Broken Tip R Iles Mortise Chisel

[David Eisenhauer]

I was chopping 1/4" wide x 3/4" deep mortises in some pecan (hard) and broke the tip off on my 1/4" Ray Iles chisel on the beginning of the 2nd pass through the 8th mortise I worked on for this project. The tip broke off when I levered back to eject the debris after the mallet strikes and looks like I broke the last 3/16" - 1/4" off of the length. My first pass yielded an approx. 1/4" deep mortise as I don't normally try to drive a chisel as deep as it can go, just tend to strike the chisel with two solid blows (using a 20 oz Wood Is Good mallet) per movement every time. This pass was probably going to yield another 1/4" of depth (see the "hole in photo 2 where I was able to extract the tip from). This pecan is hard, maybe I struck the chisel a little harder than I normally do? Maybe there was a hard(er) spot in the timber?, maybe I powered up on the lever jerk more than usual? (pretty sure this was not the case this time and the "pop" of the break occurred immediately after just starting my first lever pull). Maybe there was some type of minor flaw in the metal? Who knows, I don't have any magnification equipment to take a close look at it and most likely would not know what I was looking at any way. The end of the remaining chisel is approx. 1/8" thick (doesn't sound like a lot, does it) but this will require an amount of grinding to bring it back down to a useful thickness for final hand sharpening. This chisel is only a couple of years old, not much use to date, but used enough to have honed the working tip at my version of a 35 deg angle many times on a couple-three projects. Chisel 3.jpgChisel 2.jpgChisel 1.jpg

[Pat Barry]

Time to put the grinder to work

[Phil Gaudio]

I had the same experience: very nice chisels, but poor choice of steel.

[ken hatch]

I was chopping 1/4" wide x 3/4" deep mortises in some pecan (hard) and broke the tip off on my 1/4" Ray Iles chisel on the beginning of the 2nd pass through the 8th mortise I worked on for this project. The tip broke off when I levered back to eject the debris after the mallet strikes and looks like I broke the last 3/16" - 1/4" off of the length. My first pass yielded an approx. 1/4" deep mortise as I don't normally try to drive a chisel as deep as it can go, just tend to strike the chisel with two solid blows (using a 20 oz Wood Is Good mallet) per movement every time. This pass was probably going to yield another 1/4" of depth (see the "hole in photo 2 where I was able to extract the tip from). This pecan is hard, maybe I struck the chisel a little harder than I normally do? Maybe there was a hard(er) spot in the timber?, maybe I powered up on the lever jerk more than usual? (pretty sure this was not the case this time and the "pop" of the break occurred immediately after just starting my first lever pull). Maybe there was some type of minor flaw in the metal? Who knows, I don't have any magnification equipment to take a close look at it and most likely would not know what I was looking at any way. The end of the remaining chisel is approx. 1/8" thick (doesn't sound like a lot, does it) but this will require an amount of grinding to bring it back down to a useful thickness for final hand sharpening. This chisel is only a couple of years old, not much use to date, but used enough to have honed the working tip at my version of a 35 deg angle many times on a couple-three projects. Chisel 3.jpgChisel 2.jpgChisel 1.jpg

David,

Look at the break, if there is an area of dull gray it will indicate a fault in the steel. Stuff happens. If not, but I expect you will see a old fault, then I'd look at how I was using the chisel. BTW, I'd contact TFWW if I found an area with a fault, I expect they would like to know about it and from my experience working with TFWW they will replace your chisel even if there is not a fault in the steel.

ken

[ken hatch]

I had the same experience: very nice chisels, but poor choice of steel.

Care to tell us more?

ken

[Larry Frank]

How would someone know if it was a bad choice of steel without knowing the grade, chemistry and heat treatment. I could break the tip of almost any chisel in that way.

By the way, I am a metallurgical engineer so I have some basis for my comments.

[Pete Taran]

A more accurate statement might be great choice of steel, but poor heat treating.

