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Skew Chisel Tear Out

Joined
Aug 7, 2012
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Location
Alabama
I am a newby and bought a used Vega lathe with a lot of accessories including Sorby turning tools that included several different skew styles. I have them sharp enough to shave hair so no problem there. I am finally able to run each of the skews across the turning stock without a catch but I keep getting some tear out. I have tried various angles from 1/2 degree from vertical to the much suggested 45 degree angle. I am practicing with Maple, Black Cherry, Brazilian Cherry and today I had better results with some old Dogwood so I am wondering if it it me or the wood? While running the skew across the wood it feels like the wood has a flat spot but when I stop the lathe to check it out I see the tear out. (The wood was smooth and without any damage before I tried the skew.) Tear out happens when I am cutting "down hill" as well as cutting parallel. The "tear out" is not like a splintered gouge tear out or a scraped tear out from a scraper. It is the small surface rips type tear out. Small areas that run along the grain. Other than these tear outs the rest of the surface looks like it has been sanded with 800.

Also, sometimes when using the skew the cut wood will "roll up" instead of flying off. I believe I am doing something wrong when this "roll up" happens?

Please advise and thanks inadvance for your time, effort and knowledge.
 
There are a lot of factors that can cause those problems. I haven't totally figured out all of them.
The rough bounce where the wood feels it has a flat spot is 2 things. ONe is too much pressure on the bevel. Lighten up and take a lighter cut if necessary. The other is simply the wood. Winter wood is harder than summer wood on some woods and it can create a bounce especially if you push to hard on the bevel.
I get the kind of tearout you mention occasionally. I can usually get around it by changing the angle the cutting edge is going across the wood and using lighter forward pressure. You can usually do this by either increasing the speed of the lathe, not pushing the tool forward as fast of both. Now here's the part I don't understand. I can take a small spindle gouge or detail gouge with a fairly small rounded tip and clean up these areas perfectly every time.
My detail gouge and skew are both sharpened to the same 35 degree included angle. So the difference is in the rounded tip. I think this helps because it's taking a smaller bite. The skew because of the realatively flat cut peels off a slightly wider shaving. At least that's what I think. I may be wrong I just know it works. When using a skew to plane the wood on Black palm I have had it do this really bad. It happens where the grain is roughly parallel to the cut. I can pull out the detail gouge and clean it up every time.
Hopefully someone else will have some solutions. Like you, my skews are very sharp and I use them a lot so I'm pretty comfortable with cutting angles and feed rates.
I have also had the problem of peel out using birds eye maple. Just in one or two spots a long a spindle. Again the detail gouge will save me when this happens.
 
Also, sometimes when using the skew the cut wood will "roll up" instead of flying off. I believe I am doing something wrong when this "roll up" happens?
This generally happens when you bring the short point into the cut instead of using the centre bit.

Tear out can be caused as John says by seasonal growth. Too short on the bevel can sometimes cause this as well.

Some of our Aussie hardwoods just will not cut cleanly with a skew or gouge so you use the skew as a scraper.
 
T
I get the kind of tearout you mention occasionally. I can usually get around it by changing the angle the cutting edge is going across the wood and using lighter forward pressure. You can usually do this by either increasing the speed of the lathe, not pushing the tool forward as fast of both. Now here's the part I don't understand. I can take a small spindle gouge or detail gouge with a fairly small rounded tip and clean up these areas perfectly every time.

A couple of thinking points. If you are cutting into climbing grain, even when going down hill, you'll get peck out. Way to verify is to look at the opposite side of the turning and see if you've got that super slick slice where you're going down grain and down hill. The answer in flat work is also the answer here. Increase the pitch angle to a scrape or decrease it to a slice that doesn't pick up the shaving so fast that it wedges inward and pecks out. Paradox there, because the high angle breaks the chips into near dust, the low makes a continuous gossamer shaving.

The gouge works because it's cutting, rolling and lifting in two directions, not just the one. You could also take a forged gouge - the traditional tool, and do the same on a broader shaving.

I'm not much for the skew, having de-evolved to the straight chisel, where I can keep the handle high and still get a good skew angled cut. I also have a single bevel chisel with a bevel to thickness ratio of > 3:1. You definitely don't want a high clearance angle with it, because it'll dive.
 
Straight grained Maple and cherry are not generally prone to tear out.
Curly maple and highly figured cherry can be problematic as the grain twists and skew can get under the grain sort of splitting action rather cutting. When this happens the tool pulls a chunk of wood up and it tears out.


If the blanks are cut off axis one side will tear and the other cut cleanly when you cut left to right.
When you cut right to left you get the same results but on opposite sides.

Check the face of your blanks. If you see lots of arrows from the grain it is off axis.
If you see lots of straight lines it is ok.

A couple of arrows in 6 inches is okay.


