Shop Knife 4: Hafting

Published on May 30, 2011 in Tool making. Closed Tags: .

 

The blade, nicely polished

Well, my daughter’s wedding is over, so there should be a little more time for writing now.

The previous posts took you through turning an industrial bandsaw blade segment into the blade of a shop knife. Here you see it after the polishing steps.

Now for the final procedure—”hafting”, or attaching an handle.

We have to overcome a technical issue in hafting the blade. There are no holes in it to secure the blade to the handle, and the blade is hardened steel. You can’t drill through it with normal twist drills. Here are a couple alternatives. You can drill with a diamond drill, which is harder than the steel. Those are expensive. Or you can soften part of the blade and then drill through. I chose the latter approach.

 

The rivet hole area is spot annealed, then drilled through.

I had a 1/4″ solid carbide router bit, too dull to use. I chucked it in the drill press with the shaft side down, clamped the knife blank securely on an insulating surface, then brought the spinning rod down against the blank. In only a moment, the spot under the rod heated to several hundred degrees and the tempering colors began to radiate out, indicating that the spot had been softened. This process is called “spot annealing”. I let it air cool for a few minutes, then sharpened a 1/8″ drill bit and drilled easily through the annealed spot.

 

All the pieces, ready to assemble

I sawed a scrap of live oak firewood into two pieces to make the matching sides of the handle. I hand-planed the interior surfaces so they’d glue together without gaps, then used a straight bit in my router table to cut a pocket for the blade into one of the two handle sides. After that, I laid the blade in its final position in the pocket and drilled through the hole in the blade, making a hole in the handle side. I attached the two handle sides together with double-stick tape and drilled back through the same hole, now from the outside, to make a matching hole in the second handle side. Then I cut the outside of the handle blanks to shape while they were taped together. Finally, I cut a rivet from a length of 1/8″ brass rod. You see all the parts, ready to assemble, in the photo.

 

The finished shop knife

At last, it was time to put it all together. I glued the two sides of the handle together with yellow glue, then epoxied the blade and rivet into place. I then shaped the outside of the handle with rasps, files, and sandpaper until it felt comfortable and the rivet was perfectly flush with the surface on each side. Then I sharpened the blade.

The result is a knife that has served me well for general shop use. Since then, I’ve made a couple others from the same bandsaw stock, shaping the blades for various special purposes. I would up with free knives that exactly met my needs, and kept a little steel out of the landfill or recycling bin.

Shop knife 3: Polishing

Published on May 20, 2011 in Tool making. Closed Tags: , .

It’s been hard to find time to post recently. I just returned from a business trip, and my daughter’s getting married Sunday, so we’ve all been pretty busy. I’ll try to do better next week.

Start the finishing with sandpaper, just like with wood.

I finished the last post talking about shaping the blade. Now it’s time to make it pretty.

Think of polishing as extreme sanding. Each stage removes the scratches from the preceding stage. When the width of the scratches which remain is smaller than the wavelengths of visible light, the surface reflects like a mirror. It’s completely polished. Since I’d already wire-brushed the surface, I started with #P400 wet-or-dry paper and a little water lubricant, and sanded until I saw an even scratch pattern. Same with #P600.

Emery compound on a sisal wheel cuts fast

At this point I switched to buffing wheels and compounds, holding the blade in vise grips against the wheel. I use a Grizzly Knife Belt Sander for this work, mounting various 8″ wheels on the left arbor as needed. In this case, I started with a sisal wheel and black emery compound. (There’s an excellent set of instructions for polishing with wheels at Caswell Plating.) Sisal is a hard, naturally abrasive fiber that cuts fast in wheel form, and is a good applicator for coarse cutting compounds such as emery. It removes all the sanding scratches quickly, leaving a smooth surface. When applying these compounds, use just a little compound and use it often. Don’t apply so much you build up a residue of compound on the blade.

Next step is “white diamond” buffing compound on a spiral-sewn cotton wheel. The cotton wheel is softer than sisal, while the spiral sewing gives it considerable rigidity for fast cutting. It’s important to dedicate a buffing wheel to each compound. Don’t try to clean off coarse compound and then do fine polishing with the same wheel.

I finished up with green, chromium oxide polishing compound on a soft cotton buff. This yields the final, mirror-like surface. Next, fitting the handle.

Shop knife 2: shaping the blade

Published on May 11, 2011 in Tool making. Closed Tags: .

breaking the blade out of the stock

Previously, I showed how to score along the outline of the blade with an abrasive cut-off wheel, chewing away the metal to weaken it. Bandsaw blade stock is fairly brittle, so it will snap where you create a “stress concentrator” such as a deep scratch. Now, clamp the blank in a metalworking vise with the score line just above the jaws and tap it with a hammer. (Remember your safety glasses!) The waste should snap off cleanly. If it doesn’t, grab the waste in a pair of ViseGrips and bend it back and forth a little until it breaks looks. This is a lot faster than trying to grind the whole blade out of the blank.

