I was watching a demonstration by Matt Monaco and, after he turned the outside of a bowl and then re-chucked it at the foot, he re-trued the outside of the bowl with left-handed and downhill cuts with a bowl gouge and then shear scraped to clean up tear out before finishing the inside. I hadn't seen that technique before so I gave it a try. It is nice to have the outside of the bowl running perfectly true while finishing the inside. It seems to allow higher rpms, so faster turning and smoother cuts. However, it is awkward to turn the outside of a bowl mounted that way. It also creates a mismatched area near the foot that must be blended in later. Just wondering if others use the technique habitually and have any thoughts on it.
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Re-truing the outside of a bowl after re-chucking at the foot
- Thread starter Holmes Anderson
- Start date
If a tenon is properly made there “shouldn’t” be runout when flipped, but I’ve had it happen enough that I don’t finish the OD until the tenon is in the chuck. There should not be any mismatch at the foot if the tenon is properly made and seated.
If runout is significant, I’ll use a push cut to start rounding. That is followed with a pull cut using the right wing of a long wing bowl gouge, handle dropped, for a shear cut. Ellsworth called this a slicing cut.
Finish it off with shear scraping with a long wing gouge or a scraper.
If runout is significant, I’ll use a push cut to start rounding. That is followed with a pull cut using the right wing of a long wing bowl gouge, handle dropped, for a shear cut. Ellsworth called this a slicing cut.
Finish it off with shear scraping with a long wing gouge or a scraper.
One of Tomislav's videos, he mounts the dry blank from the tenon and centers it before tightening it down. He turns a recess in the bottom and then retrues the tenon, then reverses to turn the inside and outside. Can't remember which video it was though. The chuck he used for the recess on the inside had huge jaws, like at least 6 inch, maybe 10 inch. I only once turn my bowls. Some do turn most of the outside when the tenon is facing the tailstock. A bit easier access. I did one and used my BOB tools to turn the bottom from the tenon side, then once there was clearance, I used the 40/40. With my recess that I use on my once turned bowls, I do like a NRS for forming the inside. I would probably use a skew for a tenon. The idea is that the NRS will nibble off the "high" spots till the surface is dead flat. Other than that, if there is a 1/16 inch wobble, that means plus/minus 1/32 inch which is pretty close. Since I started using the NRS for the insides of my recesses, I generally get way less than that.
robo hippy
robo hippy
I was taught that there is always a little runout when you take the blank out of the chuck and put it back on. The wood fiber can deflect or compress and you won’t be on the exact same center. No problem rechucking metal, always on wood.
Thread is about runout when flipping the bowl and mounting by the tenon after creating the tenon on the TS side.
As for remounting a tenon, I mark all my tenons from a mark on the chuck to be able to rechuck without runout. I tend to get jaws pretty tight, and retighten after a few minutes - crushes the fibers pretty well. Works most of the time, there’s always the exception.
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Lots of ways to get good results.
What I do with NE bowls is make the outside finish cut with a pull cut foot to rim after I have done some hollowing to allow tension movement. Then turn the wall to thickness and finish the hollowing
With a 2nd turn of a dried bowl I friction turn the bowl against a chuck with partly opened jaws.
Center it well, true the rim, finish turn the outside, true the tenon. Mount in the chuck.
vast majority run quite true. If i don’t get it running true i true the outside with a pull cut then finish turn the rim and hollow.
Pull cut. Tiny shavings a smooth surface
Shear scrape. Tinier angel hair shavings smoother surface
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The last few minutes of this video
View: https://youtu.be/vS0mIefN4kU?si=gyMPKNRveUm_GYMm
and first few minutes of this video
View: https://youtu.be/COyNLnbrvao?si=zkPp9YdWsT0E5B22
show what I'm talking about just to be clear.
