Learning to make your own tools is a step up for the serious woodworking carpenter
Most of my work is at the high-end of the New England custom home market. For the jobs I do, in Boston brownstones that even today sell for several million dollars, there are no off-the-shelf parts—everything is completely custom, or an exact reproduction of work done in the 18th or 19th centuries.
Early in my career, I learned how to grind the shaper knives for my big old Yates-American cast iron shaper, and I’m glad I did. That skill has saved me from having to order custom knives for almost every job I do. There are many good companies that will supply custom cutters from a sample or a CAD drawing, but by grinding my own I can save a little money, and make the moldings the day I decide I need them. I can also modify the cutters if the molding doesn’t look quite the way I want. Not only that, but in our shop we take great pleasure and pride in being able to build architectural millwork and furniture from scratch. Sometimes we have to, or want to, use 19th-century techniques to get results that are as good as the old carpenters’ we learned from—they’ve been dead for 100 years, but we get to look at their work every week.
We are all carpenters because making things is in our hearts more than making money, and I’m not going to buy something if I can make it as well, or better, myself. Learning to make your own tools is a step up for the serious woodworking carpenter.
In the time it takes Mike Kennedy, who works with me in my shop, to rip, join, and plane the railing stock (see photo, left), I can cut and grind the shaper knives. I think we’ve made over 40 different handrails over the years. And I’ve got a couple of sets to make next week.
Before I get into the actual process of knife cutter grinding, I want to say a few words about design.
Moldings aren’t just random squiggly lines cut into wood. Both the shapes and proportions of moldings have a long history. Moldings are meant not just to connect different levels with graceful curves, but also to create interesting lines of light and shadow. We don’t have to reinvent the wheel every time we design a molding or handrail. Almost every traditional and modern molding has its origin in the Classical Architecture of the ancient Greeks and Romans more than 2000 years ago, or in the Cathedrals, castles and manor houses of the Middle Ages—the Gothic period. 18th and 19th century builders studied this stuff, and you can, too. There are many inexpensive reprints of books about classical architecture with actual molding patterns in them, as well as reproductions of old millwork catalogues. (* See end of article for a selection of book recommendations.)
Of course, looking at the exteriors of traditional buildings is free, and the details can be scaled down for residential interiors. Churches and temples often have beautiful woodwork. Helen, my wife, and I are at that age when a lot of our friends’ kids are getting married; we went to three weddings this fall. I wonder if she’d notice if I brought my sketchbook to the next one.
Handrail also has to meet strict requirements of building codes. To see a good explanation of the required profiles, download this great IRC Stair Code Visual Interpretation from the Stairway Manufacturers Association.
I cut the steel stock for the knives from a bar of shaper steel with a 10-in. x 1/8-in. fiber-reinforced cut-off wheel mounted in an antique no-tilt no-slide Makita chopsaw.
Shaper steel is available in many sizes and types. I have both lock-edge and corrugated-back heads for my shaper. I also grind knives for my Williams and Hussey machine, which uses special bar with bolt hoses drilled on 1-in. centers.
I buy my shaper steel over the phone from Charles Schmidt Co. in Montvale NJ. I almost always use 1/4”-in. thick XLW-type steel in 25-in. bars of various widths. I always make two identical knives for each molding—they go together in the shaper head, and balance each other. I try to make them as close to identical as possible, so that they each cut the same amount.
I start with a full-size paper printout from a CAD or freehand drawing of the railing or molding profile.
|I glue the paper drawing to a piece of 1/8-in. acrylic or plastic laminate, like Plexiglas or Formica,|
|then cut out the shape of the railing profile using a scroll saw with a fine blade.|
If I am copying an original molding, I cut the sample off at a 15-degree angle (about the angle that the cutter will hit the wood) and trace that section onto the plastic. I spray the knife blanks with black stove paint, and, using the plastic template and a needle-sharp awl, I score the profile on the face of each knife.
Remember that the shape of the knife is the negative of the shape of the finished railing. It’s a good idea to mark the knife on the side that will do the cutting, and to mark the side that you want up when the knife is in the machine. Don’t ask me how I learned these last few tips.
Now comes the dirty part.
Grinding knives by hand is dangerous business
This technique isn’t for everyone. It’s dangerous—like a lot of the things a carpenter or woodworker does. If my hand slips while I’m grinding, I can get a nasty abrasion from the wheel, and the knives are very sharp—they can cut you even without being in the shaper and running. Grinding wheels can shatter, and the pieces can cause serious injury. The dust from grinding is dangerous to breathe, and steel filings, sparks and silica from the wheel are eye hazards. It can be a fire hazard, too: the steel can become hot enough to burn.
