timber framing chisel with concave blade

[Adam AR Brown]

I just received a new Sorby 1" timber framing chisel from Lee Valley, and I was surprised to see that the back appears to be ground hollow. There is a definite concavity along the length of the blade.

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Is this normal / intentional? Or a manufacturing defect? It seems like it would hinder paring, but maybe it's no big deal. I've never used a framing chisel, so I'm not sure what to expect.

So far no answer from Sorby or Lee Valley.

Thanks,
Adam

[Scott Winners]

I checked my Barr 1.5" and L-N one inch chisels this morning, as well as my vintage 3" slick.

The L-N is flat, the Barr and the slick both have slight convexity rather than concavity.

I am really waiting for Tom King to check in, but I suspect you can learn to use pictured chisel and do perfectly fine work with it.

Shooting for light tight joints on a side table or a blanket chest is not unreasonable, on those you can move the parts around by hand and arm, often without a time crunch.

When you need back and arms, or a block and tackle to move pieces around, you will want enough slop in the individual joints for the last piece to go in under a time crunch on raising day.

A side table and a barn are both put together with M/T joinery, but they are leagues apart in reality.

[Jim Koepke]

Hi Adam and welcome to the Creek.

Hopefully you will get an answer soon from either Sorby or Lee Valley. In the meantime there is this from an old post on the subject of Timber Framing chisels:


Many of these tools have curved backs and they work just fine.

This post was about bevels on the edges, but as posts are wont to do wandered afield > https://sawmillcreek.org/showthread.php?189731

jtk

[Jim Koepke]

When you need back and arms, or a block and tackle to move pieces around, you will want enough slop in the individual joints for the last piece to go in under a time crunch on raising day.

A side table and a barn are both put together with M/T joinery, but they are leagues apart in reality.

An old issue of Fine WoodWorking had a few articles about working with larger timbers. In the article on timber framing it showed a lot of the joinery tools. One was a mallet that had faces that looked to be more than a square foot and a handle about three feet long. The caption said it was for persuading joints to go together.

jtk

[Edward Weber]

I have many heavy firmer and timber framing chisels. Typically, the back will be slightly convex, if anything.
Is the reference table you're using "flat"? Do you have a better surface or straight-edge to check it against?

[Malcolm McLeod]

... it was for persuading joints to go together.

jtk

^ I believe somewhere in this size range they transition from "mallet" to "commander".

So as not to stray too far from OP, I bought a very old, horribly pitted, wreck of a 2" slick (for $10) to do a 1-time bit of timber framing. It was in no way flat or square, the pitting made the back largely concave, and sharpening efforts were only marginally successful. But it got the job done and now hangs on the wall to remind me to be more careful with (used) tool purchases.

...trying to talk myself into grinding the last 2" off length to get a fresh start.

[Adam AR Brown]

I have many heavy firmer and timber framing chisels. Typically, the back will be slightly convex, if anything.
Is the reference table you're using "flat"? Do you have a better surface or straight-edge to check it against?

Yeah, I was a bit thrown - a slightly convex back makes sense to me.

It's not a dead flat surface, but it's flat-ish. It does show the curve in the chisel back faithfully. I can see the concavity of the chisel very clearly by sighting down the blade, I just don't have a great way to take a picture that way. Also, as in the picture the front side of the chisel is flatter than the back so it does seem to be ground that way.

[Adam AR Brown]

I am really waiting for Tom King to check in, but I suspect you can learn to use pictured chisel and do perfectly fine work with it.


Yeah, I'm sure I could. And I'm definitely tempted to just put an edge on it and get to work... Probably some lapping of the front couple inches will help. I'll probably not ever be able to get it really flat though.

My main concern is that it won't be as useful for paring as it might otherwise have been.

[Tom M King]

I went and looked at my two 1-1/2" timber framing chisels. One is an old one, and the other a Barr. Both are pretty flat, and both work well. I had never looked at how flat their backs were before.

I'd exchange it. It probably warped sometime after it was milled.

