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Smooth Surface inside a Bowl (Read 2,606 times)
 
robo_hippy
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Re: Smooth Surface inside a Bowl
Reply #15 - Feb 4th, 2018 at 10:59am
 
The inside of the bowl is much more difficult to turn than the outside, in part because you can't really see any profile, and have to rely on your fingers to feel where bumps and dips are.

The one handed push cut for the inside of the bowl is a great skill to practice to learn "the bevel should rub the wood, but the wood should not know it" technique. One hand on the handle, and the other very lightly resting on the tool shaft, not the tool rest, or not on the tool at all after you start the cut.

Shear scraping is an excellent way to remove just about all of those marks ( I have that video is up in the video section here, and more on bowl turning here and on You Tube), though a negative rake scraper is a little better for going across the bottom.

The 'step' method refers to turning out the inside of the bowl. Mostly this is a way to deal with how the walls will flex and wobble (especially if you are pushing too hard) as you turn out the inside of the bowl. Not much of a problem on a 6 inch diameter bowl. and can be a major problem on 16 inch bowls. So, when you turn out the inside of the bowl, you do finish cuts in steps, about an inch or so at a time, then the next inch or so, blending in the start/stop points. This will leave a series of steps on the inside of the bowl. It makes it easier to pick up where you left off on roughing cuts.

With any piece that has defects, more so than good sound pieces, develop the habit of standing out of the line of fire. Greatly reduces the chances of getting hit by flying chunks of wood.

robo hippy
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Derik Mittag
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Re: Smooth Surface inside a Bowl
Reply #16 - Feb 4th, 2018 at 3:11pm
 
Jeff Vanden Boogart wrote on Feb 4th, 2018 at 10:37am:
Derik, I also use most of my own wood.  What I try to do is leave it in log form until I can get to it.  Then cut off what I can use that day and rough turn a few bowls, seal them, and put them on a shelf.  Small cracks I may treat with CA, but ones that develop large cracks go in the wood burner.
It's pretty hard to get wood from people/services cutting down trees around here...everything is claimed long before it comes down.  Seems like EVERYBODY has a pile of firewood behind the garage...LOL.   Putting the word out to friends and family, which they can extend to their friends, has got me some good wood.  Got a huge birch a while back, some good, but lots of storm damage.  The rotted, cracked sections we were rolling out to the curb.  A couple guys in a pickup truck stop...they wanted it.  They stood around waiting for us to finish...they wanted anything and everything we weren't interested in.  The sound of a chainsaw brings 'em running in no time...LOL


Only problem with leaving them in log form, borers will destroy all of my stock. I cut the logs into pieces and rough the pieces down to prevent that.

I mainly keep an eye out for fallen trees along public roads. There was a nice ash tree that had fallen down but someone got to it before I could.
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Derik Mittag
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Re: Smooth Surface inside a Bowl
Reply #17 - Feb 4th, 2018 at 3:14pm
 
robo_hippy wrote on Feb 4th, 2018 at 10:59am:
The inside of the bowl is much more difficult to turn than the outside, in part because you can't really see any profile, and have to rely on your fingers to feel where bumps and dips are.

The one handed push cut for the inside of the bowl is a great skill to practice to learn "the bevel should rub the wood, but the wood should not know it" technique. One hand on the handle, and the other very lightly resting on the tool shaft, not the tool rest, or not on the tool at all after you start the cut.

Shear scraping is an excellent way to remove just about all of those marks ( I have that video is up in the video section here, and more on bowl turning here and on You Tube), though a negative rake scraper is a little better for going across the bottom.

The 'step' method refers to turning out the inside of the bowl. Mostly this is a way to deal with how the walls will flex and wobble (especially if you are pushing too hard) as you turn out the inside of the bowl. Not much of a problem on a 6 inch diameter bowl. and can be a major problem on 16 inch bowls. So, when you turn out the inside of the bowl, you do finish cuts in steps, about an inch or so at a time, then the next inch or so, blending in the start/stop points. This will leave a series of steps on the inside of the bowl. It makes it easier to pick up where you left off on roughing cuts.

With any piece that has defects, more so than good sound pieces, develop the habit of standing out of the line of fire. Greatly reduces the chances of getting hit by flying chunks of wood.

robo hippy


Thank you much for that, I'll take a gander at the video
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Glenn Jacobs
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Re: Smooth Surface inside a Bowl
Reply #18 - Feb 5th, 2018 at 2:02pm
 
Derik, Robo Hippy is modest. Watch all of his vids and the ones from Bob Hamilton. (Bob passed away last year.) Some of the ridges could be a result of the vibration caused when cutting a bowl with cracks. Listen to the change of tune when cutting. Fill the cracks as soon as they appear will reduce the "shatter" and the vibration.

