Turning of Cherry, mostly open bowls, but other shapes as well, I can't seem to find the right technique or tool to get a clean cut at the 2 locations when cutting against the grain. I have over 100 rough turned pieces, now dry, and no matter which tool I use, or what angle I try, I get tear out that makes for a lot of sanding I would rather not have to do. My tools are sharp. Any suggestions?
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Tear out
- Thread starter John Volcko
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I
John,
I am a huge huge fan of hands on instruction either in a formal class or a mentoring session with a local club member.
I can't see from here what the problem is.
Heavy cuts will cause some tear out just because the cut wood is still connected to some uncut wood.
If I cut a 3/4" wide shaving when roughing there will be tear out.
If I cut a 1/64 you can't see tearout.
Scraping with the gouge will cause more tearout than slicing
Cutting with a gouge with the bevel riding will leave a clean surface.
Gouge with dips and bumps along the cutting edge will cause tearout and catches
The gouge should be ground so that the cutting edge is a continuous convex curve wing to wing
Cutting so that uncut fibers support the cut is critical.
On a face grain bowl this is foot to rim on the outside, rim to bottom center on the inside.
When returning dried bowls the easiest to return are those with a smooth surface.
I try to get a clean surface with no ridges, dips or tearout on the rough turned bowl.
When I return there should be two lines on the outside edge that have no wood removed to make it round in the original shape.
Can't help without seeing what you are doing.
Al
John,
I am a huge huge fan of hands on instruction either in a formal class or a mentoring session with a local club member.
I can't see from here what the problem is.
Heavy cuts will cause some tear out just because the cut wood is still connected to some uncut wood.
If I cut a 3/4" wide shaving when roughing there will be tear out.
If I cut a 1/64 you can't see tearout.
Scraping with the gouge will cause more tearout than slicing
Cutting with a gouge with the bevel riding will leave a clean surface.
Gouge with dips and bumps along the cutting edge will cause tearout and catches
The gouge should be ground so that the cutting edge is a continuous convex curve wing to wing
Cutting so that uncut fibers support the cut is critical.
On a face grain bowl this is foot to rim on the outside, rim to bottom center on the inside.
When returning dried bowls the easiest to return are those with a smooth surface.
I try to get a clean surface with no ridges, dips or tearout on the rough turned bowl.
When I return there should be two lines on the outside edge that have no wood removed to make it round in the original shape.
Can't help without seeing what you are doing.
Al
Last edited:
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Back side of the endgrain is often a problem area on face grain bowls
On the outside of a bowl when cutting foot to rim with the bevel riding most of the cut is toward the headstock and clean because each fiber cut has wood behind it supporting the cut so that the fiber is cut instead of bending or pulling out.
A small cutting component is in the vertical direction perpendicular to the ways of the lathe.
As the bowl rotates the small amount of perpendicular cut will cut cleanly from the middle of the side grain to the middle of the end grain because each fiber is supported with wood behind it.
As the bowl rotates to the backside of the endgrain there is only air behind the small amount of vertical cut and the fibers can pull out and break instead of cutting cleanly.
Whenever Checking the smoothness of the cut check the two backside of the endgrain areas. That will be the worst spot.
If tearout is hard to see and just feels a little rough, shear shaping will clean it up.
I use an Ellsworth ground gouge. If I'm getting a detectable tearout with the bevel riding push cut, I switch to a pull cut on the wing.
The wing is a much sharper angle among 30-25 degrees which makes a cleaner cut than the 60 degree angle at the nose.
During the cut the angle of the wing is 80 to 50 degrees to the rotating wood giving almost no cut in the vertical direction.
The pull cut with the handle low will give the cleanest cut I get with a gouge.
I use it all the time on natural edge bowls and it will usually cut the bark cleanly. There is nothing but air on the other side of the bark.
Al
On the outside of a bowl when cutting foot to rim with the bevel riding most of the cut is toward the headstock and clean because each fiber cut has wood behind it supporting the cut so that the fiber is cut instead of bending or pulling out.
