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This article was published in the Fall 2009 edition of  Woodturning Design.

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Shear Spear

Introduction

The pyramid point tool is a versatile tool that leaves a good surface off the tool because when held horizontally it automatically works as a shear scraper. But the point of the pyramid tool is rather blunt—usually in the neighborhood of 80°, which limits its usefulness in making adjacent beads or undercutting design elements. I’ve tried for years with limited success to modify the tool to give it a more acute point while still maintaining its shear scraping action. Even reducing the angle as little as 20° to around 60° entailed some really long and forever-to-grind bevels. Perhaps it’s a sign of limited patience, but I’ve found that the longer I have to grind the less likely the tool will be sharp in the end.

 

This year it finally dawned on me that I could start with rectangular stock instead of round, and I didn’t have to sharpen the tool along the whole 45° bevel. It not only worked but it was cheap. I bought a 1/8” x 1/2” HSS parting tool from Penn State Industries for $9.95, complete with handle, and cut the tip with an angle grinder to a rough 45°. I made a simple jig to simplify sharpening (it’s hard to precisely match the small bevels on the tip by eye) and ended up with a sweet little detail tool with an effective point of nearly 30°. It will form and even undercut beads on bowls, and cut beads that are too small to roll with a skew on spindle work. Not that I recommend it, but the truly skew terrified could substitute the Shear Spear for V-cuts, beads, facing cuts, and forming pommels.

Making

Prep

Start with a 1/8” x ½” parting tool as in Fig01. This must be a parting tool with straight sides, NOT a diamond cross section parting tool. You could start with some other source of hardened High Speed Steel such as an old jointer blade as long as you blunted the sharp edge, but compared to $9.95 complete with handle it would be a lot more work. Mark a 45° line as close to the tip as you can get with a full width as in Fig02. Clamp the tool securely and cut along the line with a cutting wheel mounted in an angle grinder as in Fig03.

Fig01

 Fig01        A 1/8" x 1/2" parting tool, which is the raw material for the Shear Spear.

Fig02

Fig02        After marking a 45° on the end of the parting tool.

Fig03

Fig03        The large bevel has been cut with a cut-off disc mounted on an angle grinder.

Jig

The 45° bevel of the tool is big and easy to match when adjusting the extension of your grinder V-block, whereas the critical small bevels are not. A simple jig solves this problem by eliminating re-adjustment of the V-Block setting when sharpening the small bevels. Start with a scrap piece of 2x4 construction lumber. Cut a square end and lay out a rectangle that is 1-1/2” wide and 1-3/8” long as in Fig04. Cut out the rectangle with the saw of your choice.  If you are using a 6” grinder or your overall tool length is radically different from my overall length of 11-3/8” you may need to adjust the jig length.

 Fig04

Fig04        After laying out the sharpening jig on a scrap piece of 2x4.

Clamp the block on your drill press with one a 1-1/2” square face up and drill a shallow recess for a round ceramic magnet with a Forstner bit as in Fig05. Glue the magnet in with CA glue. You could eliminate this step, but the magnet keeps the jig in place, plus you can stick the jig on the side of your grinder to keep it from getting lost if you’ve got a shop that looks like mine. Test fit the jig to make sure it fits all the way down into the pocket of your sliding V-block. You may need to cut off the bottom corner. My One-Way Wolverine system has a deep enough pocket to securely register the end of the handle with the jig in place. If your system has a shallower V-block you can wrap sheet metal, such as aluminum flashing around the bottom two faces of the jig to create a V for the handle to rest in—look ahead to Fig17. The completed jig is shown in Fig06.

Fig05

Fig05        Using the drill press to make a recess for a round ceramic magnet which will keep the jig in place both in use and in storage.

Fig06

Fig06        The completed sharpening jig.

Sharpening

The first step in shaping and sharpening the tool is to clean up the bevel surface left by the angle grinder. Without using the jig, place the butt of the handle in the grinder’s V-block and adjust the extension so that the middle of the bevel contacts the grinding wheel as in Fig07. Turn on the grinder and grind until the entire bevel looks clean and the bottom edge is sharp.

 Fig07

Fig07        The set-up to grind and sharpen the large bevel.

