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Possible end grain problem with bowl turning

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Forum topic by DW833 posted 04-14-2015 12:21 AM 1219 views 0 times favorited 19 replies Add to Favorites Watch
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DW833

191 posts in 1347 days


04-14-2015 12:21 AM

I purchased some bowl blanks at the Tampa woodworking show. There are green blanks purchased from http://www.woodturningblanks4u.com/.

The first blank I turned was a small piece of sycamore. I used a straight carbide tipped tool.
Got to a point where I couldn’t smooth the bowl any further. Some of the bowl is smooth, but most of it isn’t.
I’ve already changed the shape of the bowl from the original idea from trying to smooth it.

Viewing the surface it looks it could be end grain that is causing the rough surface. But since this is the first bowl I’ve turned, I’m not sure.

I’ve attached some pictures. Any thoughts on what my next step would be to smooth the surface?




19 replies so far

View TheFridge's profile

TheFridge

5765 posts in 951 days


#1 posted 04-14-2015 12:33 AM

Someone else more knowledgeable than I will surely comment, but as far as I know carbide is good for roughing but not so good for finishing.

Carbide will hold an edge longer but you can only get it so sharp. The opposite is true with HSS.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View johnstoneb's profile

johnstoneb

2145 posts in 1637 days


#2 posted 04-14-2015 12:35 AM

You said they are green blanks. I believe that they need to be put aside to dry after they are rough turned.

-- Bruce, Boise, ID

View HunterCreek's profile

HunterCreek

3 posts in 605 days


#3 posted 04-14-2015 01:27 AM

I haven’t worked with sycamore before, but that is more tearout than I would be happy with on a green blank. You are correct in assuming that the grain direction causes the tearout. You should be getting it both places where the the tool passes straight end grain. I think of it as from 90 degrees to 45 degrees off the grain line. At those two spots on the bowl you are making a climbing but which causes the chip-out. If you do much stock milling, you’ll get used to paying attention to the grain direction.

I’m not sure what you mean by “a straight carbide tipped tool.” But it sounds like it’s taking a scraping cut. A tool that makes a slicing cut like a bowl gouge or certain carbide tools will yield less tearout. Also, once you rough turn it a little thick and let it dry in some paper bags for a while, the wood will be harder and chip less.

Best of luck on your turning adventure!

~Hunter

-- Logic is the art of going wrong with confidence

View Bruyet's profile

Bruyet

34 posts in 607 days


#4 posted 04-14-2015 12:17 PM

I am a newbie myself, but I agree that the carbide tip is tearing out the grain. This is a very green sycamore bowl I turned Saturday. I wanted to try what I had read about turning green to the finished thickness, and seeing how the natural warping would affect the finished product. I did the entire thing with my bowl gouges. The finishing cuts were the size of eyelashes. It is less than 1/4” thick.

As you can see there are some tool marks to sand out, but they aren’t too bad. It lost 1/3 of its weight in two days. You can see some warping on the edge.

View Wildwood's profile

Wildwood

1886 posts in 1599 days


#5 posted 04-14-2015 01:27 PM

Yes that is tear out or torn end grain.

Possible causes:
Wood species or that particular piece of wood itself prone to tear out!
Lathe speed to slow!
Rushing or forcing the cut with a dull tool!

Some pieces of wood even wet/green/dry just prone to tear out, so have to find the optimum lathe speed for tool using, taking lighter cuts not forcing tool into the wood and letting the tool cut normally clears up tear out or torn end grain. Some folks will saturate the wood with CA glue let it dry for couple minutes to harden torn end grain wood fibers before attacking it again.

Would look around town for those bundles of firewood sold for between $5 to $7 and buy some to practice on. From the pictures think your problem more a lack of experience/skill with the tool and lathe. To be fair carbide tools come with roughing & finishing cutters both take experience with them to get decent wood surface. Quality of some cutters better than others, but sometimes there is just no substitute for conventions turning tools!

-- Bill

View Nubsnstubs's profile

Nubsnstubs

826 posts in 1195 days


#6 posted 04-14-2015 02:36 PM

I agree with Bill’s comments. My first thoughts were, too slow, dull tool, and wet or green wood prone to tearing out.

