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Thread: Skew grind Angle - newbie Here!

  1. #1

    Skew grind Angle - newbie Here!

    I bought a 1" skew chisel from someone In another forum. It is 5/16" thick. My understanding is the ground surface length should be 1 1/2 times the thickness. When I laid this out the angle comes to about 25 degrees. Does this sound correct?
    Thanks!

  2. #2
    It does not sound right to me. I suggest that each side should be ground at 18 - 20 deg, resulting in a 36 - 40 deg edge.
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  3. #3
    I should clarify that the 25 degree angle is on one side only. So it would be 50 degrees combined.

  4. #4
    Tom, you may want to review this thread - https://www.sawmillcreek.org/showthr...Angle-Of-Skews

    Left click my name for homepage link.

  5. #5
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    Also there are several videos on youtube showing presentations by Stuart Batty to woodturning clubs that feature grinding angles. He favors a 40 degree angle on gouges so for a skew that's 20 degrees on each side (give or take.) Videos are worth watching for other info as well.

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    Quote Originally Posted by Tom Norton View Post
    I bought a 1" skew chisel from someone In another forum. It is 5/16" thick. My understanding is the ground surface length should be 1 1/2 times the thickness. When I laid this out the angle comes to about 25 degrees. Does this sound correct?
    Thanks!
    No, your math is wrong. The calculated angle per that guideline is 19.5 each side or 39 total.
    Beranek's Law:

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    L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.

  7. #7
    Brian Havens does a good job explaining the affect of different grind angles on a skew.

    http://www.youtube.com/watch?v=yhuEVVSkDtE

  8. #8
    Correct angle seems to be a many varied and complicated thing. Some videos I have watched very the angle depending on the wood. then there is the angle across the shew as well. Stuart Batty and Alan Lacer are the two I would heed. Lacer gave a demonstration to the Dallas woodturners, available on youtube, that is over an hour and only covers some of the skew uses. there are a few good German youtube videos as well and one or two have really good diagrams of skew angles and methods.

  9. #9
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    Hmm...seems somewhat more complex than I imagined. I'm new to woodturning and have done mostly bowls but would like to learn how to use a skew (just for small stuff for now). What are the recommendations for an all-purpose skew (thickness, angle, grind angle, etc) and would you recommend starting with a cheaper tool or starting with a Thompson?
    Last edited by Thomas Wilson80; 01-08-2018 at 10:21 PM.

  10. #10
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    skews, grinds and learning

    Quote Originally Posted by Thomas Wilson80 View Post
    Hmm...seems somewhat more complex than I imagined. I'm new to woodturning and have done mostly bowls but would like to learn how to use a skew (just for small stuff for now). What are the recommendations for an all-purpose skew (thickness, angle, grind angle, etc) and would you recommend starting with a cheaper tool or starting with a Thompson?
    Thomas,

    It can be complex, but simple too - the skew is the most basic tool, the straight edge much simpler than the compound curves on a spindle or bowl gouge.

    If you have mostly turned bowls, I strongly encourage your interest in learning the skew and spindle turning. I am a firm believer in what is echoed by some of the best all-around wood turners I know of: spindle turning will teach you the fine tool control that will let you turn anything, including bowls. I've heard this in person from some (Frank Penta, Jimmy Clewes, Richard Raffan) and in books by Keith Rowley, Mike Darlow, and others. This doesn't work the same in reverse. Some of the best bowl turners I know can't use a skew and some can barely turn a spindle.

    When I started turning everyone told me to keep away from the evil skew. I heard lots of comments about using them as scrapers and for opening paint cans. (Most of this was from bowl turners.) But when I read the books I found out the experts were using skews so I thought if they could do it so could I. I taught myself from several books, primarily Raffan's "Turning wood" and Darlow's "Fundamentals of Woodturning."

    For small things, a smaller skew is fine. I have skews from 1/4" to 1-1/4". My favorite skews for smaller work (for example, thin spindles) are 1/2". For details such as small beads and small v-grooves I usually reach for a 1/4" round skew but it's not too good for shaping tapers and things unless they are very small. For larger diameters and for roughing I often use a 1" or 1-1/4". A 3/4" is a good compromise. The larger the skew, generally the thicker is better. A smaller skew is easier to sharpen than a larger one.

