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Tear Out in end grain...

D

Devin Howard

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Aug 4, 2008
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I have turned 50 to 60 bowls now and while I have become much more confident in the process..... I cant keep the tear out... well... out. It really has made for a LOT of extra sanding... So in short... I need help.

Thanks.

Devin
 
I posted this in the Tips and Techs page but thought I would put it here.

I am having a lot of trouble with tear out on the inside of my bowls. I hate sanding!! ... SO ... I need some help with this please.
 
Devin.......

There are those who avoid this by making segmented bowls, sticking with spindle turning, or even designing bowls with simplicity of sanding in mind, but I don't think this is the answer you are looking for.

The question of how to eliminate tear-out on end grain is one that will frustrate even the best of turners! 😀 I doubt there is a single turner that can honestly say they never have any tear-out........ever! Many of them do find ways to minimize it, and on some efforts a few of them eliminate it entirely.

With such limited information you've given, the best advice you will get is to have sharp tools. I guess that would be a good place to start......

Can you tell us a little about your sharpening techniques and procedures?.....tools you are using?

ooc
 
Some will say your tools aren't sharp enough, some will say you need to work on your technique, but my experience is that it's never completely avoidable. Wood species, figure and how dry it is will have just as much effect as using a not quite sharp enough gouge. Dry wood will always tear out more than wet. Some softer woods will tear out more than harder, but that's not always the case. Overall, I'd put maple, cherry, sycamore and beech (there's probably a few more) as the lowest in tear out overall. Dry oak, bubbinga and anything with really high figure are at the other end. The first photo is a bowl about 8" in diameter of dry curly chestnut. The outside turned fairly well, but finishing the inside took a lot of 60 and 80 grit sanding. The second, dry hard maple had tear out where the figure reversed itself in several places, but not on the end grain. The third is a 24" bubbinga piece that took me seemingly forever to sand out the inside since it's so hard a wood, has to be dry to get into the US, and is so large.
 

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tear out

Another thing is to make LIGHT passes with a newly sharpened tool. What has helped me on some is to reverse the cut and go downhill instead of uphill with the last few passes. Works on some woods and not others. Viva la difference!!! Gretch
 
Sharp tools, light cuts, bevel riding, curve all the way to the bottom. Ride the bevel from rim to center of the bottom.

I often use a 1/4 bowl gouge for the first 2 inches inside the bowl.
This tool forces the light cut and has very little bevel drag. It is a great finishing tool.

You probably cannot eliminate tear out. You can reduce it to where it is hard to see and easy to sand. With proper technique most of the cutting force is toward the bottom of the bowl so fibers get cut cleanly because they are supported by fibers behind them. When sanding stop the lathe and work the tearout sections then run the lathe a bit to blend them in.

Rough turned dried bowls warp and the diameter is largest measures to the endgrain sides. When you are returning a dried bowl the roughing cuts come out into air as you come to the end grain you lose the bevel for a tiny bit and tearout occurs. aggressive roughing cuts make more tearout. light cuts, sharp tools minimize this. having a 1/4 of wall thickness to turn away after the inside is round is usually enough to cut below the tearout. remove this 1/4 inch with
1/8, 1/16 and 1/32 cuts.

Learning the shearing cut with the side ground bowl gouge made an enormous improvement for me on the insides of bowls