A small cutting component is in the vertical direction perpendicular to the ways of the lathe.
As the bowl rotates the small amount of perpendicular cut will cut cleanly from the middle of the side grain to the middle of the end grain because each fiber is supported with wood behind it.
As the bowl rotates to the backside of the endgrain there is only air behind the small amount of vertical cut and the fibers can pull out and break instead of cutting cleanly.
Whenever Checking the smoothness of the cut check the two backside of the endgrain areas. That will be the worst spot.
If tearout is hard to see and just feels a little rough, shear shaping will clean it up.
I use an Ellsworth ground gouge. If I'm getting a detectable tearout with the bevel riding push cut, I switch to a pull cut on the wing.
The wing is a much sharper angle among 30-25 degrees which makes a cleaner cut than the 60 degree angle at the nose.
During the cut the angle of the wing is 80 to 50 degrees to the rotating wood giving almost no cut in the vertical direction.
The pull cut with the handle low will give the cleanest cut I get with a gouge.
I use it all the time on natural edge bowls and it will usually cut the bark cleanly. There is nothing but air on the other side of the bark.
Al
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Tear out can be caused by several things. Of course, sharp tools is one, well dull tools cause more tear out. Presentation is another, which means how you cut the wood. Scraping cuts (cutting edge is at 90 degrees to bowl rotation), in bowl orientation leave a much more coarse surface than shear cuts. Shear cuts cut more cleanly, meaning the cutting edge is at an angle to the spin. The higher the angle, the cleaner the cut most of the time. How fast/hard you are pushing on the tool is another part. Roughing cuts can be done as shearing cuts or scraping cuts, but especially for me, I am cutting as fast as the lathe will let me, so generally the wood will show more areas where I am tearing rather than cutting. With finish cuts, you cut much more gently/slowly so the wood actually cuts before it tears. After that, it can depend a lot on the wood. I have only turned a few pieces of eastern black cherry which is a prized furniture wood. It cuts very well. I have gotten a number of ornamental cherry out west here, and it is generally rather stringy. Now, for you, the hard part is figuring out how much all of the above fits into the cause of your tear out. I always start a finish cut with a freshly sharpened tool.
They still haven't invented transporters yet, so I can't make an instant trip out there for a hands on session, which would do a lot for figuring out what is causing the tear out. Most clubs will have mentors, and of course, there are a lot of videos. I have a number, aimed mostly at bowl turning. Head to You Tube and type in robo hippy.
robo hippy
They still haven't invented transporters yet, so I can't make an instant trip out there for a hands on session, which would do a lot for figuring out what is causing the tear out. Most clubs will have mentors, and of course, there are a lot of videos. I have a number, aimed mostly at bowl turning. Head to You Tube and type in robo hippy.
robo hippy
Have you tried rubbing candle wax on the tear out area. I regularly use this to help overcome such problems.
I did have a very dry piece of Koa, and it had nasty tear out no matter what I did. I misted it with water. let that sit for 60 or so seconds, then VERY GENTLY turned off the wet stuff. It took a couple of times to get it down to 'sandable'. Others use oil, or oil/wax mixes. I think this is mostly used on dry wood.
robo hippy
robo hippy
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I am another water first. I use a plant mister.
I water is often enough to swell the fiber tight enough to support the cut.
For more stubborn wood I use a thin shellac. Twice the alcohol.
I water is often enough to swell the fiber tight enough to support the cut.
For more stubborn wood I use a thin shellac. Twice the alcohol.
Robo, some woods are just mean. Koa is mean. Anyone who says they love turning Koa is lying or just has not turned enough of it. It is very unpredictable and very tough to get a clean cut on. As a boy who has turned thousands of Koa bowls I just know to take it slow, really slow down the feed rate and do not hesitate to go to the grinder.
As for this thread one of us would need to be standing with you and see and feel your tools and watch how you put the tool to the wood. A mentor from a club is the best advise given here.