Maybe "run true" is subjective. In the first video he suggests that the runout is caused by the alignment of a serration on the jaws with the edge of the tenon and that with care in mounting the runout can be limited to the point that the outside of the bowl can be re-trued by shear scraping alone, so maybe that would be runout on the order of 1/16", 1/32" or maybe only 1/64". Some might consider that amount of runout in a wood bowl as running true. It can certainly be worse and can easily be seen in some of the videos of seasoned turners such as Richard Raffen who obviously lives with it because he puts finish on the outside before final turning the inside. That small runout is not noticeable in the finished bowl and is negligible relative to seasonal wood movement but Monaco says it makes a difference in surface quality on the inside of the bowl by eliminating a source of vibration. It sounds like at least some of you only re-true the outside if the runout is exceptionally bad, which seems sensible to me.
and first few minutes of this video
show what I'm talking about just to be clear.
Maybe "run true" is subjective. In the first video he suggests that the runout is caused by the alignment of a serration on the jaws with the edge of the tenon and that with care in mounting the runout can be limited to the point that the outside of the bowl can be re-trued by shear scraping alone, so maybe that would be runout on the order of 1/16", 1/32" or maybe only 1/64". Some might consider that amount of runout in a wood bowl as running true. It can certainly be worse and can easily be seen in some of the videos of seasoned turners such as Richard Raffen who obviously lives with it because he puts finish on the outside before final turning the inside. That small runout is not noticeable in the finished bowl and is negligible relative to seasonal wood movement but Monaco says it makes a difference in surface quality on the inside of the bowl by eliminating a source of vibration. It sounds like at least some of you only re-true the outside if the runout is exceptionally bad, which seems sensible to me.
That’s fine, but what I am saying is that once a blank of wood is removed from a chuck, not matter what the rest of the story is, the bowl will have run out when it’s clamped in any sort of way again. And since name dropping is counting in this post, it was a class with John Jordan, at his shop, where I learned that.
Well, my experience does not agree with your statement that a re-chucked bowl will always have runout, regardless whose name is dropped. Or....perhaps 0.0001" on a wood bowl counts as runout?
I've seen lots of demos by expert turners and truing up a blank after changing the mounting is extremely common. (cf Richard Raffan's back hollowing video from about 3 years ago, referenced in another current thread)
If you make thinner walled bowls or natural edge bowls, the untrue blank can show up as an obvious difference in width of the rim around the bowl and could possibly ruin an otherwise excellent piece. Boxes can also show the offset between top and bottom. DAMHIK
If you make thinner walled bowls or natural edge bowls, the untrue blank can show up as an obvious difference in width of the rim around the bowl and could possibly ruin an otherwise excellent piece. Boxes can also show the offset between top and bottom. DAMHIK
(oops, wrote this then noticed I forgot to click “Post reply” before heading out of state. I haven’t had time to read all the posts yet so some of this might have been covered. Edited a bit after a good night’s sleep. JKJ)
Holmes,
A bit of extra information might be helpful to narrow assumptions that don’t apply:
- was this bowl from green wood or dry wood?
- Rough turned then dried?
- Face grain or end grain?
I expect runout with wet wood but even dry wood will often have “some” run out when re-chucking a tenon, since the wood fibers will be crushed a bit the first time. I’ve gradually learned what works better for me.
Besides what I think is the most important - green vs dry - some related variables I can think of are:
- the grain orientation,
- species, hardness,
- how mounted,
- how tight the chuck key is cranked, and
- whether the tenon is mounted exactly as it was the first time - and in the same position.
I found the run-out (and the resulting mismatch at the base) can be decreased if the tenon is made just barely larger than the closed jaws so the sharp edges of the jaws aren't biting deeply into the wood, if excessive tightening avoided, and especially if the jaws are realigned so they bite into the same indentations made the first time. Before removing a piece from a chuck, I like to make a reference dot on the wood in the gap between jaw#1 and jaw#4. That way I can quickly remount the tenon exactly in (or very close to) the same indentations in the tenon. Necessary, as always, is a good flat on the base for the faces of the jaws to bear against.
I always re-turn the outside after re-chucking if there is any “significant” runout. If the cuts are awkward, a few light practice passes might help. If the runout is very minor, a pass or two with a curved NRS might be enough.
