Re-turning - best strategy?

[Prashun Patel]

I turn mostly green bowls. Typically, I turn an oversized tenon on the rough out. After drying, I use a jam chuck and true up the tenon.

When not re-turning like this, I prefer to use a recess.

What is the best method you've found for holding a roughout without the tail stock so that I could true up a recess after drying?

Vaccuum chuck?
Longworth?

I'm not a fan of Cole jaws (too long to set up) or a Donut chuck (too hard to center).

If it matters, I'm using a Laguna Revo 18/36. Their vaccuum chuck is about as much the longworth.

[Jim Tobias]

Prashun,
I'm still in the novice area as a turner (5 yrs or so), but I recently purchased the Vacuum Chuck system (ALAREVO18 VACUUM) and the Holdfast vacuum chucks. I have to say my stress level is so much lower than when trying to center things on a jam chuck or setting up a Longworth. There is an adaptor for the tailstock ( Nova , I believe) that allows you to turn it around straight off the headstock and have it centered perfectly before turning on the vacuum.
Now, I don't do many wet turned bowls so I cannot speak directly to that process. But even for everyday turning situations, the vacuum chuck saves a lot of headaches.
Jim

[Paul Williams]

I have a vacuum chuck and a longworth, but unless there is something different or special about the rough out, I tend to use a jam chuck for ease of centering, and virtually no set up. I always leave a center mark in the tendon. I have a piece of wood with a non-slip pad attached to one face. I chuck that up. Hold the bowl with the center marked tendon against the 60 degree live center and advance the tail stock until the roughout is against the non-slip pad. Then gently remove wood to make the tendon round again. I do basically the same thing when I have a recess.

[Prashun Patel]

Thanks Guys. Paul, I do as you do. But I want to turn a recess not a tenon. I can’t do that with a tail stock so I don’t believe a jam chuck would work.

[David Walser]

... I want to turn a recess not a tenon. I can’t do that with a tail stock so I don’t believe a jam chuck would work.

You can turn a recess with the tailstock in place. Just turn the recess, leaving a small nub where the live center makes contact with the bowl. After the recess is turned, you can either leave the nubbin on (it should fit between the jaws of your chuck) or remove it with a knife or chisel.

[Prashun Patel]

Sorry if I am not being clear. When re-turning the dried bowl, truing up the recess is really difficult with the tail stock engaged. The recess is dovetailed. I have to come in with my dovetailed scraper parallel to the ways. The tailstock is therefore in the way.

How would one true up the recess with the tailstock engaged?

[Edward Weber]

Longwoth chucks are pretty useless, unless the piece is concentric. Vacuum chucks need a relatively flat surface the form a seal. When second turning, the bowl blank typically won't have these features.
To form a new recess, tenon or foot without the tailstock, a donut chuck or cole jaws are probably your best bet. I know that's not the answer you wanted but you need to hold a warped, rough bowl on the headstock securely enough to true up the foot, your choices are limited to a degree.
JMO

[Brice Rogers]

Some thoughts:

1. I made a special tool that allows me to get in and re-turn the recess with the tailstock in place. The tool is a 1/2 " square bar with a small cutter mounted at roughly a 90 degree angle. The cutter was made from a file and ground so that it gives me the correct angle dovetail. I've seen other people take a skew (etc.) and remove the original front and put a "hook" of sorts in the side. Also, I made a 1-1/2 or 2" tip for my tailstock live center that allows the body of the tailstock to be back from the tenon/mortise.
2. Before I had a vacuum chuck, I had made a set of wooden faceplates. To true up the tenon or mortise, I would sometimes hot glue the bowl to the faceplate. As long as I didn't get crazy-aggressive, that would give me great access w/o a tailstock in place.

[Kevin Jenness]

As Brice said, you can reshape a scraper to reach the recess with the tailstock engaged. Vacuum chucks won't work on a warped piece unless you have a super thick and squishy gasket.

I am assuming that you are talking about re-turning a previously turned and dried blank. If you want to turn a recess in the foot of a dry unshaped piece you can start with a screw chuck or a drilled recess in the inside face

[John K Jordan]

I don’t know about “best strategy” but I made a tool that allows cutting or cleaning up a recess with support from the tail stock. I ground it from some kind of old HSS tool with a rectangular shaft, a scraper I think. I’ve used it to re-turn warped recesses on roughed-out bowls supported by the tailstock and driven by some type of jamming at the headstock. I think one nice thing about using headstock jamming and tailstock support is it makes it easy to make small adjustments to align both the top and bottom of the piece as needed.

If the recess is large, it will clear a std Oneway style tailstock. If small, I make a tailstock extension from wood, usually to fit into a Nova live center but also have made an extension threaded to fit the Oneway center and turned down enough to provide clearance.

I shaped this tool and sharpen it using CBN wheels with square (instead of radiused) edges, with grit down the side (which I often find useful). I’m don’t have access to the photos on my computer right now but here a couple I have in one of my albums here.

https://sawmillcreek.org/attachment.php?attachmentid=453101&d=1614360691

https://sawmillcreek.org/attachment.php?attachmentid=453100&d=1614360691

As shown in the second photo, this tool is also useful for cutting a recess into a dry bowl or platter blank with parallel top and bottom, jammed with the tailstock, usually against some widely opened jaws of a chuck in the headstock. In this case the recess I make is a narrow ring, just wide enough for the chuck jaws. I don’t have a diagram with the tool and wood blank in the best orientation for visualization - I should draw one showing the tailstock in place as well to show how much clearance there actually is for my 50mm Nova jaws. It may not be obvious in the photo but the inside angle of the tip is a little less than 90-deg to allow cutting a slight dovetail in the recess while keeping the bottom flat.