    Some of the basic cut with a skew are planing, peeling, beads, shallow coves, v-grooves, and facing. Planing is done on side grain to make a smooth cylinder or taper. Peeling will very quickly reduce the diameter at one place, similar to using a parting tool correctly. Beads are often done with the "short point", the obtuse angled point furthest from the end (can be tricky!) The larger the skew, the more difficult it is to make coves. V-grooves and facing are about the same, cutting across end grain, usually done with the sharp point on the end (the long point). Facing is simply on the end, often making a flat face, slightly coned, or rounded. I find planing and cutting v-groove cuts the most useful - done right the wood surface can be almost glossy smooth needing little or no sanding. Planing and v-grooves are what I teach first.

    As for angles, there is the skew angle (the angle across the end looking from the flat side) and the included angle (looking down the sharpened edge from the edge of the tool).

    The skew angle is somewhat a matter of preference - it changes how you hold the tool on the rest. I haven't measured my angles so at the moment I can't say what I use, maybe 60-65-degrees (where 90-deg is strait across) I could measure some tomorrow afternoon. Some people prefer a curved edge - for example Richard Raffan grinds skews that are almost 90-deg at the tip (the long point) and curve to a sharper angle at the other side. This is a good compromise since it lets you do peeling cuts near the long point and have a more reasonable angle for planing cuts the further you get from the long point. (Curving the edge has certain other advantages too.) One thing, the smaller the skew angle (the "pointer" the end), the longer the grind on the cutting edge which can make a large skew more difficult to grind.

    The grind angleThere are several good reasons to use different grind angles, sometimes called the included angle since you include the angles on both side of the centerline between the two bevels. (If you set the tool rest at 20 degrees each half will be 20-deg so the included angle will be 40-deg.) It turns out that 40-deg is a pretty good angle for most skew use.

    There are several good reasons to use different grind angles. Some of mine are somewhat smaller angles and some are larger. One advantage to a smaller (sharper) angle is it will cut better; a disadvantage is it can be "grabbier" if you get careless. A larger angle does not cut as well or as cleanly but it is more forgiving. I sometimes give a larger angle skew to a beginner. Another lesser disadvantage of a smaller angle is on certain woods it can pull out long fibers on planing cuts. I also prefer a smaller included angle when cutting deep v-grooves.

    A cheaper tool is nice to start with since you can grind a lot of it away experimenting with angles. In fact, two cheap skews might be helpful so you can quickly compare one to the other. The better quality steel in the Thompson and other good tools is better in the long run since it will hold the edge longer. Also, I like the way Doug rounds one edge of the steel which makes it slide easier on the rest. If the steel has sharp corners they can dig into the rest - in this case use a stone or diamond hones and put at least some radius on the edges.

    A skew is easy to sharpen and probably better to sharpen without a jig, just a platform. Set the platform angle for the desired bevel and hold the tool flat on the platform so the cutting edge is exactly horizontal. Move the edge smoothy across the grinding wheel on one side until you have a cleanly ground bevel, then turn it over and grind the other side. It is best to make each bevel the same length so the cutting edge will be in the center of the tool instead of to one side. You can look at the bevels from the edge of the tool and see if they look about the same. I like to use a 600 grit CBN wheel.