Al
 
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Check the face of your blanks. If you see lots of arrows from the grain it is off axis.
If you see lots of straight lines it is ok.

A couple of arrows in 6 inches is okay.
l

For the sake of common woodworking language, "arrows" translate to the more common expression "cathedral" grain. Good pictures here to explain. http://woodworking.com/ww/Article/Harvesting_Cathedral_Grain_7477.aspx Note the severely rising grain in the bottom board. Plane or turn from R to L and it's peck and rip. L to R is slick and happy. Short grain situation is something you really want to avoid on skinny stuff like finials, but might survive and look pretty with a pen.

If you're Ol' Roy with your froe and maul, pretty much anything you get is straight.
 
I've had it happen with Purple Heart and Black Palm and Willow. The grain was running parallel to the bed. No cathedral grain or arrows. Sometimes sharpening the skew helps. Sometimes using a skew with a flatter sharpening angle works. I try changing the cutting angle as well as changing skews and still occasionally have problems.
I will usually go to my detail gouge when this happens because I've also had it happen with my wide flat spindle gouges. I'm guessing the area you are cutting with is about the same as the skew on these wider flatter gouges.
Of course the downside of switching to the smaller detail gouge is trying to keep that surface perfectly flat which is why I use the skew in the first place.
 
I will usually go to my detail gouge when this happens because I've also had it happen with my wide flat spindle gouges. I'm guessing the area you are cutting with is about the same as the skew on these wider flatter gouges.
Of course the downside of switching to the smaller detail gouge is trying to keep that surface perfectly flat which is why I use the skew in the first place.

No, a curved line (edge) between two points is longer than a straight one between the same two, so you are engaging more metal. More important is the fact that the natural curve twists the shaving out rather than strictly lifting, as I mentioned above. Same principle applies when working final surfaces on bowls. Less lift, less rip. By skewing the gouge to the direction of travel you are able to use that longer contact area to hold a good reference on where you've been to keep you going where you want to go. Easier to maintain a flat surface that way.

Your detail gouge can't get a lot of skew into the cut because of the uneven depth of metal, so you probably will do best with it on a wing with a pull cut.
 
No, a curved line (edge) between two points is longer than a straight one between the same two, so you are engaging more metal. More important is the fact that the natural curve twists the shaving out rather than strictly lifting, as I mentioned above. Same principle applies when working final surfaces on bowls. Less lift, less rip. By skewing the gouge to the direction of travel you are able to use that longer contact area to hold a good reference on where you've been to keep you going where you want to go. Easier to maintain a flat surface that way.

Your detail gouge can't get a lot of skew into the cut because of the uneven depth of metal, so you probably will do best with it on a wing with a pull cut.

Two curves touch at a point. A curve and a line touch at a point. The wood surface is a curve , a gouge edge is a curve, and the skew straight ground Is a line.
The contact area is more or less the same on a light cut.


Al
 
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Huh? Does not compute. From entrance to exit - distance x - longer by the curved route.
 
I kind of agree with Al. Although mathematically there is a difference I think it's so small that for all practical purposes the chip coming off is the same size if the skew and spindle gouge are about the same width.
When I switch to a smaller gouge with a more rounded tip the chip coming off is thinner (width wise) and I think that's why I get less chip out of problem woods using the smaller spindle or detail gouge.
I have a huge spindle gouge (2" I think) and it almost always gives me more tearout than my skew which is 1 1/4". I think this is at least partly because the skew is sharpened at a 35 degree angle and the spindle gouge at 45. I can take my spindle roughing gouge which is sharpened at 45 degrees and get a cleaner but. I believe this is because it has more U shape to it than my big gouge and therefore takes a narrower chip.
 
Sounds like you're back to exchanging ridges and bumps for less tearout. Don't have to if you skew the gouge to take advantage of the progressive cut. You end up with a wider, though thinner shaving. You seem to know that it's not the sharpness angle - unless you really get it acute - that counts, but the radius of the curve. Just have to exploit that after some experimentation with degree of skew.

Watch the gouge working here as the corners come off and the piece regularizes. Wide, feathered shavings. They twist, which, as we know, is the sign of a progressive cut. What you're after, though a lot of people spin the piece so fast they can't feed fast enough get a long shaving.

http://s108.photobucket.com/albums/n28/MichaelMouse/?action=view&current=PeelandPare.mp4
 
MM on these woods I have skewed the damn thing every which way you can skew it. It lifts the fibers out on those bad places. It's not like your typical tearout problems. These are areas that sort of pluck out of lift out and it doesn't seem to matter how sharp the tool is or necessarily the angle you approach the cut. Am I getting little ridges, no, I control the feed rate so it's just as smooth as my wider gouges. The difference is it doesn't pluck out the wood on those bad areas.
 
