Sanding an out-of-round bowl........

[Odie]

I am currently working on a maple bowl that has warped badly during the seasoning process. The exterior has been brought to round, and sanded to 400grit. After bringing the exterior to round, it looked like it would make an interesting bowl if I did not true up the interior but left it in the shape it was after warp.

This presents a difficult task, because the interior has an extremely rough surface with tearout from when I roughed it out for seasoning. If I has known I was going to be sanding this surface after seasoning, I would have paid more attention to getting a cleaner cut, but that's water under the bridge now. 🙁

At a slow speed, about 100rpm, I managed to get a decent interior surface with 3" 50grit, and 3" 80grit discs......but, I'll tell you this was a very difficult thing to do with all the wobbling going on.....very hard on your arm.

I tried to do some of the sanding with the bowl not turning at all......and, I was unhappy with the results.....there was just too much digging in with the discs, not to mention that it was very difficult to control the sander without some rotation of the bowl.....the very slow speed produced better results!

I am now in the process of hand sanding with the lathe spinning at slow speed......am currently at 100grit. This is not easy, as all the wobbling is hard on my arm.

So far, I think I've got a winner in this bowl. The picture really doesn't do the looks of this bowl justice, as that out-of-round interior has real appeal........but, I don't look forward to doing the rest of the sanding! :mad:

I was just wondering if anyone has attempted anything like this......and, I would gladly accept some suggestions on how to sand this bowl without making my arm feel like it went through the clothes dryer! Ha,ha,ha! 😀

ooc

 

[Wayne Spence]

Sanding out of round bowl

I have had limited success using those flap sanders on a drill. I have had very good success using the Guinevere system which uses inflatable sanding heads and a flexible shaft-quite an expensive system. I bought mine for sculpture as well as turning.

Like you, using the lathe at a low speed takes forever to get into the low spots.

 

[Odie]

I have had limited success using those flap sanders on a drill. I have had very good success using the Guinevere system which uses inflatable sanding heads and a flexible shaft-quite an expensive system. I bought mine for sculpture as well as turning.

Like you, using the lathe at a low speed takes forever to get into the low spots.

I have gotten past the "low spots" with the coarse 3" discs......now, what I'm up against is a general oval shape to the interior. I suppose I could always sand by hand the entire inside, but I'm trying to figure out a way to do this without taking forever.......!

I was unaware of the Guinevere system, so looked it up.

I can see where something like that would be great on the sculptures to sand an uneven surface. How well would that work on a spinning lathe item? If the profile isn't too wild, then the inflatable backers would probably work out fairly well........but, I'm guessing.

Not sure about how well that would work for my particular application need, though......unless I wanted to sand the interior of the bowl without turning the lathe on.......????

I have a few of those flap sanders on hand, but haven't tried that.....yet! I'm going to give that a try, but when I get into grits above about 150, or so......looks like I'm back to using a folded piece of sandpaper in the hand.

Thank you for the suggestion.

ooc

 

[steelguy]

Sanding Out of Round interior

Odie - you might try one of these "sanding mops" on a flex shaft.

http://www.stockroomsupply.com/The_Sanding_Mop.php

Be careful!!

Jerry

 

[john lucas]

Odie I use 2" sanding discs. I use a home made index jig to lock the bowl in one position and then sand a little, move the index, sand some more.
Before that I used a method Bob Rosand sent in as a tip. Use a web clamp. Put it under the ways and over the chuck. Tighten it just enough to make things secure. You can then sand, rotate it buy hand albiet somewhat diffucultly, and then sand some more.
I have been wondering about building a sort of internal disc brake that I could lock with a lever outside the lathe. This would engage the disc whenever a lever was moved and would lock the spindle using a caliper similar to a disc brake on a bicycle. This would allow sanding or carving with the spindle locked and would be very easy to unlock. Of course I haven't taken the time to build it yet. Ideally I would like to position it inside the headstock.

 

[Odie]

Odie - you might try one of these "sanding mops" on a flex shaft.

http://www.stockroomsupply.com/The_Sanding_Mop.php

Be careful!!

Jerry

Jerry......outstanding!

I'll bet that would work. I've bookmarked that for future reference......just in case I ever decide to do more of these bowls.....and I very well may decide to do that! With the inside that doesn't match the outside like this......it has a handmade look, or some kind of different look that looks good, anyway.

thanks

ooc

Odie I use 2" sanding discs. I use a home made index jig to lock the bowl in one position and then sand a little, move the index, sand some more.
Before that I used a method Bob Rosand sent in as a tip. Use a web clamp. Put it under the ways and over the chuck. Tighten it just enough to make things secure. You can then sand, rotate it buy hand albiet somewhat diffucultly, and then sand some more.
I have been wondering about building a sort of internal disc brake that I could lock with a lever outside the lathe. This would engage the disc whenever a lever was moved and would lock the spindle using a caliper similar to a disc brake on a bicycle. This would allow sanding or carving with the spindle locked and would be very easy to unlock. Of course I haven't taken the time to build it yet. Ideally I would like to position it inside the headstock.