BTW, the variability of re-chucking a tenon is one reason I've mostly gone to starting with a screw chuck in what will be the top of the bowl (starting with a dry solid blank), turning a careful recess in what will be the bottom (just a hair larger than the closed jaw diameter), complete the foot and the outside (even smoothing and finishing), then reverse and hold by the recess to shape, smooth, and finish the inside. This completely avoids re-chucking. I do usually use a tenon on a twice-turned bowl since truing up a warped tenon is a bit easer than a warped recess.
Of course, starting with dry wood blanks makes all this SO much easier. Any warping then is probably due to internal stresses relieved or humidity changes since last mounted. Again, this is my personal experience, mostly learned from mistakes!
JKJ
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I always make my tenon as soon as I get the bowl to a point that I'm able to make the tenon then finish the outside of the bowl. Then I would turn it and put tenon in jaws. Always there was visible runout. What I started to do was after putting on the tenon and then finishing the outside I would then make a cleanup cut on the tenon before turning it around. This made the runout a lot smaller. I doubt that any bowl ever made runs true between the inside and outside. Removing wood allows stresses to move in the wood. That last cut on the tenon has made it better for me.
I use recesses instead of tenons and don’t experience run-out when turning a bowl around.
Tim
Tim
Russ Braun
TOTW Team
I took a day long class with Matt; his tool skills are off the chart. My attempts to mimic what he does were challenging at best! I would leave it at that, haha! Now I’m not a big fan of a foot on a bowl but for some reason, feet are OK…this just means after getting the outside just right, there’s way more exterior work to do off the lathe!
It’s amazing how much stress can be in a blank. I wrote about this before: I once put a long dry hard maple blank on the lathe and turned the outside and base of a small dished platter. Walked across the room for something and heard a loud CRACK! Removing some wood from the outside relieved enough stress to require a design change!
I remember when just starting turning a Raffan wrote some advice on turning even quite dry roughed boxs: turn both pieces to ALMOST the finished size then let the box sit in the chuck for at least overnight for stress relief before finish turning. This sometimes made the final fitting easier!
(Good reason to have extra chucks too!
)JKJ
Mike Jackofsky taught me to re-true after turning the piece around. Sometimes it’s just a couple shear cuts, sometimes more. I like Bill’s idea and will try that—final cuts in tenon before flipping. Great thread!
The mismatch is created by the impracticality of reaching the entire bottom 1/3rd of the outside for re-truing because of bowl shape and proximity to the chuck jaws. Monaco talks about it in the video and suggests blending that bottom 1/3rd area into the re-trued side when reversing again to finish the foot (if the bottom 1/3rd can't be reached with the bowl mounted by the tenon, but in the video it can be reached).
It looked like a dry blank to me but I don't know for sure. Certainly a cross grain bowl.
Marking the bowl to indicate tenon position relative to the chuck jaws is good advice. I noticed in Raffan's videos that he does that too. In the Monaco video he aligns the grain with the gap and makes a pencil mark. That alignment marking and Bill Blasic's advice about tweaking the tenon just before reversing are gems. It's the little things that make a difference.
I’ve processed many 100s of turning blanks from green logs for drying and tested and dried a lot of unknown wood. If you haven’t tried it: the easiest way to know if the wood is completely dry takes a bit of time but works well: I put a piece of tape on the wood and weigh it and record the date and weight in grams. Periodically (maybe every month or two) I reweigh. When the weight quits dropping, or even goes up with the seasonal humidity changes, I mark that piece dry. (My shop has central heat and air which keeps things fairly constant so that helps a lot!)
I do have two types of moisture meters (pin and pinless) but the weight method is more reliable for several reasons!
One reason I love this forum is advice from others on nearly any topic - sometimes just the perspective difference provides a gem.
JKJ
That’s where I go to hand scrapers, often off the lathe.
With good scrapers and some practice it’s surprisingly quick. My usual way for most things these days is: turn, NRS, remove from lathe and uses hand scrapers, sand by hand, finish. Often after scraping sometimes all the sanding needed is 600 grit or 400.