Blade blank, ready for shaping.

Now take the blade to your grinder and smooth all the edges, bringing the outline to it’s final shape and removing all the burrs before one hooks into your hand.

Once I’ve ground the blank to final shape, I grip it in ViseGrips and use a rotary wire brush to develop an even scratch pattern across the whole surface, removing any blemishes.

Wire brushing the blank in preparation for polishing.

Wire wheels sometimes throw bristles, so it’s good to stand out of the line of fire. And be sure to present your blade to the receding side of the wheel, as in the photo at left. If you feed it into the top of the wheel, the wheel might grab the blade and throw it at you.

The next step is to polish the steel.(You need to get the surface looking the way you want it to before starting sharpening, since polishing later can take off the sharp edge.) There’s no magic to polishing. It’s very like sanding in that you start with an abrasive coarse enough to remove the worst scratches in the surface, then go finer and finer. But instead of stopping at #180 as you might with wood, you go all the way to chromium oxide (green) honing compound for a mirror finish.

Next: the polishing steps.

Making a shop knife

Published on May 7, 2011 in Tools. Closed Tags: , .

Shop-made knife

The question came up recently in a class, “how do you make a shop knife?”.

Now maybe you’re thinking “The real question is, WHY would I make a shop knife!”, but sometimes you can’t find what you need on a store shelf. Maybe you want a special size, shape, or handle. Shop knives are easy to make from scrap (read, “free”) materials, and you can make them just the way you want. This next series of posts shows how.

By the way, you’ve perhaps noticed that I haven’t posted in a while. I’m helping build a new company, and that’s taking most waking hours. I’ve hardly had time to get into the shop recently.

I make shop knives from pieces of worn out 1″ industrial bandsaw blade. Any metal supplier that cuts metal will throw these out regularly, and you can sometimes have a lifetime supply for the asking. For the knife in the picture, I began with about a 4″ piece.

Length of bandsaw blade with knife blade marked.

Now bandsaw blade stock is difficult to shear. It’s hard and somewhat brittle. But it’s easy to break into the right shape. I just put a length in a metal vise with the “cut” line right at the top of the jaws, then pull the piece over a bit and whack it right above the jaws with a hammer. (Remember your safety glasses!) It snaps cleanly at the jaw line.

Grinding away the metal before snapping it

In the photo above, I’ve cleaned the bandsaw blade stock and painted it with Dykem, a shellac-based machinist’s dye available from Amazon.  Then I scratched the outline of the blade I want to make. Next I put a little cutoff wheel into a die grinder (a big, strong rotary tool), and ran it along the scratched outline, abrading away most of the metal there.

Next, shaping the blade.

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.

If you like what you see, you can subscribe to regular emails announcing new articles.

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.

Comments on Grizzly’s 10″ Wet Grinder

Published on February 18, 2011 in Machines and Reviews. 2 Comments Tags: , .

Tormek's T-7 wet grinder

Maybe you’ve thought about a wet grinder to sharpen your tools. Having used one for over 15 years, I can tell you they’re a wonderful way to put edges on carbon steel chisels and plane blades. You just can’t burn the steel, no matter how ham-handed your grinding. That means you can grind to a feather edge—something you can’t do with a dry grinder without overheating the edge and drawing the temper. Once you see some heat coloring, it’s already too late!

Jet’s JSSG-10 10″ Wet Grinder

Cost is what keeps most people from using these grinders. Tormek, grandaddy of the category, sells their T-7 system for $600. Then there are the accessories… But competition is bringing prices down. Jet sells their version of the tool, the JSSG-10, for $320 (at Amazon, who also sells the Tormek). In a smart move, Jet made their machine accept all the Tormek accessories, so they had a full line of fixtures available before they got all their own on the market.

Grizzly’s T10010 10″ Wet Grinder

Now Grizzly has joined the party with the T10010, its version of the same tool. At less than $200, it’s a new low price point. But how good is it?

Woodworking friend and Sawdust Shop regular Julien Lecomte wrote me about his experiences with the Grizzly. With his permission, I’ve published his message:

“Since you teach the sharpening class at the Sawdust Shop, I thought I would report on my experience with the Grizzly wet grinder.

I use it solely to shape the primary bevel on my chisels and plane irons. I haven’t tried the leather strop yet.

One thing I noticed immediately after unpacking the unit was that the wheel was not true at all! I purchased the Tormek jig to true the wheel (almost all the Tormek jigs fit the Grizzly unit) and was back in business in no time.

Overall, I am very happy with this wet grinder. It misses a few nice features of the Tormek, such as the fine adjustment of the guide rod, but for only $180 (vs $400 for the Tormek), I warmly recommend it.