Hi John......

Man, I'm feeling pretty dumb right now! 😱 I never thought to lock the bowl by the index pin when I tried to disc sand without rotation. I'll have to try that again, too!

If this is something that you'd use a lot, that disc brake idea of yours sounds like a winner!

thanks

ooc

============================================

Now, I've got a couple of things to try.......hopefully, I can get out to the shop this afternoon to try them out......but, might not get to it for another day.

Thanks to all.......I really appreciate having this forum.....you don't know how many times it's helped me......and the solutions I was looking for usually turns out to be simple things I've overlooked! 😱

ooc

 

[Richard Baker]

I never thought to lock the bowl by the index pin when I tried to disc sand without rotation. I'll have to try that again, too!
ooc

I used to use the index pin a lot, but mine is threaded and screwing it in and out repeatedly gets old. Finally just sanded a dowel to a snug but not tight fit in the hole. The very end of the dowel is tapered, so that helps it find the next index hole.

 

[steelguy]

Sanding out of round bowl

Odie: I agree that the OOR center gives the bowl an appealing, hand made look. At least it was caused by green wood - I had bowls that looked like that, until I replaced a bent spindle!!!🙂

Jerry

 

[robo hippy]

Odie,

I do it all the time. I prefer warped bowls. The easiest way is to have a lathe with a minimum speed of 10 to 20 rpm. Your hand and the sander just won't stay on the wood above those speeds. Not a problem with my 3520A or my Robust. The 3520B has a minimum speed of 50 rpm which is too fast, and I would guess you have a Nova DVR. The 3 phase converters can be adjusted a bunch of ways, including minimum and maximum speeds. PM upped the minimum speed for some reason, and this was discussed here once before. WMH tool group won't let you lower the speed unless you send the headstock in, and they will void your motor guarantee. They say the motor will over heat, and you will burn up the motors electronics. I told them that I sanded out thousands of bowls that way and that the motor ran cooler than when I was turning, and they couldn't understand that, but insisted that the motor would over heat. Bull!

Anyway, you can hold the head of the drill in one hand, and let the drill spin the wood, using the other hand as a brake. Keep your drill arm close to your body so most of the drill weight is supported by your body, not just your hand. Do turn the drill speed down about half (I keep a piece of 1/4 inch cork under the trigger) and you won't dig in as much, and use light pressure. No need to press hard. I frequently do this anyway as with the slow speed, you can see scratches you may have left behind from the previous grits.

I have no idea about the flap sanders, but I wouldn't think they would be aggressive enough to remove serious tear out.

robo hippy

 

[Odie]

I used to use the index pin a lot, but mine is threaded and screwing it in and out repeatedly gets old. Finally just sanded a dowel to a snug but not tight fit in the hole. The very end of the dowel is tapered, so that helps it find the next index hole.

Tex.......

Yes, I could see how that would be a pita when repeated indexing. My Woodfast is a little simpler........index pin is external to the headstock and spring loaded.....very quick and precise. The indexing holes are on the main pulley, and internal to the headstock. It's a pretty good way of doing it.

later

ooc

Odie: I agree that the OOR center gives the bowl an appealing, hand made look. At least it was caused by green wood - I had bowls that looked like that, until I replaced a bent spindle!!!🙂

Jerry

Wow.....a bent spindle! I guess I could see how the inside might not match the outside if you re-chucked when switching!

Yes, I've had many many warped bowls before, but this is a new one for me......always brought both inside and outside to round.

ooc

Odie,

I do it all the time. I prefer warped bowls. The easiest way is to have a lathe with a minimum speed of 10 to 20 rpm. Your hand and the sander just won't stay on the wood above those speeds. Not a problem with my 3520A or my Robust. The 3520B has a minimum speed of 50 rpm which is too fast, and I would guess you have a Nova DVR. The 3 phase converters can be adjusted a bunch of ways, including minimum and maximum speeds. PM upped the minimum speed for some reason, and this was discussed here once before. WMH tool group won't let you lower the speed unless you send the headstock in, and they will void your motor guarantee. They say the motor will over heat, and you will burn up the motors electronics. I told them that I sanded out thousands of bowls that way and that the motor ran cooler than when I was turning, and they couldn't understand that, but insisted that the motor would over heat. Bull!

Anyway, you can hold the head of the drill in one hand, and let the drill spin the wood, using the other hand as a brake. Keep your drill arm close to your body so most of the drill weight is supported by your body, not just your hand. Do turn the drill speed down about half (I keep a piece of 1/4 inch cork under the trigger) and you won't dig in as much, and use light pressure. No need to press hard. I frequently do this anyway as with the slow speed, you can see scratches you may have left behind from the previous grits.