Glenn J.
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Don Stephan
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Re: Smooth Surface inside a Bowl
Reply #19 - Feb 5th, 2018 at 7:37pm
 
Apologies that I didn't think of this a few days ago.  Stuart Batty has a number of short videos on the Internet, one of which specifically addresses bowl gouge chatter.  Try
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If that doesn't find the videos search on the Internet using "Stuart Batty SB Tools" and look through the returns
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David Hill
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Re: Smooth Surface inside a Bowl
Reply #20 - Feb 7th, 2018 at 10:29am
 
Derek, nice bowl  I turn a LOT of Mesquite.  Good advice on the chatter toward the rim.  When I'm not lazy, I'll use a bowl steady, helps some to steady the wood flexing toward the rim.
Mesquite is my wood of preference, even though there are lots of other Texas trees that turn well.  I like it because you never know what's in a blank--it's a perfectly imperfect wood.
As for that crack, that one would not have deterred me in the slightest.  I use the cracks and grub holes as opportunities for inlay. If I have a concern--I'll either use CA or epoxy to protect me or the project.

Where are you located?  out of curiousity.
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Everyday liberating nice things from ordinary chunks of wood---and I like gnarly wood, the outcome is nearly always better than the start.
 
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Derik Mittag
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Re: Smooth Surface inside a Bowl
Reply #21 - Feb 7th, 2018 at 7:53pm
 
David Hill wrote on Feb 7th, 2018 at 10:29am:
Derek, nice bowl  I turn a LOT of Mesquite.  Good advice on the chatter toward the rim.  When I'm not lazy, I'll use a bowl steady, helps some to steady the wood flexing toward the rim.
Mesquite is my wood of preference, even though there are lots of other Texas trees that turn well.  I like it because you never know what's in a blank--it's a perfectly imperfect wood.
As for that crack, that one would not have deterred me in the slightest.  I use the cracks and grub holes as opportunities for inlay. If I have a concern--I'll either use CA or epoxy to protect me or the project.

Where are you located?  out of curiousity.


I completely agree, the wood always surprises you. I'm in Riviera, about a hour south of Corpus Christi
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Derik Mittag
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Re: Smooth Surface inside a Bowl
Reply #22 - May 6th, 2018 at 12:53pm
 
Here's a photo of some recent bowls I've done. They're not sanded, I just want to crank some out to try and get practice in on making them. All of them are mesquite.

Quite an improvement over the first photo I shared. Still have a slight problem eliminating the uneven spots with the gouge, but I smooth them out with a scraper. 
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David Hill
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Re: Smooth Surface inside a Bowl
Reply #23 - May 7th, 2018 at 5:45pm
 
Derik--I harvest and turn Mesquite all the time.  I wouldn't be all that concerned with the crack--especially if the tree had put matrix in it.  If not then some thin CA is just insurance.
On larger bowls if you're putting pressure on the wall with a tool, the wall will deform some, especially with thinner walls and you'll get chatter.  What helps is using sharp tools, light touch, and sometimes a bowl steady.
Couldn't see where you're located-might be fun if we were kind'a near. Oh haha--thought I had responded to you before--just need to read....d'oh---puts you about 3 hrs from me.
Mesquite is know for "ring shake" (circular cracks that follow growth rings)--because of the way it grows-that just tells you which parts not to use.  If it was bulldozed---be very picky of what you harvest, those cracks are unsafe.  Other than that, it's a very stable wood, doesn't make any difference if you turn it wet or dry.  Wet makes shavings, dry makes chips and dust, and it doesn't move like so many of the other woods.
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« Last Edit: May 7th, 2018 at 5:51pm by David Hill »  

Everyday liberating nice things from ordinary chunks of wood---and I like gnarly wood, the outcome is nearly always better than the start.
 
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John Grace
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Re: Smooth Surface inside a Bowl
Reply #24 - Jul 15th, 2018 at 9:41am
 
Derek...I just found this thread, read all of the comments, and studied the picture.  While I could very well be wrong, I think at least part of the problem lies with wood preparation.  The picture looks like it includes the pith which is that area of the wood almost assured to crack (and note where your crack emanates from?).  One of the nuisances if you will of prepping your own blanks is that you really need to commit yourself from a start to end perspective.  The clock starts ticking the moment the tree is sectioned into logs.  Recommend you find threads on proper blank preparation.  Cut the logs and then immediately cut them into proper blank orientation (i.e. avoiding the pith are by at least 1" if not 2"), and then immediately seal.  While not all woods crack equally, I know and prepare myself to spend several consecutive hours in cutting, prepping, sealing, and stacking the completed blanks with spacers for air movement.  Seeing as you're dealing with mesquite and are probably from the southwest, the air is exceptionally dry to begin with meaning your over-all prep time is on a serious stopwatch.  And in thinking of that, you may have better luck prepping your materials in whatever local season where you have the highest air moisture.  Just thoughts to consider...good luck.
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« Last Edit: Jul 15th, 2018 at 9:42am by John Grace »  

