Turning the Bottoms of Vessels question

Dan Mosley

Member
Messages
1,169
Location
Palm Springs, Ca
I was wondering how some of you part off and flatten your bottoms on your vessels.

Currently when im done hollowing, I reverse the vessel and put it on a mandrel I have that has a long bar that will hit the bottom of the vessel and a cone in front that secures the opening. I then move the tailstock up to the rear securing it to the spur drive hole. It aligns it really well and I then turn it down between the waste block and the bottom of the vessel to a very small nub. At that point I saw it off and sand the nub down with a sanding flap wheel or sometimes take it over to the drill press and sand it flat with a small disk sander chucked in the press.

However, today I had a large vessel I had parted off and the best way I could think of to sand the bottom and keep it flat was to use the drill press with the disk mounted in it and hold it with both hands and sand it flat. It worked out "ok" but it took a bit of work because it is easy to not sand perfectly flat when your holding it and touching it to the spinning disk.

See pictures below of the Mandrel (Picture #1) and another project (unfinished) showling the tennon I leave before parting off.................

Anybody else doing it differently? and can you explain in some detail ? Im game to try another way.............LOL
 

Attachments

  • Natural edge vessel complete mandrel.jpg
    Natural edge vessel complete mandrel.jpg
    79.4 KB · Views: 82
  • Dyed-1.jpg
    Dyed-1.jpg
    68.9 KB · Views: 83
If I'm not using a vacuum chuck, I reverse the piece into a friction chuck, using the tailstock to keep it in place. For friction chucks, I'll use a variety of off-casts or failed turnings laying around the shop. Roughed-out bowls work great...just true them up and put a piece of foam between the bowl and the vessel. I turn the tenon down to a concave foot, leaving a small conical nub, power sand any parts that I was unable to reach when it was on the chuck, then cut the remaining nub down to 1/16" or so wide at the foot with a detail gouge. I stop the lathe, remove the piece, trim off the nub with a swipe or two from a sharp chisel, then finish sand the foot, either by hand or with my 2" ROS.
 
I usually use an inside expanding jaw chuck or a Cole chuck to finish bottoms. The distinguishing characteristic of this technique is that just as I am about to finish the turning often breaks loose and flys across the shop, usually breaking in the process. (I didn't say I was good at making bowls, did I?) Does that explain why I don't post pics of my bowls very often? :eek:
 
Vaughn - Yeah that is about how I do it - sharp chisel would work well but I have been using a small Colt hand and cutting the little nub off and then sanding. Sometimes i have used the base of the drill press to hold the vessel down firmly on with my hands and just move the bed back and forth as the sanding disk sands on the bottom of the vessel - which works very well for keeping it level on smaller vessels. Other times I do it like you mentioned except I used the mandrel to hold it.
The last couple vessels have been large diamter ones measuring about 13-14" diameter and a bit taller. I had turned them to finish from wet and let them dry. I should have left the tennon and let them dry then part off but, I didn't and got some warp on the bottom so to sand it level on the press setup which was a pain but, I finally got it sitting without rocking around.


Frank - I could have made a compression (donut type) jig and did it that way but I didn't want to spend the time I guess to fool with it for this one vessel. I do have this type of jig for bowls though.
Cole Jaws - I do not own them - I have thought about it but on my Super Nova the will only hold up to 10" diameter as I remember, and I hear alot of complaints about them so I never have bought them. I am not so sure of the holding grip on vessels with them if you see how the tops are formed alot of times - I wouldn't think they would hold well at all. But for machined edge smaller bowls I can see that they would probably work well.
 
I'm not so sophisticated in my turnings as you and Vaughn... I don't do a lot of hollow forms, but when I do, I do pretty much like Frank... I use a compression chuck or pin chuck to hold the mouth will I fix the bottom....

On Bowls, since I don't own a vacuum chuck, I use a cole jaws if the bowl is small enough or a Longworth if it's to big for the cole... I just bought an extension for my cole chuck but haven't tried it yet... I'm thinking it may be too big to work over the ways on my Jet 1442... may have to swing outboard with it to do the bottoms... instructions say you can band saw them down to fit, but don't think I want to go cutting on them and risk getting out of balance.
 
Chuck - I have a Jet 1642 with a super nova chuck.....Last time I checked into it the cole jaws for the supernova limited you to 10" diameter as I remember.......or are you talking about a different chuck?
Then again, I suppose you can make a set to hold a larger diameter................
 
Last edited:
Chuck - I have a Jet 1642 with a super nova chuck.....Last time I checked into it the cole jaws for the supernova limited you to 10" diameter as I remember.......or are you talking about a different chuck?
Then again, I suppose you can make a set to hold a larger diameter................

I use one of PSI's Barracuda chucks and the Cole that fits it is limited to 8".. but PSI has recently started selling a Cole jaw extension that will open to about 16 inches... it's a high impact plastic that supposedly can be cut on a band saw ... but don't think I'll cut mine.. should be able to just turn outboard to clean up the bottom.
 
Just finished the bottom of a compilation work today. I'll post the bottom here later for example, but the "cut it close, knock it off and sand it" works very well. Cuts down on a lot of extra business ;)
 
Dan, fact is, I'm not a patient person.
Usually my flying objects result from that lack of patience. I'll make a decision to take "one more" cut a bit deeper than intelligent thinking should allow and 'voila' flying object. If I did it right and kept cuts to only light scraping and sanding I would have better success.
Cole jaws are not designed for that 'one more' deep cut. :eek:
 
Frank.............yeah but if on a bowl for example I reverse and turn the tennon down to a small nub - I was thinking then I could use the cole jaws and they would allow me make some light finishing/leveling cuts on the bottom of bowls and then sand it and call it done......but I have no experience with cole jaws. I agree that cole jaws are not meant for more aggressive cutting...................
 
Last edited:
Frank.............yeah but if on a bowl for example I reverse and turn the tennon down to a small nub - I was thinking then I could use the cole jaws and they would allow me make some light finishing/leveling cuts on the bottom of bowls and then sand it and call it done......but I have no experience with cole jaws. I agree that cole jaws are not meant for more aggressive cutting...................

Neither are the Longworth's.... and I've had the black eye to prove it..:rofl::rofl::rofl:
 
Neither are the Longworth's.... and I've had the black eye to prove it..:rofl::rofl::rofl:

Same here, but it was a bruised forehead. :doh: The infamous "one last cut". :rolleyes: That was also the occasion that convinced me to wear a face shield more consistently. Since then, I have no desire to use a Longworth chuck without the tailstock in place for anything other than slow speed sanding (and I'd do the same with Cole jaws too, for that matter). Heck, I use the tailstock up to the last minute with a vacuum chuck, too.
 
Same here, but it was a bruised forehead. :doh: The infamous "one last cut". :rolleyes: That was also the occasion that convinced me to wear a face shield more consistently. Since then, I have no desire to use a Longworth chuck without the tailstock in place for anything other than slow speed sanding (and I'd do the same with Cole jaws too, for that matter). Heck, I use the tailstock up to the last minute with a vacuum chuck, too.

Same here... I even use the tail stock when I start hollowing a bowl until I get about 1/2 way into the bowl, then I'll pull it back and finish without it. I wouldn't say we're getting gun shy, maybe finally had some sense knocked into our heads??? :rofl::rofl::rofl:
 
Top