Fig08

Fig08        After grinding the large bevel.  As the tool is High Speed Steel, which keeps its temper except under extreme heating, the discoloration from heat of grinding is of no concern.

Place the jig in the pocket of the V-block with the magnet to the rear. Do NOT change the extension of the V-block, as that’s the whole point of the jig. Place the handle in the somewhat truncated pocket of the V-block with the point of the tool to the right and the heel of the tool rotated away from the grinding wheel slightly (about 15 °) as in Fig09. Grind gently until the about half of the toe edge is removed—do NOT try to sharpen the whole long bevel. Now flip the tool over so that the toe is on the left. Angling the heel away the same angle as before as in Fig10, gently grind until the small bevels meet at a point slightly above the bottom edge of the tool—this will ensure the point is sharp.

 Fig09

Fig09        The set-up to grind and sharpen the small bevel on the left side of the point.  The V-block extension is unchanged, but the jig has changed the angle of the tool relative to the grinder.

Fig10        The set-up to grind and sharpen the small bevel on the right side of the point.

Take a good look at your work now. Make sure the small bevels are of equal length, and that the point is as acute as you want it to be. The tool is now ready to use. To resharpen the tool (and shear scrapers work best when kept really sharp), always adjust the extension of the V-block so that the grinding wheel matches the angle of the long bevel. Sharpen that bevel, then add the jig without disturbing the V-block extension and sharpen the small bevels. Fig11 thru Fig15 show the completed Shear Spear.

Fig11

Fig11        After sharpening the Shear Spear.

Fig12

Fig12        A close up view of the Shear Spear from the side.

Fig13

Fig13        A close up view of the Shear Spear from the bottom.

Fig14

Fig14        A close up view of the Shear Spear from the top.

Fig15

Fig15        The Shear Spear from the top, side, and bottom.

Alternatives

Beading Tool Jig

If you made the jig to sharpen a beading tool in my last Woodturning Design article, you can use it to sharpen the Shear Spear. You make the grooves in the same fashion (see WTD #22 or my web site: www.DavidReedSmith.com). File one groove on the handle aligned with the heel of the bevel 4-1/2” from the tip. File the other two grooves 105 ° apart from the first groove 5-7/8” from the tip. Fig16 shows a Shear Spear prepared for sharpening with the beading tool jig.

Fig16

Fig16        A Shear Spear with the handle modified to enable sharpening with the beading tool jig.  If the filed recesses were ½” instead of 3/8”, it would work with a Tormek.

Tormek

If you sharpen with a Tormek (or clone) you can sharpen the Shear Spear in the same fashion as the beading tool following the directions in WTD #22 (or my web site). Make three semi-circular grooves with a ½” file across the handle at 90 ° to the handle’s long axis. Center the first groove aligned with the heel of the large bevel 4-1/2” from the tip of the tool. The other two grooves are 105 ° apart from the first groove and 5-7/8” from the tip of the tool. Set the extension of the tool rest by matching the bevel to the grinding wheel when the first groove is resting on tool rest. Sharpen that bevel, then, without moving the tool rest, use the other two grooves in turn on the tool rest to sharpen the two smaller bevels.

Bigger

If you feel that the Shear Spear is too light weight, you can start with heavier stock. But please remember this is designed to be a detail tool, not a roughing tool. Penn State Industries has a ½” round nose scraper that is ¼” thick for $12.50. Make the tool in the same fashion. As the tool handle is longer, the jig needs to 1-7/8” long. This doesn’t leave enough room to securely cup the tool handle in the V-block. I solved this problem by wrapping sheet metal around the bottom two surfaces of the jig to create an extended cup as in Fig17. You could also just cut the handle so that the over-all tool length is the same as the 1/8” version:  11-1/2”. Fig18 shows the tips of the 1/8” and ¼” versions of the Shear Spear.

Fig17

Fig17        A jig modified to sharpen the longer handled ¼” Shear Spear.

Fig18

Fig18        Shear Spears made from 1/8” x ½” parting tool and ¼” x ½” scraper.

Using

Faceplate Orientation

I have found the Shear Spear to be very user friendly in faceplate orientation. Just hold the tool horizontally with the toe down. Push the tool where you want it to go. The tool will automatically cut using a shear scrape. The tool is stable enough in use that if you have vibration problems you can hold the tool in one hand and steady the bowl with the other hand. To start a V-groove just plunge the tool in as in Fig19. To deepen the groove you can cut from alternate sides.