I have no idea about the flap sanders, but I wouldn't think they would be aggressive enough to remove serious tear out.

robo hippy

Well, ok.....thanks, Robo Hippy.......

That gives me something else to try. I can go slower. Will have to change pulleys again so the power is concentrated at the lowest speeds, but it's a "can do". I can go all the way down to 0 rpm, but to maintain any power I'll need to go to the first pulley setting.

Nope......got an original Australian Woodfast which I converted to variable speed. This is my third lathe, and have been using this one for the past 18yrs. now......I've been extremely happy with it.

ooc

 

[MichaelMouse]

Another benefit of the flex shaft sander. You can put the bowl in your lap if you like, holding with one hand and sanding as aggressively as you care to with the other. With the flex edge pads you can sand with quite a differential in diameter on the lathe without stubbing. http://i35.photobucket.com/albums/d160/GoodOnesGone/Flex-Edge-2.jpg

The sanding mops are not even as aggressive as their grit would cause you to assume, but, as they say on the Klingspor site, one to two grits finer. I have mine on one end of the "Big Buffer" pretty much constantly. It's for the spoons, but it will also do an excellent job on the warp-and-go green stuff that I don't wet sand but one grit. Their mini-mops are great detail sanders.

If you like the way this one looks, sand the inside of the next after roughing and just re-turn the outside.

 

[Odie]

Another benefit of the flex shaft sander. You can put the bowl in your lap if you like, holding with one hand and sanding as aggressively as you care to with the other. With the flex edge pads you can sand with quite a differential in diameter on the lathe without stubbing. http://i35.photobucket.com/albums/d160/GoodOnesGone/Flex-Edge-2.jpg

The sanding mops are not even as aggressive as their grit would cause you to assume, but, as they say on the Klingspor site, one to two grits finer. I have mine on one end of the "Big Buffer" pretty much constantly. It's for the spoons, but it will also do an excellent job on the warp-and-go green stuff that I don't wet sand but one grit. Their mini-mops are great detail sanders.

If you like the way this one looks, sand the inside of the next after roughing and just re-turn the outside.

Howdy MM......

I know that Ed Moulthrop really liked the flexible shaft sander. I'm not convinced that it will do any better for my purposes than what I have.......but, I don't have one (other than a Foredom).....so, I'll have to take your word for it.😀

Yes, I would have been much better off to leave a smoother interior surface at the roughing stage......but, I have yet to know beforehand just which bowls will warp this much, and which ones won't. If I knew for sure, that would make the "game plan" a lot easier to predict beforehand. It doesn't seem like there is a good formula for determining how much warp you'll get......species, moisture content, grain pattern......nothing seems to be a sure thing for determining how much it will eventually warp......and, for a bowl like this, the more the warp, the better! 😉

That's a good general question for the forum: Is there a sure-fire way to tell which roughed bowls will develop an extreme warp, and which will not?

Thanks for the input, MM......

ooc

 

[john lucas]

Odie I sand all natural edge bowls and square bowls with the lathe off using the indexing method. I can usually sand about 30 % from the middle out with the power on and the lathe running slow. Sometimes as much as 50 or 60 percent if it's a small bowl. When I get to the wings on anything larger than about 6" I sand with the lathe off. It's just quicker and easier and you don't accidentally sand the leading edge thinner.
It also gives me a chance to look really closely at areas that might have sanding marks from the last grit.

 

[Odie]

Odie I sand all natural edge bowls and square bowls with the lathe off using the indexing method. I can usually sand about 30 % from the middle out with the power on and the lathe running slow. Sometimes as much as 50 or 60 percent if it's a small bowl. When I get to the wings on anything larger than about 6" I sand with the lathe off. It's just quicker and easier and you don't accidentally sand the leading edge thinner.
It also gives me a chance to look really closely at areas that might have sanding marks from the last grit.

Thanks, John.....

It's my plan to use a little indexing when I can get back out to the shop.

Will try a powered very slow speed, too......about 10 rpm.

Also have some small flap sanders, but I don't think I have any grits over 150....regardless, will do some experimenting with them.


Thanks to all for the input......it's great that you guys (and gals, when applicable! 😀 ) give such great food for thought.

ooc

 

[MichaelMouse]

That's a good general question for the forum: Is there a sure-fire way to tell which roughed bowls will develop an extreme warp, and which will not?

Thanks for the input, MM......

Sure-fire? Not really, but the general rules shown here, which depend on orientation of the rings and their width is pretty reliable. http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.pdf Fig 3-3.