[Brian Holcombe]

I think an adjustment if technique is needed for this material. I don’t lever but instead chop the waste with another round of chopping before lifting the waste out. You might try something similar when working in pecan.

[Larry Frank]

I think it is impossible at this point to say either poor steel or heat treatment. Most of these steels have a hardness in the upper 50s or higher. Since sharpness and maintaining a sharp edge is important, there is less ductility. Bending them like the OP did put very high stress on them and a brittle fracture happens.

Think about what would happen if you stuck 3/16 - 1/4" of your 1/4" wide chisel into a vise and then pulled back on the chisel. Most likely the tip would break off.

Before anyone makes guesses, it would be great to see a close up of the fracture surface. To really find out what happened, you would need several metallurgical tests.

[Pete Taran]

Larry, I’m pretty sure if you took a piece of hardened steel and clamped it in a vise and bent it, it would break. But that’s not what the OP was doing, he was using a mortise chisel to chop a mortise in wood, the exact purpose it was designed for. I’ve never worked in pecan, but I’ve chopped tons of mortises in hard maple with no damage. If the chisel failed using it for what it was designed for, then I’m putting my money on the tool, not the user.

[Phil Gaudio]

Sure: these were made of D2. I suspect if they had chosen A2 (or O1) which exhibit better toughness, these fractures would not happen. I've seen these metallurgical discussions go down hill fast (sort of like a sharpening thread), so I am not going to bother posting graphs, etc. At the time my chisel fractured, I did a brief search and found a number of similar incidents with the RI chisels. As I said: nice chisels with a great design, but poor choice of steel.

[Patrick Chase]

How would someone know if it was a bad choice of steel without knowing the grade, chemistry and heat treatment. I could break the tip of almost any chisel in that way.

By the way, I am a metallurgical engineer so I have some basis for my comments.

Those specific chisels are D2, though Iles doesn't specify hardness/tempering. I suspect based on comparison to other tools with similar steels that they're around Rc61-62. D2 is commonly used for punch and die work, so I don't think that it's fair to describe it as a poor or unusual choice for an application like a mortise chisel.

Note also that PM-V11's apparent creator has stated that "it can be considered ... a corrosion-resistant D2 tool steel", and Veritas uses it in their mortise chisels, so RI's choice isn't terribly unusual.

A more accurate statement might be great choice of steel, but poor heat treating.

Quite possible, but I don't think the OP has provided enough data to make that call. Certainly something went wrong, probably in fabrication/treatment.

[Stewie Simpson]

Alarm bells should be ringing;

The primary bevel on the chisel is ground to a very narrow 20 degree angle. This of course is not a strong enough angle to hold up to vicious chopping, but it's historically accurate because the narrow angle lets a blow on the chisel push the chisel very deep. And that's what we want - to go as deep as possible with each blow. But of course we have to strengthen the tip or it will bend. So mortise chisels need a hefty secondary bevel at the tip or around 35 degrees. It turns out with D2 steel (see below) we can use a very tiny secondary bevel. It works great and it reinforces the shallowness of the primary angle so these chisels can get even deeper per blow than the old antiques. All you need is a tiny secondary bevel, even a 1/16" is fine. In general we recommend that when you sharpen just sharpen the secondary bevel and it will grow wider. If it gets annoyingly wide just regrind the primary bevel at 20 degrees.

https://www.toolsforworkingwood.com/...ls_by_Ray_Iles

[Larry Frank]

When one breaks or damages a tool, the first response typically is to blame the tool rather than the user.

Stewie has pointed out that the 20 degree angle is very narrow. Along with the width of the chisel, there is not much support for the tip. If you embed the tip in hard wood and bend the chisel much the tip could fracture.

Without much more information, it is difficult to blame either a mfg defect (wrong steel grade or heat treatment) or user technique.

[Pat Barry]

It wouldn't be surprising to have the combination of levering the tip back and forth repeatedly in hard wood such as this to cause local work hardening of the steel and subsequently resulting in fracture.