As for this thread one of us would need to be standing with you and see and feel your tools and watch how you put the tool to the wood. A mentor from a club is the best advise given here.
Not only that, but some examples of a species just turn more difficultly than with others! One in particular for me, is quilted Maple. Sometimes the swirly grain pattern is much more difficult to get a clean cut than at other times. It's not you, it's the wood, and not just any piece of wood......it's THAT piece of wood!
Kelly Dunn is right, the only way to be sure, is to be there with you and observe your technique first hand.
All of us here have seen this frustration being aired over and over again in the forums.....and, right down to the very last one, they always say their tools are sharp, so that isn't the problem. This isn't a statement about the OP John Volcko, but it is a statement about this kind of thread in general. Some turners only think their tools are sharp.....and, as Kelly Dunn points out: Some turners need to resharpen a little more often than they do.
ko
Well, it was and is the only piece of Koa I have turned. Cottonwood is another nasty one that is extremely difficult to cut clean. It stinks too. I do have another blank or three of that Koa, just haven't gotten to it yet. Maybe I will donate to an auction. Kind of hate to do that to friends though... Probably the worst thing I ever tried to turn was a piece of palm that was a side grain orientation bowl blank..... Many bad words were said....
robo hippy
robo hippy
john lucas
AAW Forum Expert
Tearout can be a problem that is hard to identify without looking over your shoulder. What I do is first and foremost try a freshly sharpened tool and a very light forward pressure on the cut. If that doesn't work I try to use a tool that has a sharper (more acute) cutting angle. My normal bowl gouge is about 55 degrees but I have one ground at 40 that will work most of the time. If the bowl is too steep for the 40 degree gouge I will often go the the Hunter Osprey which is a carbide tool with a 27 degree cutting angle tip. That usually works. if that doesn't work I will either mist the part with water or rub lacquer thinned about 50/50 with lacquer thinner.
Most of the time a freshly sharpened tool followed by light cuts and light forward pressure and trying to position the gouge so the wood is passing the cutting edge at a shear angle will work. Sometimes you get a piece that fights you no matter what you do. If you have reverse try running the lathe in reverse and cutting from the opposite side. This will usually give you tearout in the two opposite corner from the original but sometimes it will be less and make it easier to remove. Worse case scenario. stop the lathe and attack it with a curved cabinet scraper. Cut all the tearout away and then feather out the divot you make so that when you sand it will kind of blend in and no one will be wiser.
Most of the time a freshly sharpened tool followed by light cuts and light forward pressure and trying to position the gouge so the wood is passing the cutting edge at a shear angle will work. Sometimes you get a piece that fights you no matter what you do. If you have reverse try running the lathe in reverse and cutting from the opposite side. This will usually give you tearout in the two opposite corner from the original but sometimes it will be less and make it easier to remove. Worse case scenario. stop the lathe and attack it with a curved cabinet scraper. Cut all the tearout away and then feather out the divot you make so that when you sand it will kind of blend in and no one will be wiser.
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I'm still fairly new to turning. That said, being in Alaska I turn a lot of soft local woods that just love to tear out. I'll second much of what has already said as helping me.
I'm also a fan of honing. I have a CBN hone with a flat and two radiuses (one smaller, one bigger) that works great. I also move to a smaller gouge sometimes for finish cuts.
I know my finish cuts have improved too since I started moving my body with the tool, not just standing like a statue and moving the tool with my arms.
All that said, I'm finding that sometimes I can't do better than starting with 120 grit, and occasionally with 80, as painful as that is.
Best of luck, and I'll be watching this thread.
I'm also a fan of honing. I have a CBN hone with a flat and two radiuses (one smaller, one bigger) that works great. I also move to a smaller gouge sometimes for finish cuts.
I know my finish cuts have improved too since I started moving my body with the tool, not just standing like a statue and moving the tool with my arms.
All that said, I'm finding that sometimes I can't do better than starting with 120 grit, and occasionally with 80, as painful as that is.
Best of luck, and I'll be watching this thread.