• Congratulations to Rick Moreton, People's Choice in the July 2025 Turning Challenge (click here for details)
  • Congratulations to Jaramiah Severns for "Stacked Forms II" being selected as Turning of the Week for August 4, 2025 (click here for details)
  • Welcome new registering member. Your username must be your real First and Last name (for example: John Doe). "Screen names" and "handles" are not allowed and your registration will be deleted if you don't use your real name. Also, do not use all caps nor all lower case.

Twice turned bowls

R

robo hippy

Joined
Aug 14, 2007
Messages
6,268
Likes
3,472
Location
Eugene, OR
Well, this question keeps coming to mind, and 'if you want to know, then ask'. So, as a once turned bowl specialist, when I turn, I finish turn the outside, and then when I reverse the bowl, I am totally done with the outside. With some years of experience, my run out may be as much as 1/16 inch, and means plus/minus about 1/32 inch. So, for those who twice turn bowls, why don't you finish turn the outside when you form a new tenon? At worst, you may have to do a bit of shear scraping to true up the outside, and access to the outside of the bowl is much easier to do before you reverse it.

I have found that using a NRS or a very light shear scrape to finish my recess seems to be more accurate than a bevel rubbing cut with a gouge....

robo hippy
 
If I’m understanding your question, you’re suggesting that the out of roundness of a rough turned bowl would be minimal. On a 10” bowl it is not unusual for me to see 3/4” or so of difference between the diameter across the grain and with the grain after several months of drying . Having said that, I suspect I’m misunderstanding your question.
 
robo hippy said:
I have found that using a NRS or a very light shear scrape to finish my recess seems to be more accurate than a bevel rubbing cut with a gouge....
Click to expand...
???? What do you mean by recess??? The only recess I can think of on a bowl would be a dove tail recess for the purpose of mounting the the bowl using an expanding chuck.
 
robo hippy said:
for those who twice turn bowls, why don't you finish turn the outside when you form a new tenon?
Click to expand...
That is what I do. Many Others do the same
jamb chuck the dried bowl
line up the rim as close as I can get them.
true the rim - gets the bowl balanced.
turn the outside.
true the tenon Mount in the Chuck
turn the inside.
reverse Chuck turn off the tenon
 
I think I do what you are suggesting Robo. I use the flat plate with a gap in it that Gary has pictured in this thread: https://www.aawforum.org/community/threads/warped-bowl-turning.13098/. I true up the tenon and finish turn the outside, including sanding. Then I flip the bowl and finish cut the inside. Once sanded, I remove it from the chuck and vacuum chuck it to remove the tenon, and blend the bottom into the finished bottom of the bowl. Add any decorative elements to the bowl bottom, and done.
 
Me too. Jam chuck (probably better termed a friction chuck) the once-turned, now dry bowl between centers. Depending on the wood and other mystery factors, sometimes the bowl is mostly true, sometimes it is wildly oval. Whichever, I cut a new tenon and finish the entire outside (except the foot): true it up, make an initial pass at truing up the rim, finalize the shape, finish cuts, sand it.Then flip it around in the chuck and do the inside. Flip it again (usually in a vacuum chuck, or else friction chuck), remove the tenon and complete the foot. If not in a vacuum chuck, deal with the "nub" from the live center off-lathe. For each of these steps, I'm using whatever tool (gouge, scraper) is working for that piece.

When making a tenon, my personal preference (that works for me on most woods I turn) is to rough it out with my bowl gouge, then finalize the dovetail and tenon face with a spindle gouge. Some woods aren't happy with that, so I will try a scraper (OK, I admit, it's a skew).
 
Robo,
I twice turn most of the bowls I make.
When I go to re-turn the dried bowl, I just use my chuck as a jam on the drive side and run the tail stock into the mark I left when I roughed out the green wood. Center point.
First thing I do is true up the tenon. Then, I true up the outside of the bowl. Then I sand the outside of the bowl to 400 grit. Then I move on to mounting the 1/2 done bowl into the chuck and re-turn the inside of the bowl. Sand the inside to 400 grit. Then to get rid of the tenon, I use my vacuum chuck to hold the bowl so I can complete the bottom foot. I do use the tailstock to hold the bowl for almost the whole time I clean up the very bottom........then just the vacuum chuck to get rid of the stub and to sand. Bowl is done.
 
Hmm, maybe it is my memory. It has seemed to me, over the years, that most of the time when people do the twice turned bowls, they just true up the tenon, and then reverse the bowl and do all finish turning when the bowl is reversed. Apparently there are people that think like me.... Don't know if I will ever do twice turned bowls though.

As for the recess, that is my finished bottom and I don't turn it off. For years, I would use bevel rubbing cuts for the finish cut inside the recess. During my experimenting with NRSs in the last year or three, I started using them for the finish cut on the recess. I noticed a difference in accuracy when I reversed the bowl. Run out was reduced considerably. I have figured for years, that a bevel rubbing cut on bowls, no matter how light your touch is, will always leave a little run out. Most likely this is due to the end grain/side grain/uphill/down hill grain that you run into when turning bowls. The gouge just cuts differently going through the different grain orientations. With the NRS or a shear scrape, you nibble off the high spots and the run out is reduced. Don't think it is possible to get it perfectly true. This is only essential if you are turning in that 1/8 or less wall thickness on bowls, which I don't do.