Happy turning,
Al
 
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I've been playing a lot with tearout problems the last year. I was given some very old, really dry box elder, and it's too nice to not turn. It tears out on the end grain if you look at it wrong. Here is what I do, and it works on all woods that I've tried. Tearout is caused by the wood being pulled out instead of cut off. You have to figure out how to make the tool cut the wood. I'll go through the steps that I have found to work. I'll put these in the order I try them.
First, obvious, sharpen the tool. I usually use a tool straight off a 100 grit wheel but will occasionally use a fine diamond hone (about 600 grit) on the outside of the bevel and a diamond fishing hook sharpener on the flute.
Second, decrease your feeding pressure. I find most tearout (particularly on new turners) is due to pushing the tool too hard through the cut. Lighten up your grip on the tools and try to feel the cut. You have to move the tool slower than you think to really get a clean cut. Increasing the speed of the lathe can accomplish both. Increasing the speed of the lathe lets you move the tool at a more comfortable rate while still taking a small bite out of the wood.
Third, Use a tool with a sharper angle to the edge. Most bowl gouges are sharpened to about 50 to 65 degrees. Try one at 40 degrees if you bowl is shallow enough. I like the Stewart Batty grind for this but A spindle gouge works great. My spindle gouges are ground at 40 degrees. The best tool I've found for bowl interiors that have tearout problems is the Hunter tool. The Hunter tool has a counter sunk lip which makes the cutting edge around 25 degrees. If you rub the bevel of the tool and tilt it about 45 degrees to the direction of the cut it will cut off the tiniest ribbons of shavings even in tearout prone woods. You do have to really slow down your feed rate and speed up the lathe to get this clean cut but it's worth it.
Ok, you've tried all of the above at hasn't worked well enough. I reach for the Johnson's paste wax. You could use any wax you have or sometimes simply spraying it with water works. This acts as a lubricant will usually is as far as I need to go to prevent tearout.
Worst cast scenario. Wood that is spalted, getting punky or downright rotten is the most difficult and the above techniques may not work. I soak the wood in Lacquer that has been thinned 50/50 with lacquer thinner. This will actually penetrate all the way through punky wood. It may take several coats to really harden the wood. Let it dry. This has always worked for me. For small areas I might use Thin CA glue. It dries faster but is a lot more expensive than the lacquer. The lacquer can clog up sandpaper so I keep a file card handy to clean the discs when sanding. I have not had a problem with compatibility of finishes with this technique.
I've also read from very reliable sources that a soaking in a 50/50 mix of white glue and water will work. Soak for several hours and let it dry overnight.
In an absolutely worse case where the wood is really rotten I use a product called System 3 Mirror Coat. It is a very clear epoxy used to finish bar tops. I buy it at Woodcraft. This stuff becomes extremely viscous when it is going through the thermal setting process. I've had it actually run all the way through the pores of red oak and pine vessels. It is an epoxy so it is quite hard when dry and you can cut through it easily and it sands very well.
 
Try changing tools. As mentioned, along with the obligatory "sharp," (as if anyone ever said to use a dull tool) you might want to go to a longer bevel to get under the shavings and use a tool that will allow you to get a good skew into the cut, which also effectively reduces the sharpness angle. You also want to get the idea that "riding the bevel" means a zero clearance angle out of your mind. The tool can have a good clearance angle while still guiding on the bevel. It just doesn't guide to the heel, but parallel to the edge.

In my house that cut does not mean a "bowl" gouge, but a broad sweep forged type which gives almost no lift to the shavings I'm taking. That's a sure sign that they're not ripping up and out on the end grain. With green wood the shavings are continuous, folding up against the opposite wall as you see here. http://i35.photobucket.com/albums/d160/GoodOnesGone/Forged-Peel-Inside.jpg

With dry wood you can do the same, as you see here in motion. http://s108.photobucket.com/albums/n28/MichaelMouse/?action=view&current=CherryPeelIn.flv Shavings are still long, but they aren't quite thick enough to avoid breaking on the endgrain areas. If you get dust and chips, you're cutting wrong.

Answer as to why it works is simple. The picture below shows a "bowl" gouge in cutting position as some like to do. Beside it is the other tool, resting with full support on the toolrest, which when coupled with the roll and skew, causes the shaving it's creating to hold it on its bevel in a controlled depth of cut. Your desired shaving is smooth and thick on the leading side, thin and feathered on the trailing side. These are some broad shavings taken on an interrupted surface by a roughing gouge. http://i35.photobucket.com/albums/d160/GoodOnesGone/W-ShavingsDemo.jpg
 

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Some woods are much worse than others about tearing out, but in all cases having very sharp tools and good tool technique will make a big difference. One of the most common technique-related reasons for tear-out is when the tool is making a scraping cut rather than a slicing cut. Trying to go too far before resharpening a tool probably ranks a close second.
 
What a great thread!

I'm planning on finishing several roughed bowls next week, and I'm sure this info will help me out quite a bit.

I rough turned a 14" Big Leaf Maple Burl bowl last night. It's my biggest so far since I've just upgraded from a mini (what a difference a few hundred lbs makes). The blank was full of figure and burl on one side, and plain on the other. The tear-out on the pretty side was pretty bad, and barely noticeable on the plain side. I can't say I'm looking forward to finish turning it, but this thread will help when I start searching "tear-out."
 
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