BTW, I collect old tools, buying cheap or freebees, to give to students and to grind into special shapes - quite useful at times!

JKJ


I turn mostly green bowls. Typically, I turn an oversized tenon on the rough out. After drying, I use a jam chuck and true up the tenon.

When not re-turning like this, I prefer to use a recess.

What is the best method you've found for holding a roughout without the tail stock so that I could true up a recess after drying?

Vaccuum chuck?
Longworth?

I'm not a fan of Cole jaws (too long to set up) or a Donut chuck (too hard to center).

If it matters, I'm using a Laguna Revo 18/36. Their vaccuum chuck is about as much the longworth.

[Paul Williams]

A bedan tool sneaks by my tail stock. Then if I want to add a dovetail I use a NOVA dovetail recess tool held at a bit of an angle to clear the tail stock. I have also used a pen saver live center which is quite thin when I needed more room. It really doesn't take much if all you need to do is round out an existing recess that has become an oval.

[Prashun Patel]

"If the recess is large, it will clear a std Oneway style tailstock"

Thanks for the awesome feedback guys. John, I realized that the key is just turning a larger recess such that it clears the tailstock. I'm going to make such a hook/recess tool for smaller recesses.

Thank you Everyone.

[Jeffrey J Smith]

I'm a fan of simple solutions; I turn a fair number of bowls and always setup to return dried roughouts the same way. I rough everything with a chuck using number 3 dovetail jaws - Oneway or Vicmark (about 3-3/4" dia). The tenon is usually close to 4"; the same chuck/jaws are typically used for both turnings. When dry, the tenon has generally warped, but not so much that it can't be safely held in the jaws. I chuck the tenon, then turn a very shallow recess in the inside of the bowl (seldom no more than 1/8" deep) at a point that lets me simply reverse the bowl and true the tenon when the outside is finished. Turn it again and hold by the trued tenon to finish the inside. It gets turned once more and held with a vac chuck to finish the bottom.
The whole process takes longer to explain than to do and the hold is very secure. I do keep the speed down when turning the recess on the inside while holding by the warped tenon, but the jaws have never lost their grip...
Even though I always use a tenon rather than a recess, the process should work for either.

[Peter Blair]

I just made my own scraper with an adjustable offset handle that I use for truing up both recess' and tenons.

[Mick Fagan]

Quite often with green bowl blanks that have been drying and distorting, I make a recess cut in the inner of the bowl and then switch chucks for a wide set of jaws on my VM100 or VM120 chucks then reverse the bowl onto the correct set of jaws using expansion to hold. I am then able to completely do the outside of the bowl to finish.

Richard Raffan shows how he uses this method, which is simple as anything and quick. Start at 4:45 for where he uses this method.

https://www.youtube.com/watch?v=Lp8L4NR1Jcc

Mick.

[Paul Heely]

Edit: Just read Mike's post above, which basically says the same thing as I say below.....

if you have large enough jaws you might try turning a recess on the inside of the bowl to hold it while you true up the recess on the bottom of the bowl. I saw Ashely Harwood do something similar in her bowl turning video. The process would look something like this:
1. Use the existing out of round recess and the tailstock to mount the bowl with the foot of the bowl at the headstock end of the lathe. Basically a jam chuck using the chuck inside the untrue recess.
2. Turn a recess on the inside of the bowl.
3. Reverse the bowl and hold it on the recess you just turned on the inside of the bowl. True up the recess on the foot of the bowl.

I've done this many times when I was messing around with the push cut cut stuff, and it works well to hold the bowl. Only catch is it requires a good size set of jaws to hold the bowl by a recess on the inside. I'm lucky enough to have a full set of dovetail jaws for my VM120 chucks.

Paul

[Neil Strong]

I put a recess in the inside bottom of bowls at the green turning stage. I have sets of spring dividers that are set to the diameters that will shrink to the sizes of my long nosed jaw sets (2", 4" & 5") when seasoned.

I make a slightly deeper internal recess in woods that have larger radial to axial shrinkage to ensure I get four contact points when I re-chuck.

For very deep bowls I use a 4" or 6" extension adaptor to position the chuck and rim of the bowl further away from the headstock.

Final turning step 1: I complete the turning of the outside of the bowl with a recessed in the foot that is proportional to the size of the bowl and then complete by polishing the outside of the bowl.

Final turning step 2: I remount using the outside bottom foot recess to turn the inside of the bowl and then polish.

Bowl done!

Some like to go back and turn off the outside bottom of their bowl. I like the bottom of my bowls to have a well defined foot, which I complete with Final turning step 1.

I turn all of my bowls outboard and never use the tailstock (unless spindle turning).

As seen in the above video link, RR prefers to clamp onto the foot of his bowls when doing the final turning of the insides, for which he mostly uses multi-step jaws but not in that video. I prefer to hold by expanding into the completed recess in the foot.

One of the disadvantages of my method is that I need to have many jaw sizes (and dedicated chucks :~) to get the right proportions to match the different bowl sizes, whereas Richard only needs the multi-step jaws and one chuck for that.

On the survival rate of these two holding methods, RR's is better but I have seen him lose a few off the chuck! I probably lose a few more due to the occasional inside cut that is too heavy, which can pull the piece out of the recess. But that doesn't happen very often and I've lost count (somewhere after the first thousand) of how many bowls I've successfully made that way.

Worth a try if you haven't already.