 Fig19

Fig19        Making a V-cut in a faceplate oriented pine “bowl” with the point of the Shear Spear.

To round over an element, such as when making a bead, use one of the small bevels. The tool should still be held with the handle horizontal and the edge leading to the toe flat on the tool rest. You may find it easier to turn successively smaller facets rather than swing the tool through an arc. When you are swinging the tool watching the small bevel it’s rather easy to loose track of the point and put it somewhere you don’t want to be. Fig20 shows cutting a chamfer to begin rounding over a bead.

 Fig20

Fig20        Rounding over a bead on the pine “bowl” with the small bevel of the Shear Spear.

The detail control and shear scraped surface requiring minimal sanding should give you a wide range of design opportunities. Fig21 shows an undercut bead made with the Shear Spear. This was an un-hollowed pine “bowl” cut in half to demonstrate how far the bead was undercut. Fig22 shows a significantly undercut rim treatment. Again, this is a construction pine bowl cut in half.

Fig21

Fig21        An undercut bead on a pine “bowl”.  The bowl has been cut in half to clearly show the amount of undercut.

Fig22

Fig22        An undercut bowl rim made with the Shear Spear.  The bowl again has been cut in half.

Spindle Orientation

Using the Shear Spear in spindle work is much the same as bowl work, except perhaps for the shavings produced. The tool is held with the handle horizontal. The edge that leads to the toe is kept flat on the tool rest. To start a V-cut just push the tool straight in towards the center of the spindle as in Fig23. You can deepen the cut by cutting from alternate sides. It is NOT as efficient as a properly wielded skew, but you should be almost as happy with the surface left from the tool.

 Fig23

Fig23        Making a V-cut in a pear spindle.  Small V-cuts can be made by simply pushing the tool straight in.  Large V-cuts will require multiple cuts on alternate sides.

Making a facing cut on the end of a spindle, as in Fig24, is like making a V-cut with most of one side missing.  There will be some tendency of the increased resistance on the wood side of the tool to veer it in, so be aware and concentrate on keeping the cut on course. 

 Fig24

Fig24        Using the Shear Spear to face the end grain of a pear spindle.

The Shear Spear can be used to cut beads. With beads over ¼” in size it would be more efficient to use a skew, but on very small beads where rolling the skew that tightly is difficult, the Shear Spear can be put to good use. Begin by marking the extents of the bead. Use the point to make a V-cut to define each side of the bead. Then use the small bevels to make successively smaller facets on both sides of the bead. You may find it less awkward to change to a left-handed grip when cutting on the right side of the bead and it will be good practice anyway.  Light sanding will finish rounding over the bead. Fig25 shows these steps in progression from left to right.

 Fig25

Fig25        The succession of cuts for making beads with the Shear Spear.  From left to right:  marking; V-cuts; chamfer on left; chamfer on right; facets between chamfers; finer facets; final light sanding to shape.

Cutting a pommel is much like making a V-cut, only starting with square stock. Fig26 shows a series of pommel cuts. The one in the middle is with a skew—and it had the least clean bottom. It felt no less efficient doing the pommel cuts with the Shear Spear instead of a skew, and it felt quite controlled. Even the rather untraditional undercut example on the right didn’t lead to a white knuckle grip.

Fig26

Fig26        A sampling of un-sanded pommel cuts in maple.  Even when making the bizarre undercut example on the right the tool felt safe and controlled in use.  The middle pommel cut was made with a skew for comparison and the surface quality is undistinguishable.

 

Materials

1/8” x ½” parting tool to modify

Scrap 2x4 construction lumber for sharpening jig

Round ceramic magnet (1/4” to ½”)

Tools

Protractor for marking 45° angle

Angle grinder with cut-off disc

Bench grinder with sliding V-block or other sharpening system

Drill press with Forstner bit to match magnet

Author

David Reed Smith is a basement turner, tinker, and I guess by now writer, living in Hampstead, Maryland. He welcomes comments, questions, and suggestions by email at David@DavidReedSmith.com. A web version of this article with a few more pictures is available on his web site at www.DavidReedSmith.com.