Monthly Archive for March, 2011

Are fancy chisels worth the money?

Published on March 31, 2011 in Sharpening. 2 Comments Tags: .

Reader Andrew Reynolds posed a question which has probably occurred to many of us, about whether fancy tools are worth it. He asks: “I’ve got a really good set of bench chisels and I am thinking of adding some mortising chisels to the collection. There is a very wide range in price that you can pay – the Lie-Nielsen chisels look great but the price is up there compared to some others I’ve seen. The question is, why the big difference? Are the more expensive chisels really worth the price?”

You pay for two things in fine chisels: steel quality and the heat treating process. Here’s the executive summary.

Quality of steel

Traditionally, chisels have been made from simple tool steels such as O1, which is iron, carbon, and a touch of manganese (to allow the steel to quench adequately in oil). Ron Hock‘s excellent book, The Perfect Edge, has a great explanation of the subject for those who want more depth. These steels have good hardness and abrasion resistance, but yield readily to sharpening stones. Their fine grain structure lets them take a very keen edge.

Steel design is a trade-off. Metallurgists can make alloy steels such as A2, which is harder and more wear resistant than O1, by adding chromium, nickel, manganese, and other elements. The chromium is the key here, as it combines with carbon during heat treating to form very hard granules of chromium carbide. These, suspended in a matrix of softer tool steel, give A2 tools their long-lasting edges.

But there’s a price for everything. Those carbides are large and HARD. They don’t grind readily, making sharpening a chore. What takes a minute with O1 tools takes lots of time with A2. If you stop too soon, you leave an edge with a radius approximating the radius of a carbide crystal. It’s not sharp. Also, those tiny carbides can become dislodged from the softer steel at the cutting edge, like stones from concrete, leaving little gaps. So we compensate by leaving more steel at the edge for them to hang on to, by grinding at a larger angle. That makes the edge last longer (it would with O1 also), but also makes the tool harder to push through the wood.

Heat treating

You harden steel by first heating it above the critical temperature (around 1400ºF), so the carbon and other elements go into solution in the still solid steel. Then you cool it quickly (“quenching”), freezing the molecules into a crystal structure called Martensite. The faster you cool the steel, the higher the percentage of Martensite versus other, softer crystal structures. But if you quench too fast, you crack the steel. If you quench, then cryogenically cool the steel with liquid nitrogen, you can convert more of the original structure to Martensite, getting a more durable edge. Next, you reheat the steel to 350–400ºF and cool it slowly, “tempering” it and converting some of the very brittle steel structure to a softer, tougher matrix that won’t shatter when it encounters a knot or gets dropped on the bench.

That heat treating takes time, fancy ovens with inert atmospheres, and cryogenic freezers; all of which cost money. And it pays off best with fancier steels such as A2. So a 1/2″ rod of hardened A2 is $6.50/ft. versus $2.50/ft. for O1.

The bottom line

Which is better? I enjoy sharpening, and like an edge I can shave with. Most of my hand chisel work is paring. So I like O1 tools that are easy to hone and sharper than a witch’s curse. If I’m buying woodturning tools, which don’t have to be so sharp but do have to withstand abrasion and heat, I’ll go for alloy steels such as A2 or M2. But if you’re someone who puts off sharpening as long as possible and then doesn’t mind devoting a lot of time to it, A2 is a fine choice. However, you’ll pay more and may wind up with a less sharp (but longer lasting) edge.

Chisels, grinding angles, and other ponderables

Published on March 16, 2011 in Reviews. 1 Comment Tags: .

Woodriver Bench Chisels

Woodworking buddy and renaissance man Julien LeComte recently sent me a review of his new set of Woodriver bench chisels, and it brought up an issue many of us confront when we decide how to sharpen our blades. Here’s what Julien said:

“I have been putting my WoodRiver chisels to the test while practicing my hand-cut mortise and tenon joinery on some soft hardwood (poplar). Unfortunately, since this is my first real chisel set, I don’t have anything to compare them to. I remove most of the material from the mortise using a drill press, but there is still quite a bit of chopping left to do, and cleaning the bottom of the mortise seems to be very taxing on the edge. I used a 1/4″ and a 1″ chisel to make those joints. I like my chisels very sharp, and I have been resharpening them after completing 2 full mortise and tenon joints. After 2 joints, I usually notice a significant burr on the back of the 1/4″ chisel, which I have to remove using my 1000 grit stone (so I don’t dig a trench into the surface of my finer stones). After that, using a jig to set the honing angle, I resharpen the 2 chisels using a 4000/8000 grit combination stone in a matter of minutes. When I’m done for the evening, and after resharpening, I lightly oil them and place them back on a rack where their Bubinga handle really stands out! So far, I am pretty happy with them.”

Julien mentions that the edges don’t last, but that’s not really the chisel’s fault. Here’s the root of the problem.

Lie-Nielsen mortising chisels

The Wood River chisels are really paring chisels, intended for use with hand pressure or very light mallet taps. If you’re really chopping out mortises, it’s better to use something heavier, such as these Mortising chisels. They have a lot more beef in the shank, to support the heavy forces of mortising. These forces come not just from pounding the chisel down into the wood, but from the levering action one uses to pry the chip away.