California Pepper is one that when soaking wet, has exactly the same type of tear out you’ve pictured. It doesn’t matter what speed you turn nor the condition of the tool, it’ll look just like that until it dries. Then, you still get tear out, but it’s manageable. ............... Jerry (in Tucson)

-- Jerry (in Tucson)

View LeeMills's profile

LeeMills

271 posts in 766 days


#7 posted 04-14-2015 03:31 PM

I haven’t had too much problem with sycamore even when just cut. But things happen.
Carbide should cut a lot cleaner going side grain. I would guess that you are cutting straight into the side, this would put the tool perpendicular to the bed of the lathe. Try making small cuts (maybe 1/8” deep) moving from the tailstock to the headstock. This will be cutting into side grain.
When I started I did a lot of “poking” at an item instead of moving by body to make the cut. Cutting with your body is called Stance or Dancing With The Lathe.
Here is a link to Stuart Batty videos; three of which are on stance. I am not sure which of the three are for spindle orientation and which are blank orientation but you will know quickly enough as they are only about 12-15 minutes each.
Just scroll until the three on stance show up.
https://vimeo.com/woodturning/videos/sort:alphabetical/format:thumbnail

-- We cannot solve our problems with the same thinking we used when we created them. Albert Einstein

View DW833's profile

DW833

191 posts in 1347 days


#8 posted 04-14-2015 04:29 PM

Thanks for all the feedback.
Bruyet, what size and grind of bowl gauge did you use
for the finish cut?

View Bruyet's profile

Bruyet

34 posts in 607 days


#9 posted 04-14-2015 05:01 PM

3/8”. I believe it is a 40 degree. I will check when I get home.

View Rick M's profile

Rick M

7922 posts in 1845 days


#10 posted 04-15-2015 01:30 AM

That is really bad tearout, can’t blame that on carbide. I have no experience with sycamore but I suspect your problem is speed/technique. The guys above have already given good advice.

-- http://thewoodknack.blogspot.com/

View DW833's profile

DW833

191 posts in 1347 days


#11 posted 04-15-2015 01:54 AM

Wildwood,
There are different types of CA glue. Super Thin, Thin, Medium, etc. Which type would be good for this task?
I’m thinking of purchasing Pentacryl Wood Stabilizer. Do you think it would be ok instead of the ca glue?

View Wildwood's profile

Wildwood

1886 posts in 1599 days


#12 posted 04-15-2015 12:49 PM

DW833, a sharp tool and taking light cuts only way to clean up what you have there now. That might also include another design change.

The time to use CA is when you first begin to see some tear out. Goal is to stiffen wood fibers so can slice them off. There is no one type of CA glue (med, thin, thick) for every situation so a good compromise might be medium CA to have on hand.

I am not a big fan of Pentacryl Wood Stabilizer because instructions & disclaimer trouble me and believe learning curve pretty steep & expensive. Forget hype about just brushing product on the surface of wood to cure all evils! You could also try brushing on rubbing alcohol, mineral oil, mineral spirits, or water for lot less money. Submerging wood in the product about the best op. Again feel instructions & disclaimer a big problem.

“DISCLAIMER: Being that wood is a natural material and is susceptible to varying
degrees of shrinkage, reaction, deterioration and because of varying climatic conditions, varying experience of the user and may be applied under conditions beyond our control, as seller, we make no warranty expressed or implied as to this material or its use. All information stated herein is accurate to the best of our knowledge and is based on thorough testing.”

I would rather you look into buying an inexpensive HSS bowl gouge with traditional 45 degree fingernail grind to help you learn to turn. Since have no idea of lathe size recommend either 3/8” or ½” or both size bowl gouges.

http://www.pennstateind.com/store/LX210.html

http://www.pennstateind.com/store/LX220.html

-- Bill

View Wildwood's profile

Wildwood

1886 posts in 1599 days


#13 posted 04-15-2015 01:12 PM

Here is a roughed out Poplar bowl. Did not matter how many trips to the grinder to touch up the tool edge the wood gave me fits. Long story short after trying everything could think of put that bowl aside to dry. First bowl turned with my new Thompson bowl gouge.

After couple month’s final turned, applied finish and gave it to my sister. You could not see any torn end grain or tool marks. Do not have a final picture of that completed bowl but have similar styles posted on my projects page. Some of that Poplar harvested after a storm also gave me fits. Went through the bottms of a few trying to get rid of torn end grain, and then had some with no problems what so ever!

-- Bill

View LeeMills's profile

LeeMills

271 posts in 766 days


#14 posted 04-15-2015 01:26 PM

It probably would not work on wet/green wood but for the second turning I use thinned shellac to stiffen the fibers. It is cheap and dries enough to keep turning in about 10 minutes. It only soaks in about 1/16” so several coats may need to be applied.
For a bowl on the outside you cut from the smallest diameter to the largest in order to cut with the grain. Even though the sides of yours are steep you may have been cutting against the grain?

-- We cannot solve our problems with the same thinking we used when we created them. Albert Einstein

View LeeMills's profile

LeeMills

271 posts in 766 days


#15 posted 04-15-2015 02:00 PM

Here is a clip by Lyle Jamieson on cutting the bottom of a bowl. You can skip over to about the 4 minute mark.
Notice he is cutting with the grain, cutting towards the headstock.
It doesn’t matter if you are using a parting tool, carbide tool, or gouge, this direction will give the cleanest cut.
https://www.youtube.com/watch?v=DfZcQ3xFnI4

-- We cannot solve our problems with the same thinking we used when we created them. Albert Einstein

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