Finishing Bowl Bottoms

[Steven Park]

For a while now i've been using cole jaws to finish the bottoms of my bows. But for the bigger bowls that are 17"+ its harder using the cole jaws. What are some ideas for finishing the bottom of bowls you might have?

[Prashun Patel]

I don't have a vaccuum chuck, so I take the bowl off the lathe when I have finished all but the center 3/8" of the bottom. I do that part on the bench: I cut if mainly flush, then use a router plane to flatten, and finally sand and finish on the bench.

[David M Peters]

Have you tried building an extra-large Donut Chuck?

[Robert Hayward]

I use a piece of construction grade SYP 2X12 and a face plate. I laminate two or more pieces cross grain style to get whatever diameter I need. Then make a jam chuck out of the assembly. Google wood lathe jam chuck or similar and you will get bunches of leads.

[Thomas Canfield]

A loose fitting jam chuck/piece of scrap wood shaped to fit a ring of contact at about 1/3 or more of diameter of piece and a piece of rubber shelf liner, leather, or other soft pad will drive the piece with pressure of the live center in tailstock. You can then turn and finish the majority of the bottom leaving a small nub (diameter determined by quality of wood) that should be cut off with flush cut saw with protective material against bottom or chisel. Breaking off the nub can result in tearing out the bottom. Also care should be given to the pressure on the tailstock with a thin bottom.

That is the reason to always leave a center point in the bottom to align for remounting. This jam method works for all sizes and even natural edge pieces. A modification of method with longer jam piece can be used on hollow forms when support of top.

This jam method works vacuum will not work due to worm holes, bark will not fit cole jaws, out of round will not fit a donut chuck, ..............

[John K Jordan]

For a while now i've been using cole jaws to finish the bottoms of my bows. But for the bigger bowls that are 17"+ its harder using the cole jaws. What are some ideas for finishing the bottom of bowls you might have?

Steven,

One way I sometimes use is to not reverse it to finish. I turn the bottom first with a recess for the chuck, add some detail on the bottom, then reverse to turn the inside/top and forget about the bottom. Here are some done this way:

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I've tried lots of other variations and some I like more than these but I haven't photographed them yet. I started using this technique on these small squarish platters since I couldn't easily hold them with the Cole jaws (and the first one I made had a hole so the vacuum chuck wouldn't work!)

I did this platter basically the same way - the recess is the circle inside the triangles in the base. (Frank Penta's teaching.) This held fine for a platter but I wouldn't trust it with a heavy bowl.

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JKJ

[Brice Rogers]

I went to Home Despot ;) and bought a circle of wood about 20" in diameter and perhaps 1-1/4" thick. I glued on a threaded glue block but could have also attached to a faceplate and made it concentric. Then I made a bunch of round pencil lines on it to help centering. When I want to work on the bottom of a bowl to finish the foot, I use my tailstock to apply pressure to the bottom of the bowl. I tap the bowl this way and that way until it is perfectly centered. It isn't that difficult to get the bottom centered to within perhaps 0.005" or to the concentricity of the foot. When it is good enough, then I hot melt glue 1x1"x3/4 blocks around the perimeter on the big disk (but not on the work piece at this point). That guarantees that it remains centered and is not going to shift. At this point I can work on the bottom IF I leave the tailstock in place. If I want, I can add a number of screw on wedges to hold the piece in place. Sometimes I add stretch wrap. Sometimes I add filament tape and sometimes I add some hot melt glue. But I have never had one come loose. However, I take light cuts and only work on the foot.

[Leo Van Der Loo]

I have made extensions for my Oneway Mega Jumbo jaws, so up to 17” I can hold with it, larger than that and I use something similar to Brice, but as I don’t have a tailstock on the outboard of my large lathe, I will measure the outside dimension of the bowl and turn a very shallow recess, I hate to have the bottom show how the piece was held in on the lathe, it’s just not finished IMO.

Small blocks are then screwed onto the pine wood boards, (they are screwed onto a large plywood disk and can be changed for new ones or flipped over) and those hold the piece solidly.

This is a 28 inch Maple bowl held on a large disk.
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A Bowl this size I can hold with my Oneway Mega Jumbo jaws.

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Needed the Oneway Mega Jumbo jaws extensions for this one.

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[Richard Dooling]

I like this Leo. Very straight forward. I have found Doc Green's "Fixtures and Chucks" to be a helpful resource.

[Thomas Wilson80]

Interesting idea Leo - I would have thought that those wood braces would either scratch or indent the bowl, but from the finished pictures that is clearly not the case. Might have to try that!

[John Keeton]

I finish everything but platters the same way - by reversing the bowl with light tailstock pressure against one of my two Holdfast vacuum chucks as a cushion. I finish the bottom with a slightly concave surface, texture a small border and pare down the tenon to a 1/4" post. I then remove the piece, slice off the post with a wide sweep carving gouge and sand the remnants of the nub with a sanding disc on my Jacobs chuck held in the spindle. About a 5 minute task. The result is clean and ready for signature and finish.

I started out with donut chucks and cole jaws, but abandoned all of those methods as too cumbersome and unnecessary.

[Clay Fails]

I follow John Keeton's method for most bowls, but occasionally will also use custom made donut chuck in lieu of vacuum. Rarely use Cole style jaws, but when that is the best tool i use that as well.

[John Keeton]

To clarify, I don’t use vacuum with the Holdfast chuck. I just use it for friction and cushion. One could also turn a similarly shaped piece of wood and use a foam cushion to provide friction and protect the surface of the vessel.