If you look closely at the two sets of chisels, you’ll see that the grinding angle of the paring chisels is much smaller than for the mortising chisels—probably 25º compared to 45º. This makes the paring chisels cut with much less effort, but it also means the edges will crumble long before the ones on the mortising chisels do. That’s what Julien’s feeling as the burr on the back of the chisel after cutting a couple mortises. The edge has just bent right back.

So what to do? If mortising is the primary job, try regrinding a chisel to a larger included angle. You’ll find the edge lasts much longer, but it will be harder to use for hand-paring a joint. If you think you’re going to do a lot of this, it might be worthwhile to invest in a mortising chisel or two in the sizes you use most often.

Finishing and using the pin chuck

Published on March 7, 2011 in Jigs and Fixtures, Machines and Woodturning. 1 Comment Tags: , .

Grinding the flat

Once the shaft slid smoothly into a 7mm pen barrel, it was time to cut a flat for the locking pin. I clamped the shaft in a vise and removed most of the metal with a grindstone in a Dremel rotary tool. Just as in hand sharpening, I locked my arms to my body, then used my legs to traverse the tool back and forth, about 75% of the way along the shaft. I got a fairly even cut.

The shaft, with its locking nail

Once I’d removed about a third of the diameter of the shaft with the grinder, I filed the cut flat. For this job I used a 10″ single-cut mill file. File teeth are graded relative to the length of the file, so a fine-tooth 10″ file has smaller teeth than a fine-tooth 12″ file, and leaves a nicer finish. A double-cut file cuts faster, but rougher. About 15 minutes of work got me a relatively flat surface along most of the shaft, as you see at left.

The nail I’d originally selected as a locking pin proved too large, so I used a #4 finishing nail instead, nipping off its head first. Here is the complete tool, almost ready for use.

Magnetizing

I say “almost” because, if your shop is like mine, having a little loose part such as the pin is a recipe for grief. It’ll get lost in no time, probably falling into the chips under the lathe the first time I pull a pen blank off it. So I ran the pin and shaft through a magnetizer. It doesn’t make them grip tightly—the pin can still roll so it locks, but it keeps the nail from sliding off the shaft.

In use

Here’s the new pin chuck in use. I held it in a Beale collet chuck (they have less runout than scroll chucks or Jacobs chucks), slid the desk pen blank on, and twisted it to lock it in place. I brought up the tailstock to stabilize things for most of the turning, parted off at the end of the bead, and pulled the tailstock out of the way to clean up and sand the part. It worked like a charm.

Tuning up a tablesaw

Published on March 5, 2011 in News. 4 Comments

Woodworker’s Journal has a nice article on Tuning up a table saw.

There are some clever approaches that mostly eliminate the need for precision measuring tools. If you’ve noticed burned edges or binding boards during ripping, you’ll find likely solutions here. I recommend checking it out at the link above.

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A pin chuck for desk pens

Published on March 3, 2011 in Jigs and Fixtures and Woodturning. Closed Tags: , .

The parts of a pin chuck

I was asked to turn a couple desk pens for people to use as they signed the guestbook at an upcoming wedding. Now I’ve turned a lot of pens, but never a desk pen, which sits in a “funnel”, rather than being clipped into a pocket.

Desk pens differ from other pens in that the top section is longer, and has a blind hole—it doesn’t go through the top. Instead, there’s a finial there. That means I couldn’t mount the blanks on a pen mandrel as I’d normally do. I needed a mandrel that could grip the upper pen blank from the inside, and support it as I turned it. What I needed was a tiny pin chuck. Today.

Filing the rod to size

Fortunately, they’re easy to make. Since I was building the pens with 7mm components, I started with a nail and some 1/4″ tool steel (O1 or W1 steels are readily available at hardware stores). 1/4″ rod is just a few thousandths of an inch too big to slide inside 7mm barrels. So I cut off a length, mounted it in a collet chuck on my lathe, and filed it to size. Note that when you file on the lathe, you do it left-handed, so the end of the file is off to the right, away from the chuck. You can really get hurt doing it right-handed, if the end of the file catches in the chuck.

Five minutes later, the barrel slid on easily.

I know filing steel rod to size sounds tedious, but it took no more than five minutes to reduce it to the point where the brass barrels slide on smoothly. There’s not much steel to remove. I polished the rod with sandpapers up to #600, and  then I was ready to cut the flat.

A pin chuck projects into a hole just slightly larger than it is. The chuck’s rod has a flat on it, and sitting on that flat is a smaller rod, such as a nail with the head cut off.

The diagram at left is a view from the tailstock of a hollow tube such as a pen tube mounted on a pin chuck. When the lathe spins counterclockwise, the little rod trapped in the flat rolls to the right, jamming the tube onto the pin chuck. It works amazingly well, jamming into blind tenons and tubes with dependability and repeatability.

Next post, I’ll talk about finishing and using the pin chuck.