Broken Tip R Iles Mortise Chisel

[Phil Gaudio]

These pics were still in my photobucket account:

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This was cherry, and I had just started working on this mortise. I do recall it did take a while to extricate the errant tip, but I did salvage the mortise. The chisel: not so much.

[michael langman]

Using D2 in forging,punching applications, we always had it double and even triple tempered because it was needed to prevent fracturing under stress.
Maybe Isles doesn't know that.

[michael langman]

Also D2 does not have the toughness of other steels so it is more prone to fracturing under stress, especially with such a small cross section as the tip of that chisel.

[michael langman]

Although S7 tool steel would not hold an edge as long as A or D series steels it would hold up well under the strain of leverage. Easy to sharpen.
I don't know why it isn't used more in wood tools.

[David Eisenhauer]

Just re logged back in and read all of your comments - thanks for the responses, but, for my own taste, I tend to fall more into Ken's line of "stuff happens". I have used the same mortising technique since the 1980's or so (albeit not at all in an all day-everyday situation at all) and have been working my way through way too much left over pecan from a partially aborted commercial cabinetry job from several years ago, but the use of this particular chisel is the new (so to speak) part of the equation. My initial, on-the-spot reaction to the incident was that something was "brittle" because I really just had started my lever pull. I position the tip, two strikes, then one lever pull (push away actually) to loosen the debris and move the tip ahead for the next go around. I don't pry back and forth, don't try to achieve maximum depth per mallet blow. I re hand sharpen the tip at a 35 deg angle any time I feel like it will benefit the operation and don't use dull chisels. Previous to acquiring the Ray Iles chisel, I used a Sorby registered type firmer chisel for many, many years and have been getting used to the differences between the two chisels. I have had the feeling that the Ray Iles chisel was quite a bit beefier in general than the Sorby (Sorby is much more flexible in the 1/4" size) and, with the meat of the Ray Iles chisel running "north-south" in the mortise, felt that it was a more robust chisel although (to my hands) a more "club like" or not as user friendly chisel when first picking it up. I used the Sorby to clear out the broken tip and finish the mortise I was working on and noticed that I tended to pay closer attention to the lever operation than I had been with the Ray Iles. More attention due to the recent breakage or more attention because the Sorby is a different chisel? Don't know. I stand by my initial assessment in the original post - who knows why it broke, but I will grind and re sharpen the broken end for continued use. I will try out Brian's suggestion of a double chop pass before starting to clear (lever) the debris out if I can break myself of 20-30 years habits (I tend to get into a "zone-mode" when chopping mortises) and see how that goes. I'm thinking if it is good for Brian, it might be good enough for me. If I break it again, I will probably discontinue use of the chisel. Actually, the larger question remains - is this incident worthy of promoting a CBN grinder wheel purchase? What say you Derek?

[Patrick Chase]

IMO mortising chisels and wheel grinders don't mix very well. The last thing you want is to be levering on a concave bevel, such that the bevel angle closest to the edge is even less than the average (20 deg in your case).

I use CBN wheels on most of my tools, but the mortise chisels only see belts and flat diamond disc grinders (mostly the latter nowdays).

[David Eisenhauer]

I will use the grinder to get some of the now-way-too-thick end off (of the 20 deg face) before using sandpaper-rough diamond-800/1,000/6,000/13,000 water stones to shape and then hone the final working end of the chisel. You did not answer the most important question, though - does this event warrant a CBN wheel purchase? And if not, what do I have to do to justify a CBN wheel purchase?

[Pat Barry]

I will use the grinder to get some of the now-way-too-thick end off (of the 20 deg face) before using sandpaper-rough diamond-800/1,000/6,000/13,000 water stones to shape and then hone the final working end of the chisel. You did not answer the most important question, though - does this event warrant a CBN wheel purchase? And if not, what do I have to do to justify a CBN wheel purchase?

It all depends on who the decision maker is and what your track record is with previous purchase decisions.

[Patrick Chase]

Back to the topic of geometry, I've always used 20 deg primary bevels on my mortise chisels (initially Narex, now a mix of RI and LV), though with a 35+ degree secondary bevel about 1-2 mm tall at the tip. I have never had issues with fracture, though I also treat levering as a (sometimes very) necessary evil rather than as a "go-to" means of material removal.

More broadly I think that the faster/easier chopping one gets with a 20 deg primary is worth having to take a little care.

I also think that the OP should get in touch with TFWW (assuming they were the source of the chisel). That doesn't look like an expected failure mode to me, and I suspect Joel will make it right unless there's clear evidence of abuse.

[ken hatch]

I will use the grinder to get some of the now-way-too-thick end off (of the 20 deg face) before using sandpaper-rough diamond-800/1,000/6,000/13,000 water stones to shape and then hone the final working end of the chisel. You did not answer the most important question, though - does this event warrant a CBN wheel purchase? And if not, what do I have to do to justify a CBN wheel purchase?

David,

You should know by now, never pass up an excuse to buy a tool no matter how weak .

One of the things usually missed on the TFWW blurb about RI chisels is putting a convex bevel on the chisels. Back in the day it was common for mortise chisels to have a convex secondary bevel. I think it makes a stronger chisel and makes it easier to lever.

ken

[Nicholas Lawrence]

For whatever it is worth, I have two antique mortise chisels. One is a 3/8 Sorby. The other is a 3/16 I. Sorby. Both are ground at approximately 30 degrees. I say approximately because both have a convex bevel. It is very slight, and I had never noticed it before putting the protractor on it, but it is definitely there. Neither is anything close to 20 degrees. I have used them both quite a lot, and they work very well.

[Jerry Olexa]

Time to head to the grinder methinks.

[Roger Nair]

David, I suggest that the whole discussion on metallurgy is a mute point since it's the chisel in hand that has failed. The corrective measures should be geared towards your most severe service the chisel must perform. Since the original profile has failed, I would alter towards blunter angles. If you can, I would increase the primary bevel by 5 degrees and have a secondary bevel at least 5 degrees more. A rounded secondary bevel heel seems likely to increase strength at the tip by giving a gradual path for stress to be relieved. I would not hollow grind the finished profile.

If pry and scrape is a desired chisel function, get a lock mortise chisel or a swan neck chisel. Save the mortise chisel for chop and counter-chop and chip clearance.

[Patrick Chase]

David, I suggest that the whole discussion on metallurgy is a mute point since it's the chisel in hand that has failed. The corrective measures should be geared towards your most severe service the chisel must perform.

Given that this is a $70-ish chisel sold by a dealer who stands by their products, I think that any discussion of topics other than contacting the dealer is moot (not "mute", though I'm continually amazed at how many people mess that up).

[Pat Barry]

Given that this is a $70-ish chisel sold by a dealer who stands by their products, I think that any discussion of topics other than contacting the dealer is moot (not "mute", though I'm continually amazed at how many people mess that up).

Considering that the said chisel was used for quite some time doing mortising work in relatively hard material with some significant levering taking place, I'm not so convinced this was a manufacturing defect at all. Perhaps the supplier will be willing to take it back. If so, it would be interesting to hear back what their findings were regarding this particular breakage.

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.