off all because of fatigue.


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## mramseyISU (Mar 3, 2014)

This spot I've circled make me thing you had a microscopic crack in the chisel. Hard to tell with out getting it magnified more but I'd bet that's what happened.


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## InstantSiv (Jan 12, 2014)

> The Irwin never bent-just snapped.
> 
> This is a clear indication that the Irwin chisels are cast and not forged. Cast metal tends to crack when bent more than a few degrees while forged will bend much more before breaking. Casting is a cheaper manufacturing method. That s why good kitchen knives and golf clubs are always forged. The knife will hold an edge longer and the golf club can be bent to correct its loft/lie angle.
> 
> - RHaynes


From my knife making days… knives(or a tool with a sharpened point/edge) are either forged, stamped/milled from blank, or made similar to how carbide teeth are brazed onto saw blades(although in knife making it's very limited and a fairly new thing.) Casting is not capable of producing a fine enough edge that's durable so it's not done at all unless it's one of those dirt cheap gas station dollar knives.

--

A break like that leads me to believe 3 different causes. Abuse, faulty material and/or heat treatment process(lemon), or faulty material selection and/or heat treatment process. I think it's probably the first two. The last one would only hold water if it's a wider issue but since this seems one off it seems either abuse or a lemon. I would ask them for a replacement.


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## Redoak49 (Dec 15, 2012)

The chisel was not cast but rather made from a hot rolled bar and hot forged into shape. It would be ground, heat treated and finish ground.

The picture is not very clear but the dark spot is clearly a pre-existing crack that happened before the final break. The rest of the structure is a brittle fracture. With the pre-existing crack, it would only take a small bending on it to make the crack run across the chisel. A picture with the fracture face in focus would help more but at this point it is pretty clear what happened. I know that it is difficult to get the fracture face in focus especially with a camera phone.


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## diverlloyd (Apr 25, 2013)

I would say that the heat treat was flawed. The grain structure in the pic looks like it was over hardened and not tempered. That could be the initial quench line. Try to reshape ithe edge of the chisel and let us know how it holds up. I would bet it sharpens easier and doesn't hold the same edge. Irwin has really good customer service. Talk to them and send a pic and they will send a new one to you. I knocked off a quick grip clamp from my bench and it exploded into numerous pieces. So they sent me a whole new one since they didn't offer the end piece as a replacement. Super nice people and they also added in some clamping pads in with the new clamp.


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## bandit571 (Jan 20, 2011)

Happen to have two mortise chisels, one by Butcher, the other by New Haven Edge tool co.. Chopping a few mortises on that Enclosed End Table Project…..the bevel snapped off of the New Haven one. Not a real OMG moment…I just went over, and ground a new bevel, then back to chopping.

Yes, it was a little too deep into the Oak, then the wiggle to remove turned into a "pry". Snap! Dug the tip out, ground a new end…back to work. I really doubt IF i could have returned that chisel as "defective". Operator Error was the cause of mine…YMMV


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## 280305 (Sep 28, 2008)

Wheaties OD.


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## Redoak49 (Dec 15, 2012)

The grain structure in the picture was very typical of a heat treated steel which has been quenched and tempered. The microstructure would be tempered martensite and have that kind of fracture surface.

As mentioned earlier, the dark area is typical of a pre-existing crack. What I can not make out in the picture is if there were also cracks on the edges. Also, on most fracture faces you can see if there are features which show the direction that the fracture went.

If the chisel had been quenched and not tempered (over hardened??), the sharp edge would have been cracking off and the chisel likely would have broken in multiple pieces.


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## mramseyISU (Mar 3, 2014)

The material science knowledge of some of you guys is pretty impressive. I know enough to look at that dark spot and see that it had a crack. I don't know squat about the crystalline structure of the steel.


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## diverlloyd (Apr 25, 2013)

By over hardened I was meaning in that area as in the whole thing was hardened and just the first inch or so was tempered to the specs the company was looking leaving the rest harder then was wanted. it was poor wording on my part. But the flaw is the the main issue and the hardness secondary since it's a chisel the temper would be just enough to keep the edge from being brittle. But the slight difference would make it brittle compounding the issue with the flaw. 
Let us know if you contact them and how the customer service is. I hope you have the same quality I had.


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## CharlesA (Jun 24, 2013)

BTW, I ended up putting a new edge on it. i slowly ground it down with my grinder and then used my Mk II to hone the edge. it's wicked sharp . . . and a little short.


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## splatman (Jul 27, 2014)

> BTW, I ended up putting a new edge on it. i slowly ground it down with my grinder and then used my Mk II to hone the edge. it s wicked sharp . . . and a little short.
> - CharlesA


A case of getting some mileage out of something that is otherwise kaput.
Another example of the same.
Definitely a Good Thing.


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## tyvekboy (Feb 24, 2010)

I think it can be re-ground and re-sharpened.


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## CharlesA (Jun 24, 2013)

Two posts up from yours.


> I think it can be re-ground and re-sharpened.
> 
> - tyvekboy


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## Ocelot (Mar 6, 2011)

I've cropped out part of your image, brightened it and increased contrast.

It's poorly focused, but still I think the guys are right that there was a pre-existing crack on the bevel side.

-Paul


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