I use a dust mask and eye protection. I also work looking through an illuminated magnifier with a plastic lens, which gives an additional layer of eye protection, as well as improving my accuracy. I use a spray mister which cools the work, keeps the grinding wheel sharp longer, and helps to control dust. I set the tool rest very close to the wheel so the work or my finger can’t slip between.
I hold the steel with a very firm grip. I mount and check the grinding wheel according to the manufacturers instructions. Before I put the wheels on the machine, I hold them with my finger through the center hole and tap them with the plastic end of a screw driver—they should ring like a bell, not make a dull thud, which indicates cracks. Good lighting is very important, as well as a comfortable posture—I usually grind sitting on a stool with both feet on the floor.
Most important, I always pay very close attention to what I’m doing. I don’t recommend this technique for everyone. But I’ve never had an accident at the grinder, except for an occasional scraped knuckle, and I’ve ground hundreds of shaper knives. Whenever I’m working with power tools or hand tools, whether I’m sharpening, sawing, turning, carving, or cutting miters on the chopsaw, I try to stay focused on the task. I know that any machine that will cut wood or steel can also cut me. There is no smart way to hurt yourself woodworking, but there are a million stupid ways. (THISisSafety)
A note on my equipment:
I use a 10-in. diameter pedestal-mounted grinder that is bolted to the floor. Mine is Dayton Brand, which I bought new from Grainger’s 20+ years ago. I believe they still carry it.
Attached to the grinder is a mister/cooler, from MSC, powered by my compressor. You can get one for about $140.
Both of these companies also carry illuminated magnifiers.
I start grinding with a 1/8-in. fiber-reinforced 10-in. cut-off wheel to rough out the knives. I set the tool rest level at the height of the center of the wheel so it makes a square cut. I turn the grinder on, start the mister, and dress the edge of the wheel with my diamond dresser to clean and center the wheel. Then, with a series of cuts from different angles, I remove as much of the excess steel as possible.
[Note: For a look at Jed's grinding technique, see the video at the end of this article.]
Next, I use a 1/4-in. x 10-in. 36-grit aluminum oxide wheel to rough out the molding profiles. The wheels I use are Norton brand and come from Charles Schmidt Company, the same place I usually buy shaper steel. They are very friable, that is: crumbly, which is a good thing, because it makes them fast-cutting, and they don’t clog up with metal from the knives.
First, I reset the tool rest to 45 degrees. The angle doesn’t have to be as acute as a plane blade (30 degrees); it just has to be steep enough so the heel of the bevel doesn’t hit the wood when it’s in the shaper.
|The first pass I make is to bevel the knife; I’m just removing stock from the underside of the knife blank. Then I start grinding away at the profile.|
With the square wheel, I cut up to the line on the straight parts of the knife, and on any convex shapes.
Finally, I put a very slight bevel on the square wheel, making sure that the corner is sharp—not rounded—and dress the inside corners of the knife (which will be the outside corners of the molding) nice and sharp.
|Often, I’ll clean up the knife, turn off the spray for better visibility, and make one last, very light pass with both wheels for accuracy. This is sparking-off—a cut so fine that it just barely makes a spark.|
|Before leaving the grinder, I weigh the knives. They must be balanced, or the cutter head will vibrate. They should be within 1/10 of gram. It shouldn’t be too hard to figure out where to remove the stock from the heavier knife.|
Finally, I hone the knives razor-sharp with a hand-held stone. Gesswein is a good company for stones and stone oil.
|I make a test cut,|
|then check the profile against the drawing.|
We make both straight, large, and tight radius level-turn rails with these knives—completely custom. A shaper is one of the most versatile tools in a woodworking shop, and also one of the most dangerous. So, know what you’re doing, and pay attention.
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Please don’t try anything you see in THISisCarpentry, or anywhere else for that matter, unless you’re completely certain that you can do it safely.
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Asher Benjamin, The American Builders Companion — an influential book written for Federal era (c. 1810) builders
Edward Whitehead and Frank Chouteau Brown, Early Homes of Massachusetts and other reprinted titles of the White Pine Series — contains beautiful detail drawings of Colonial-era millwork, exterior and interior
William Ware, The American Vignola — a good collection of classical revival designs
C. Howard Walker, Theory of Mouldings — just what it says, originally published 1926
Roberts’ Illustrated Millwork Catalogue — and several other reprinted millwork catalogues from the late 1800s…Victorian!