When I bought my set of Ulmia mortising chisels sometime around 1975, I remember one was warped with a twist. That was before cell phones, and I was nowhere near a phone to call about it, so I just stuck it back in the roll. It must have been a few years later when I had them all out of the roll, and could not find one that was warped or twisted??? They're all still nice and straight to this day.

[Edward Weber]

I would also return it.
It's either ground improperly or not cooled properly after heat treating.

One of the issues is having the cutting edge below the centerline of the tool. This would be prone to dig in's. Slightly convex can be controlled and can have its benefits. Concave, not so much

[Adam AR Brown]

I told the customer support rep at Lee Valley that I asked around and nobody thought the chisel seemed right, so they are sending me a replacement.

Thanks for the feedback everybody!

Looking forward to doing a little small-scale timber framing (a wood shed for starters).

[Rafael Herrera]

The heat treatment can cause the steel to deform, you seem to have gotten one that slipped their QA inspection.

[Jim Koepke]

The heat treatment can cause the steel to deform, you seem to have gotten one that slipped their QA inspection.

One misconception about QA in manufacturing is that each item is individually inspected. Quite often it may be less than 5% of a batch of mass produced products that are actually inspected. Even less may be compared to a gauge. Inspection costs a lot time and effort. On some things even with each item being viewed errors can happen. During my days as a press operator we were supposed to look at every item to make sure it was printing properly. After a few hundred you almost go blind as they pass by at 10 or more a minute. (hand fed silk screen isn't high speed printing)

A lot of the real QA takes place before it even gets to the QA inspector(s). There are test groups in some industries and rework stations in others. During my time as a test technician we often joked about being final assembly. The test department at one job had preliminary test, post burn in testing and then final testing. We still shipped product that really wasn't ready for market.

One such unit would not power up all the time. My discovery was that if this happened all you had to do was switch it of and on quickly and it would come up properly. I mentioned this to a few of the managers, but they didn't think it was a problem. So if it did this during the test sequence all the technicians knew to cycle the switch. A few days later one of the customer service representatives came to me frantically and asked what the trick was when a machine didn't power up properly. After a few days of that the engineers came in to see what the problem was and came up with the fix.

So yep, problem found but it ships anyway. A lot of customers may not complain if there is an easy workaround or they don't notice.

jtk

[Rafael Herrera]

In some industries every item is or must be inspected, I work in one of those industries.

Regarding this chisel, who knows if it even got inspected, so indeed it slipped pass QA.

Here's a story, once I stopped by the warehouse of Tools for Working Wood in NY. I was looking for one of the Ray Iles pig stickers. They didn't have any, but they had some that they had flagged and pulled from the shelf. The handle and the blade were a bit misaligned, nothing major but the sales person knew that it would ge returned if they sold it. They know that a lot of shoppers focus on cosmetic issues more intensely than in actual fitness. They didn't offer a discount, so I didn't buy it. The moral of the story is that someone along the line picked up on a defect (real or not) in the tool and set it aside.

Here's another story, an acquaintance bought a LV shooting plane. It had some indentation on the inner part of the body of the plane, the finish had a small irregularity that had no effect on performance. An irregularity you had to look for to notice. The buyer went back and forth with LV, all their planes had the same irregularity, maybe a mark left when the plane was in production. The buyer was so bothered by it that decided to return the plane and the replacement. I wouldn't view this as a failure of QA, but there's no accounting for what some people will accept or not.

Rafael

[Edward Weber]

I have received 3 turning tools total from 2 different vendors over the years that had a visible bend in them.
Each time I was told that the heat treating, blah, blah, blah. Yeah, I get it, I just want a straight tool. As the retail customer, I should need to listen to why it's bent, just replace it.
They all got replaced, but with different levels of customer service.
It can be frustrating, having to tell the people you just bought from that their product isn't up to par. They don't always receive it that well.
Glad the OP got his situation sorted out.

[Dave Anderson NH]

As an addendum to Jim Koepke's comment about 100% inspection, statistically it is 80% effective in mass produced products.