    Learning the skew can be the tricky thing but it can also be extremely easy. I learned from books but a teacher would be better. I have been successful with a method I always use to teach beginners. In fact, the skew is the very first tool I put in the hands of someone who has never touched a lathe. After just a few minutes the beginner is making planing cuts on a cylinder and then a taper. The method I use to teach:
    - I always start with a blank already rounded to a smooth cylinder. Roughing a square blank can be noisy, shaky, and terrifying to a beginner.
    - Start with the lathe off
    - Show how to stand and hold the skew, supported against the body.
    - Make sure the tool rest is at the best height for the person. (I've had some short girls learning lately!)
    - Make sure the tool is in contact with the rest, the edge 45-deg to axis of the spindle, and the heel of the bevel in contact with the wood.
    - While I rotate the lathe slowly by hand, they adjust the tool so the edge starts cutting.
    - Explain that the cut should be on the lower half of the edge to keep the point away from the wood. (I mark the top 1/2 with a red sharpie)
    - Continue to turn the lathe by hand and let them play with the position to get a good cut.
    - Explain how to change where the wood is cutting on the edge. (twist the tool slightly)
    - Explain how to make a deeper or shallower cut (basically raise or lower the handle)
    - Show how to move the tool down the work to plane - for right-handed people we start cutting on the right and move towards the left.
    - Show how to move the tool with the body instead of the arms.
    - I continue to turn the lathe slowly by hand while they practice making cuts. They very quickly get the "feel" of the skew without the fear.
    - As the surface gets "lumpy" (it will at first!) I turn the lathe on and make it into a smooth cylinder again
    - Finally, I turn the lathe on the lowest speed (a good variable speed lathe is great here) and let them practice peeling cuts.
    - Turn the speed up and practice a few more seconds. Repeat.
    In just a few minutes of practice even a brand new student is comfortably making planing cuts with the skew at high speed. Maybe 10-15 minutes, 30 minutes max for an uncoordinated klutz. I have never had a student fail to learn to use the skew in the first lesson. I have also never had one get a catch with this method.

    As for the rest of the first spindle lesson, we next go to the spindle gouge and make coves and beads, to the roughing gouge to round a square blank and to for general shaping, then work on v-grooves with the skew. (V-grooves are harder than planing.)

    I posted this in another thread recently, but here is an example. This girl came for one spindle lesson and one face turning (bowl) lesson. Then over two years later with no other lathe access she wanted to make a "magic" wand for a Christmas present. (Yikes - a challenging project!) With a bit of review and practice and then a lesson on special techniques needed for thin spindles she turned this on her THIRD experience at the lathe. I was impressed. After completing it she said for her the easiest of the four tools (skew, spindle gouge, roughing gouge, parting tool) was the skew!

    Naomi_wand.jpg

    This is from yellow poplar.

    Oops, I got a little carried away and don't have time right now to see if all this makes sense and is relatively free from typos. Maybe it will help some.

    Best to find an experience turner for a lesson or two. Or hop in the car for a road trip and come visit - we can have an afternoon of spindle-turning and sharpening lessons and you can try out various skews and grinds! The cost is some good company and a maybe a good story or two.

    JKJ

  11. #11
    JKJ thanks for sharing such a comprehensive reply!! I am going to print bthis out and take it out to my shop!

  12. #12
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    I suggest trying different angles to find out what works well for you. Because a skew is not held in a fixed position you get to determine the angle of attack between the blade and the wood by how you hold it, so the "correct" angle for the grind will be the one you find most comfortable to use, and it will differ from turner to turner and situation to situation, as described in the great summary above. If it too obtuse you'll have to hold the handle in a funny position to present the edge, if it is too acute you might find the edge to be fragile and grabby. I have several skews, sharpened at different angles. I've never measured them so I can't tell you what the angles are.

    I sharpen my most used skew with a slight hollow grind, and a slight radius, per Richard Raffan. I hone the edge with a slipstone while turning so I don't have to keep going back to the grinder to keep a sharp edge. It just takes a few swipes every few minuted to maintain a very sharp edge.

  13. #13
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    Thanks so much John. Great info and very understandable. Now I just need to get a skew and find the time to practice.
    I would love to swing by your shop, but it's a little far from Chicago (though I do have family Greeneville, TN so maybe some day....).
    Tom

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    Quote Originally Posted by John K Jordan View Post
    I heard lots of comments about using them as scrapers and for opening paint cans.
    I laughed out loud on that one.
    I taught myself from several books, primarily Raffan's "Turning wood"
    Same here, and spent a long time making interesting spiral grooves on pieces while I learned. I eventually got the the point where I was able to get a finish on a curve that need little to no sanding, and would use that to make beads of all sizes (several different skews). Well worth learning.

  15. #15
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    Quote Originally Posted by roger wiegand View Post
    I hone the edge with a slipstone while turning so I don't have to keep going back to the grinder to keep a sharp edge. It just takes a few swipes every few minuted to maintain a very sharp edge.
    Thanks for the reply. What type/grit of slipstone do you use?
    Tom

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