Some woods twist and reverse as they grow like elm and yellow birch, some grow fat on one side and thin on the other. Then there's "reaction wood," which defies all logic in the way it decides to move. Note the relative drop on the right, where rings are closer compared to the left, even though it obeys the general rule of crown toward center.

 

[robo hippy]

I have figured that water content has a lot to do with it. Pacific Madrone is one example. You can not use the 10% rule with it. I have had 13 inch bowls end up 13 by 9 inch footballs. Madrone is some thing like 90% water content when harvested. The bowl blanks will sink in my soap solution. Most other woods are around 60% to 65% (I got this out of Fine Woodworking). More water to lose equals more shrinkage. I have seen Sycamore do this as well. Spring harvested trees seem to move more than fall/winter harvested trees, and dead standing trees seem to move less as well. This uncertainty is one of the reasons why I like the warped bowls.

robo hippy

 

[Odie]

Thanks for the link, MM.......but, unfortunately I can't run a pdf format. Acrobat is up to date, but something wrong in my computer.

I'll have to agree that there are things to look for when predicting how much warp will occur.....but, it's not as reliable as we would like it to be.

ooc

========================================

I was out in the shop for awhile, and this is what I found:

With the belt on the slowest speed pulleys, I didn't have to use the index pin. I was able to sand at 0 rpm without the index pin because the speed ratio caused anough drag through the motor to stiffen the spindle just the right amount.

The flap wheels I have didn't impress me. If their profile shape more matched the bowl shape, they would work better, but changing their shape to suit one purpose at hand isn't really worth the effort to do so, unless it's a last resort. I've seen those 6" diameter (?) with about 6 flaps supported by brush affairs........that may work better than the multi flap sanders I have........

I was able to make progress in the sanding of this bowl by using a combination of zero rpm sanding and speeds from about 25 rpm up to about 100 rpm.

Things look good and I'll be able to do another of these out of round bowls again......should I choose to do so. That's questionable, but if I run across the perfect candidate, I may go for it!

ooc

 

[MichaelMouse]

I have figured that water content has a lot to do with it. Pacific Madrone is one example. You can not use the 10% rule with it. I have had 13 inch bowls end up 13 by 9 inch footballs. Madrone is some thing like 90% water content when harvested. The bowl blanks will sink in my soap solution. Most other woods are around 60% to 65% (I got this out of Fine Woodworking). More water to lose equals more shrinkage. I have seen Sycamore do this as well. Spring harvested trees seem to move more than fall/winter harvested trees, and dead standing trees seem to move less as well. This uncertainty is one of the reasons why I like the warped bowls.

robo hippy

Sort of puts you at odds with the wood technologists who experimentally determined and maintain that the wood does not shrink until it goes below the fiber saturation point of ~30% moisture content. Plus or minus a couple % for extractives, seems a good figure for nearly all wood, madrone included.

Some of your common woods with more moisture content than your 65% by dry weight in the sapwood include almost all the common conifers, lead by western red cedar. Hardwoods (HAH!) in the willow/cottonwood/poplar family are also very damp.

 

[Bob Hadley]

I ended up using a cabinetmaker's curved scraper on the various "elipti-bowls" that I made in 2007. This saved tons of sanding and, I think, more accurately preserved the natural shape that resulted from drying. After scraping I hand sanded with 180/220/360. The final polish was with a power drill driving a scotch-brite pad backed with some carpet padding.

I think some woods may be better suited than others for this result. Poplar and Sycamore have worked well for me. Walnut and elm and eucalyptus... not so good.

It pays in the end if, when prepping the roughed-out bowl to put the nicest shearing cut you can on the final inside pass -- obviously it saves lots of sanding/scraping later. Most of the clean-up is just to remove whatever tint might be left from the wax or Anchor Seal you've used to prevent cracking.

This is just one example...
http://http://www.aawforum.org/photopost/showphoto.php?photo=4402&size=big&cat=&ppuser=218


Come to think of it, I use a hand scrapers instead of sanding whenever I can. I heard about it somewhere... maybe at the Symposium in Portland.

 

[hockenbery]

like Odie said in the beginning the finished surface begins with the tool finish.


As to what to do next time....
I have been using The Abralon discs on wet wood and they work quite well and cut the wet fibers rather than bending them over.
You could sand on the lathe with Abralon then dry the bowl and touch it up with 320.

Best of all, If you can get a good tool finish you don't have to sand a utilitarian bowl.
Mike Mahoney gave a terrific demo on Heirloom bowls and he doesn't sand the bowls he uses in his home.

happy turning,
Al

 

[Vaughn]

Sort of puts you at odds with the wood technologists who experimentally determined and maintain that the wood does not shrink until it goes below the fiber saturation point of ~30% moisture content...

To paraphrase what we used to say in the construction management business...sometimes you have to shoot the engineers and just build the dang thing.

Enjoy your laboratory. Me, I'll be out in the shop turning something.