[Roger Chandler]

To clarify, I don’t use vacuum with the Holdfast chuck. I just use it for friction and cushion. One could also turn a similarly shaped piece of wood and use a foam cushion to provide friction and protect the surface of the vessel.

The Holdfast vacuum chuck makes a pretty good jam chuck, 'eh John? I have used both my 6" and 3" so many times I have lost count. I do have the Rubber Chucky seals on them, and they do not mar the inside, generally, but if I am concerned, I use a mouse pad inside the bowl or on the face of the platter. Moderate tailstock pressure, and I mostly use my Oneway live center with the point in it....the outer diameter of the point holder makes a great gauge for the right size to begin taking the final nib down to where I take it off with a chisel, then sand & sign the bottom.

For deep bowls or vessels, I have a plywood disc with some anti-fatique mat glued to it with contact cement, and drew circles of different diameters on it.......sort of looks like a target, but with tailstock pressure against that mat and wooden disc, I have finished off numerous 3 cornered bowls, and other types of vessels, and of course I have a faceplate screwed onto the back to mount on the spindle. Works really well. I have found I don't hardly ever need a vacuum chuck, nor a donut [Straka] chuck.

[Mark Greenbaum]

John, it was a real pleasure to meet you last weekend at TAW Symposium. How do you make the bottom on that last photo with the eccentric rings?

[John K Jordan]

John, it was a real pleasure to meet you last weekend at TAW Symposium. How do you make the bottom on that last photo with the eccentric rings?

I enjoyed meeting you too! (And a number of other people.) I had a great time. I decided not to win the Powermatic lathe to give you a chance.

The multi-axis platter base idea is from my good friend Frank Penta:
http://www.frankpenta.com/index.php/projects/projects/Frank%20Penta%20Platter%20handout.pdf/detail
He uses a wormwood screw to hold the platter off-axis in three places to turn detail in the bottom. I decided to make that one a little different with a common flat bottom on each recessed turned ring - a little challenging but not too bad. I was surprised at how little wood was needed to to hold the big platter to turn the front. Sapele.

Oh BTW, I meant to post another photo of a recess I left in the bottom of some other platters. These platters are also sapele, 14" and 18+":

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JKJ

[Thomas Wilson80]

John -where did you hold the wood on this? On the inside of the large circle (expansion jaws)?
Thanks,
Tomhttps://sawmillcreek.org/attachment.php?attachmentid=378028&d=1517513790&thumb=1 (https://sawmillcreek.org/attachment.php?attachmentid=378028&d=1517513790)

[John K Jordan]

John -where did you hold the wood on this? On the inside of the large circle (expansion jaws)? Thanks, Tom

The chuck jaws are expanded in dovetailed recess at the smaller circle.
I think adding detail distracts the eye from the recess and it's far easier than reversing again to cut away the recess (and I'm lazy).

The recess is 3" diameter on this one and about 4-1/2" on the larger platter.

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JKJ

[Leo Van Der Loo]

Interesting idea Leo - I would have thought that those wood braces would either scratch or indent the bowl, but from the finished pictures that is clearly not the case. Might have to try that!
Thom I never had a problem with scratching the pieces, but if you don’t trust it you can easily glue some soft material on these frogs or just add some paper tape, that would already make it less likely to scratch the finished wood.

[Peter Blair]

A loose fitting jam chuck/piece of scrap wood shaped to fit a ring of contact at about 1/3 or more of diameter of piece and a piece of rubber shelf liner, leather, or other soft pad will drive the piece with pressure of the live center in tailstock. You can then turn and finish the majority of the bottom leaving a small nub (diameter determined by quality of wood) that should be cut off with flush cut saw with protective material against bottom or chisel. Breaking off the nub can result in tearing out the bottom. Also care should be given to the pressure on the tailstock with a thin bottom.

This is the method I use as well. I do sometimes use a vacuum chuck but thin bottoms and open grain wood will suction air right through the bottom.


That is the reason to always leave a center point in the bottom to align for remounting. This jam method works for all sizes and even natural edge pieces. A modification of method with longer jam piece can be used on hollow forms when support of top.

This jam method works vacuum will not work due to worm holes, bark will not fit cole jaws, out of round will not fit a donut chuck, ..............

I use the jam and nub method mostly as well. Sometimes a vacuum chuck if the bottom isn't too thin.

[Peter Blair]

Leo, any chance you might show describe how you made the extensions for your Oneway Mega Jaws?

[Leo Van Der Loo]

Leo, any chance you might show describe how you made the extensions for your Oneway Mega Jaws?

Peter I read your ??? but forgot about it, so I’m sorry for the delay.

I have 2 sets, but this one was closest and I just placed one of the pieces on the jumbo jaw plate, you can see that I only have holes drilled for anything larger than the regular jaws can hold, the the other set I made first from MDF has more holes farther out and I actually tapped thread in the MDF to hold the buttons, works fine and with longer bolts I can have nuts on the back side.

You can see that I used the long slot in the jaws to bolt the extension to it,rather than go trough the treaded holes, this works just fine for me on the Oneway Mega Jumbo Jaws.

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Maybe I should explain how I made it, cut a large circle of ¾” plywood on the bandsaw, laid the chuck with the jumbo jaws mounted and slightly open to mark the slot openings on the plywood and lines to saw the circle of plywood in 4 quarters.

Marked/numbered the pieces so they sit the same when mounted, drilled the holes for the bolds to go through the slots, outer holes bigger and deep enough for the bold heads to sit flush or slightly lower.

Mounted the pieces after they where sawn and trued the perimeter and scribed lines to drill the holes for the buttons and at the same distance apart.

Any other ?? just ask :)

[Peter Blair]

Thanks Leo