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Re: Smooth Surface inside a Bowl
Reply #25 - Jul 15th, 2018 at 5:45pm
 
One thing I haven't seen mentioned is to grind the heel off the bowl gouge - this can remove a lot of the tool marks in the bowl. Plus, it enables you to more easily engage the cutting edge in the interior of the bowl. Something similar to this picture at this Multimedia File Viewing and Clickable Links are available for Registered Members only!!  You need to Login or Register

I don't agree with increasing speed - I rarely turn above 1500 RPM which is the top speed on the low speed belt setting on by lathe.  If I am getting chatter, I try to see why and fix the problem.  Every once on a while, the chatter is partly caused by a combination of speed and other factors that create a harmonious effect - when this occurs, turning the speed down can be as effective as turning it up.
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Re: Smooth Surface inside a Bowl
Reply #26 - Aug 19th, 2018 at 12:30pm
 
Derik Mittag wrote on Feb 3rd, 2018 at 3:01pm:
As far as turning the wood with the crack, I have no problem with it, I'm comfortable with turning a blank like that. Yeah I know it can split and come at me, something I'm willing to risk. I'm going to use it as a inlay opportunity. Also, if I were to cut the blank smaller to get the crack out, it wouldn't be really worth turning. Most of my stock has cracks in it, it happens upon cutting the logs out of the tree so there's really no way to avoid it.


I agree with you here, one has to use their best judgement as to whether a piece of wood is sound enough to be turning. I like turning pieces with bark inclusions, and I have found through--hard--experience that a bark inclusion can be unexpectedly thin or weighty--so the difficulties that go with that are expected. 
Not to be disagreeing with anyone, but I never put a parting tool or with very rare exception a skew into the wood on a spinning bowl. If you are determined to turn a smoother surface, using a scraper is my go to tool of choice--specifically a large round nose scraper.
Honestly though, that doesn't look terrible to me--I would be inclined to try my 60 grit gouge on that surface, and then step through 80 and 100-120 grit--at that point you should be able to tell if you will be able to get the surface where you want it.

Best luck to you sir!
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« Last Edit: Aug 19th, 2018 at 12:31pm by Don C Davis »  
 
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David Hill
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Re: Smooth Surface inside a Bowl
Reply #27 - Aug 19th, 2018 at 4:59pm
 
Derik,
I process ALL of the wood I turn & I too turn mostly Mesquite-- and it is prone to cracks and ringshake.  Some of the cracks make it interesting to turn, giving inlay opps.  The bigger cracks I'll usually prefill with epoxy/inlay.  It's just the nature of Mesquite, It twists and turns with the wind--that gives the ringshake-- the small cracks that follow the growth rings--mostly toward the middle.  If they're "open" and I want to use that piece---well... that's what thin CA is for.  Since Mesquite rarely grows straight & with the twisting from the wind--the big cracks are more problematic.  If there's no "matrix"--where the tree has tried to mend it, then I'll generally try to avoid using that until I get epoxy into it.  If bulldozers were used, give serious thought to NOT using that wood--I just know that.
If I have doubts when turning then I'll use strapping tape or plastic wrap around the outside.  AND always wear PPE,  & stand out of the line of fire.
Don't be cavalier about wood flying apart--it hurts!!  I've been lucky and thankful for PPE.  At turning speeds even a small piece has lots of kinetic energy and really can seriously hurt or Kill ya.
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« Last Edit: Aug 19th, 2018 at 5:06pm by David Hill »  

Everyday liberating nice things from ordinary chunks of wood---and I like gnarly wood, the outcome is nearly always better than the start.
 
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Wil Russell
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Re: Smooth Surface inside a Bowl
Reply #28 - Aug 23rd, 2018 at 6:52am
 
Derik, It’s not easy sometimes to get a nice sweeping curve, especially with a gouge. I bought a large curved bowl scraper ground to a negative rake for the inside of bowls. They aren’t cheap but if you get a nice large one they’re quite stable and can give a good finish.

This is mine.

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Re: Smooth Surface inside a Bowl
Reply #29 - Aug 23rd, 2018 at 9:52am
 
I've starting using a large scraper  on the inside of bowls.  Doesn't leave tool mark rings.  Some woods  will have tear out.  I doing an oak bowl now  no tear out.  I finish up with a negative rake scraper before sanding.
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