MM on these woods I have skewed the damn thing every which way you can skew it. It lifts the fibers out on those bad places. It's not like your typical tearout problems. These are areas that sort of pluck out of lift out and it doesn't seem to matter how sharp the tool is or necessarily the angle you approach the cut. Am I getting little ridges, no, I control the feed rate so it's just as smooth as my wider gouges. The difference is it doesn't pluck out the wood on those bad areas.

I can sympathize with you, John..........

The one rule that is true for woodturning, is different pieces of wood require different ways to get a good cut....In other words, if it worked this time, it might not necessarily work as well the next time, for another piece of wood.

I have experienced the same kind of tear-out on bowls using gouges on the exterior long grain. At the point where the wood grain is going exactly the same direction as the cutting edge progression is. A little "waviness" in the grain here would do wonders, but we have to deal with the cards we're dealt. The solution is to get an ever increasing fineness of cut until the tear-out no longer exists......or, is so small that attention to sanding is the next logical step. But, of course, that is much easier said, than done.....🙁

If we were machines, we probably could do a little better in this one little aspect, but we are human, and understanding that is important. (Being human also means we are capable of that creative artistic touch that no machine can EVER create.) Anyway, since our bodies aren't ridged pieces of steel, we only have a certain level of dexterity, and the ability to guide a tool through a cut varies with each individual. We can increase the odds by knowing what the limitations of tool shapes are, presentation, sharpness of edge, polishing tool shafts and tool rest surfaces........but, in the end, it's how well all of that knowledge is applied through your hands. I'm probably not making any sense at all, except to those who don't need to learn what I'm trying to say anyway........because they have already "arrived"!

When we run into these tear-out issues, there is a series of things to do......try this, and if that isn't the solution......then try that........and then, this......etc, etc. I think most can relate to that aspect of it. Don't let the frustration of failure get the best of you......keep doing something different, because there is a way to solve most any issue.

I've said this before, and I suspect I'll get howls of disagreement from the usual people........but, if all else fails, a SCRAPER is what will give the absolute finest cut that can be had. It takes knowledge and patience......but, the particles of shavings can be so small that it's hard to tell them from pure dust......but, they are indeed shavings. It takes constant truing of the edge, and knowing just how to present that edge, and SLOW deliberateness.......but, it also takes something that serves to illustrate that we are not all equals.......and that is your ability to use the grey matter, and your eyes, and your ears.........and, process all of that information THROUGH your body, shoulders arms, and hands.

There's no way to tell anyone what I'm trying to say........it cannot be taught. It can ONLY be learned through hands on application......and a logical and accurate contemplation of the input. No matter how intelligent, or hard one tries........some of us will never "get it", because just as with seemingly equal pieces of wood, we are all different in ways that may not be evident on the surface.

ooc
 
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.but, if all else fails, a SCRAPER is what will give the absolute finest cut that can be had. It takes knowledge and patience......but, the particles of shavings can be so small that it's hard to tell them from pure dust..
I couldn't agree more as I said in post 3.

Some timbers will not cut cleanly with a skew or gouge.
 
So we return to my original post. Either get so low a pitch you can slice or go so high you're scraping. Same as if the wood were flat. I guess when you get down to it, an edge is an edge and wood is wood.

Still, even on the flat stuff with the gnarly multidirectional grain, I find myself reaching for the low angle smoother rather than the York pitch. I suppose John's narrow shaving detail gouge is the equivalent of the toothed blade, which doesn't take big chunks, but requires extra work to get smooth. Some day, a Lie Nielsen # 85 ....
 
I couldn't agree more as I said in post 3.

Some timbers will not cut cleanly with a skew or gouge.

Yes, you did Ian.......thanks for the reminder.

I have no doubt your understanding is similar to mine.

It is my intention to get the best surface I can with the gouge (or skew), and skip the need for scraping altogether. For the most part, no scraping will be required......but, nearly every one of my designs will require some amount of finish scraper work to "touch up" here and there. The whole idea is to eliminate coarse sanding. If one can start sanding at 220, or higher, I'd say that person has learned to control (and sharpen/prepare) his tools/equipment very well. If I recall right, I don't believe I've ever started sanding at 400, but have started sanding at 320 on the rare occasion. Most commonly at 220 and 180.......but, it would be insincere of me to not admit needing to start the occasional bowl at much coarser grits........150, 120, 100, and all the way down to 60-80 for really punky spalted wood with lots of tear-out.

Personally, I feel it's more difficult to master the scraper when the geometry and wood gets particularly demanding.......but, this gets back to how well one can move with the cut, taking the tiniest little slice of wood, with exactly the same body movement, over, and over, and over again. Some will find it more difficult than others. Absolutely nothing is easy, though......until experience hones the skill level. Even then, it's still not easy as pie.......but, it gets more pleasurable when you've done this a hundred times before, and have a little knowledge to back up the confidence that comes with experience.

ooc
 
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