Never really understood why people will sand the outside and inside of bowls at the different times rather than finish turning the entire bowl, except the bottom, and then sanding the whole thing in one go. I could possibly change that if I didn't use my sanding hood, which at present is not made so I can turn with it in place. I set up the hood and do nothing but sand, then remove it to turn more bowls. I need a more portable sanding hood. The good thing about it is that there is no need to wear a mask when using it....

robo hippy
 
I had best success on larger twice turned bowls by cutting small tenon into the inside of the bowl to fit the max extention of my chuck jaws, then flipping the bowl and using the chuck expanded into the tenon to securely hold to then turn , sand and finish the outside, put a recessed tenon and finish the bottom . Then flip again to turn , sand and finish the inside. Like Robo, I prefer to do once turned (turned thin) and let them warp.
 
I find it easier to sand the outside before hollowing out the inside of a bowl. It is true that this means that I can't really finish the bottom completely with a usable tenon still in place, but I have various ways of remounting the bowl with the bottom exposed to turn the tenon off and do a little sanding for a final finish on the bottom. I tend to use the same process when I cut a recess in the bottom.
 
Apparently I’m the odd one out with 2 turn bowls. I jamb chuck and recut the tenon, and cut off ~75% of the hi spots on the OD, then chuck the bowl and finish OD and ID. Using a slicing cut with an Ellsworth gouge its easy to get to the OD in the chuck. 2 reasons I do it this way 1) sometimes the chucked bowl doesnt run true, 2) I turn ~ 75% of the ID hi spots 1st to relieve tension, then finish the OD, then the ID. When I do a 2 turn I want concentricity.

For sanding, I leave tenons on all bowls after finish turning. Sometimes I sand right away, sometimes it may be months, and all in between. I prefer to chuck the bowl to hold for sanding, and do sand the whole thing at one time, and typically apply finish shortly thereafter. I tend to batch things - I may sand and finish 1/2 dozen bowls together.
 
I use a chuck face as my jam to true up the tenon....then I immediately mount it in the chuck, cut/shape it, sand it, and finish the entire bowl. This is fast and any other way seems like a waste of motion, as well as, this technique eliminates having to deal with runout aggravation.
 
hockenbery said:
That is what I do. Many Others do the same
jamb chuck the dried bowl
line up the rim as close as I can get them.
true the rim - gets the bowl balanced.
turn the outside.
true the tenon Mount in the Chuck
turn the inside.
reverse Chuck turn off the tenon
Click to expand...
Thats what I do. If there is a more efficient way, I would like to know...
 
My process is same as others - jam chuck, true up outside, clean up tenon, flip, turn inside, start sanding. As Dave says, it can really vary on how much work it takes. Some can warp so much there is barely enough material left to work with. Also may find a knot or crack that changes my plans. May take off more or less on inside or outside to balance where the defect ends up or if I can turn it away. Since I put sealer on the entire bowl I always second turn the entire bowl. Sometimes a little, sometimes a LOT but always the entire piece.
 
I seldom bother to jam chuck the roughouts - there's generally more than enough bite even on a warped tenon to use while turning a veryy shalllow recess inside the roughout. Then reverse the bowl using the recess inside, true up the tenon, finish outside form, sand and reverse to hollow. The bottom is finished using the vacuum chuck...
I am pretty scrupulous about balancing grain, so most warping is pretty symetrical.
 
Interesting discussion. I finish the outside first, but have always done it, tenon-outside-rim, thinking that my main goal is making a round tenon. Emiliano's comment about recutting the rim making for less vibration makes sense. I'm going to try it in reverse sequence and see if it reduces or eliminates the tendency for 'bounce' when cutting the upper part of the outside. Thanks for the tip.
 
This has been a great discussion - just starting to get back to some bowls I roughed out over the winter, and my approach has been different than what is outlined above, so I'll adjust and see how things go. FWIW, I've been friction chucking the blank, truing only the tenon, and maybe a little bit of the outside. Putting back into a chuck and truing the outside, then rim, then inside. I've struggled with the outside bottom third of the bowl with this approach, so I'm happy to try finishing the outside while in the jam chuck, and see if that works better for me.
 
Dean Center said:
recutting the rim making for less vibration makes sense. I
Click to expand...
Recutting the rim accomplishes two important things.
1. on a dry bowl with balanced grain the rim peaks and valleys are the most out of balance weight-wise part of the bowl.
cutting them true greatly reduces vibration. let’s you speed up the lathe
2. the cut rim gives your eye a clear target for finishing the curve on the outside of the bowl. You can clearly see the rim and meet it with minimal wood removal.

what I try to do is connect the foot to the rim with a pleasing curve.
if I got a good curve on the rough out - that curve is sill there just have to cut to it.
 
Kirk, getting from the bottom to the rim on a jam chuck can be tricky sometimes, and sometimes I can't get there. It's may be too far out of round and balance so the slightest bump in your cut can create a slight movement in the piece, which means all the work from bottom up is now out of round as well. If it gets to be an issue I'll clean up the tenon, add my foot then work up the bottom third or so, reverse and put in the chuck and then finish to the top. I don't use the tenon for a foot on my bowls so I can usually get from the top back to the foot without getting into the pucker zone of turning near my chuck. Sometimes not so it may take a bit of back and forth flipping to get the outside true and the shape I want. To Hockenberry's point, having a visual of the rim makes a huge difference for me. If I think the rim will need more work and will end up lower when done I'll either put a dark pencil line where the rim should end up or take my parting tool or cutter and make a groove for the visual of the final rim target. Without that I end up with a curve the doesn't match the intended final profile.
 
You must log in or register to reply here.
Back
Top