Tear Out - Woodworking Talk - Woodworkers Forum
 
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post #1 of 9 Old 01-15-2012, 03:53 AM Thread Starter
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Tear Out

I've been making pens and pencils lately due a lack of tools. I'm starting a lot of overtime so I won't have any woodworking time in the near future and don't want to spend $1,000 on tools only to look at them for a month. Anyway, I've noticed that I seem to get some tear out on some, but not all of my pens. I'm still using just the 1/2" skew and taking nice light cuts. Here's a pic of what I'm talking about.

Tear Out-dsc00454-2.jpg

If you look at the "cap" section you can see it best. I have about 20 coats of CA on it, but you can still see the little spots of tear out. Or at least I think it's tear out. Not all of my pens do that. I have several that are smooth as glass, but then I get one like that.

Am I doing something wrong, or is that just something you get with some woods? I think that wood makes beautiful pieces, but I'd love to get those spots out.
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post #2 of 9 Old 01-15-2012, 07:05 AM
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Some woods are just prone to tearout. Possible solutions.
Change the angle of attack of the cutting edge. More perpendicular to the work means a slower but cleaner cut but not always. Sometimes a more parallel cut works better.

Slower feed rate. Anytime I have tearout I first assume sharpness of course but the second biggest reason it pushing the tool to fast for the speed of the lathe. Speed up the lathe, slow down your feed rate or both.

On occasion I have found that a smaller cutting tip like that of a small spindle gouge cuts cleaner on tearout prone wood. I have not been able to figure this one out but it works. I use a 3/8" spindle gouge with a somewhat pointy tip. See the beginning of the video I posted above to see the 1/2" version of that tool to understand the tip shape.

Soak with thin CA glue or thinned lacquer. The thin CA glue solved that problem with a very difficult Black Palm piece of wood that wanted to lift the fibers of the wood no matter which tool I used.

Sand it to submission. This requires careful work to not change the shape. You might try gluing sandpaper to a stick. I do that with 3M super 77 spray adhesive.
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post #3 of 9 Old 01-15-2012, 05:27 PM Thread Starter
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I do have a small spindle gouge. I could give that a try when I get close to the desired finial diameter. Haven't used it in a while so a good sharpening is in order.
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post #4 of 9 Old 01-15-2012, 06:04 PM
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I had a similar problem trying to turn a pen out of a piece of black palm. I'm a complete noob at the lathe so I probably shouldnt have been messing with black palm but it looked so sweet, I had to give it a try. What worked for me was speeding the lathe up as fast as it would go and taking very light cuts with a 3/8 spindle gouge with a somewhat pointy tip like john lucas was talking about.

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post #5 of 9 Old 01-15-2012, 06:27 PM Thread Starter
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I've been turning pens at about 2500 rpm. The lathe does go up to I think 3800, but that seems awfully fast. Going to give it a try and see what happens. Maybe that, and using the small spindle gouge will do the trick.
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post #6 of 9 Old 01-17-2012, 03:34 PM Thread Starter
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I increased the rpm a bit, to about 3200 and instead of using the skew with a cutting angle around 45 degrees, I adjusted the angle to almost about 80 degrees to the axis of rotation and took some very light cuts. Sorry, I didn't use a gouge. I seem to have developed a liking for the skew. That seems to have done the trick. I got no tear out at all on the next pen. I thought that might just be a fluke, so I tried a third pen, and again got no tear out again. Pens are looking much better now, even with woods that gave me problems in the past. I even tried a piece of black palm and had no problems keeping it smooth. Thanks for your advice.
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post #7 of 9 Old 01-18-2012, 11:39 AM
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Check into negative rake scraping. Here's a link www.negativerakescraper.com
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post #8 of 9 Old 01-18-2012, 03:10 PM
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I don't believe negative rake scraping will ever give as good a finish as a skew used at the best angle for a particular wood. Possible on incredibly hard stuff like Ivory and bone, maybe blackwood. I could be wrong but I've done a lot of work with both tools and with rare exceptions the skew is the best finish.
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post #9 of 9 Old 01-18-2012, 08:06 PM
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A skew will work great for the outside of a piece and for a pen as in this case, but how would you use a skew for an inside curve like inside a bowl? The Skew also takes a lot of practice to master.
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