Question about Reverse Chucking

[Hilel Salomon]

How do you folks finish the bottoms of your bowls? I usually use a faceplate and create a spigot (dovetailed if I'm going to use a Nova or Vicmarc and straight if I'm using a Oneway) turn it to more or less the shape I'm want, put it on the chuck and hopefully finish hollowing it, sanding and finishing it. Then, ugh I have to face doing the bottom! I've sanded it off, tried to use cole jaws, a grooved plywood and a few other ways, but I never get a very good result. Right now, I have about a dozen bowls that need their bottoms finished.
I've hesitated getting a vaccuum system-but I'm not sure why?
I see such beautiful work being done by most of you and wonder what techniques you use?
Thanks, Hilel.

[Ken Fitzgerald]

Hilel....I made a donut chuck out of 2 pieces of plywood. A solid piece turned round attached to the face plate. A 2nd piece with a hole turned in the middle is bolted to the first piece with the bowl to be finished captured between the two pieces. I use my tailstock and the mark on the bottom of the bowl to get the bowl centered between the 2 pieces of plywood. It takes a few minutes to get the bowl centered and then tighten the bolts and turn the bottom, sand and friction finish if doing so.

To use it for NEs I use double sided tape to tape several layers of 2" styrofoam insulation to the base piece of plywood...enough to hold the NE proud of the base piece of plywood......turn them round or cone shaped...put the NE over the styrofoam......capture it and then finish turn the bottom of the NE.


I hope this makes sense.

[Dario Octaviano]

Ken, If you get one of these... http://bestwoodtools.stores.yahoo.net/tailchucad.html

Your alignment will be perfect each time and fast too ;)

[Bernie Weishapl]

I use the donut chuck and Cole Jaws. I have the Vicmarc Cole jaws which I really like and will hold bowls to 14". When using the donut chucks (I have 2 sizes for 2 different size lathes) I always make sure I leave the livecenter mark on the bottom when I had the blank on a faceplate. That makes it sooooo much easier to center in the chuck. I also use styrofoam on my donut chucks when doing NE's to keep them proud of the base piece just like Ken does. Both work pretty well for me. I used the donut chuck for a long time before I got the Cole Jaws for my Vicmarc.

[Ken Fitzgerald]

Thanks Dario! I'll bet that will speed things up!

[Gordon Seto]

Vacuum chucking is the most convenient of them all. But you still need other reverse chucking methods, because you can't use it when there are voids, bark inclusion porous bowls.

Gordon

[Andy Hoyt]

Jamb chuck. Free!

[Dario Octaviano]

I use both jamb chuck and before...donut chuck. Haven't make a donut chuck for my new lathe though.

Vacuum chuck is on the horizon...if I can get my lazy butt start working on it! :D

[Jim Becker]

If I'm not using vacuum, I use the Ellsworth method...turn a "blob" that will fit into the vessel, put some soft material on it, like foam padding, put the piece back between centers with the tenon toward the tailstock, get it as close to centered as possible and then trim off all but the smallest nub with gouges, parting tools and a specially ground 1/4" spindle gouge (another Ellsworth idea). You can actually part it off if you have a true variable speed machine that you can slow down to almost nothing at the end as I do, but a small nub can be removed with a simple carving gouge or a chisel. You can do a nice undercut rim on the base this way if it's appropriate for the piece, too.

[Travis Stinson]

Vacuum chucking is the most convenient of them all. But you still need other reverse chucking methods, because you can't use it when there are voids, bark inclusion porous bowls.

Gordon
Vacuum chuck hands down! Blue painter's tape is your friend. ;)
This one was reverse chucked in a vacuum chuck.

[Bernie Weishapl]

Travis are you spoofing me???????? Don't be messing with me. How did you do that with a vaccum chuck.

[Hilel Salomon]

Thanks to all of you. I'm going to try the donut method and use the cole for smaller pieces. I will, though, break down and get a vacuum chuck. Have a PM and a Nova DVR, both (one in Cola, one in VA) and both have wheels on the headstock. Will I need special adaptors? What's the best vacuum system around? I'll get a Gast from my local dealer, but would like a system for the mechanically impaired-ME!
Thanks again, Hilel.

[Mark Pruitt]

Ken, If you get one of these... http://bestwoodtools.stores.yahoo.net/tailchucad.html

Your alignment will be perfect each time and fast too ;)
I would assume that using that accessory requires a vacuum chuck, right?
(With bowl still mounted in scroll chuck, remove scroll chuck and screw onto tailstock adapter, install vacuum chuck, bring bowl up to vacuum chuck, turn vacuum on, release scroll chuck, remove tailstock and finish turn bottom of bowl):confused:

[Ken Fitzgerald]

Mark.....You'd leave the bowl on the chuck...Unscrew the chuck....screw this adapter into the chuck....Place outer ring of your donut chuck over the bowl......put the entire assembly in the tailstock...mount the base of the donut chuck (on you faceplate) on the headstock.....bolt the outer ring of the donut chuck to the base and you have your bowl centered and captured..

In short it would center your bowl on the donut chuck by leaving the bowl attached to your chuck until captured by the donut chuck....I hope this makes sense.

[Paul Engle]

Hilel, I use a wood worm screw in the bowl face backed up by tail stock , I turn the outside shape, then recess , sand and finish , remove from wood worm screw ,then chuck bowl by bottom ( as is done) finish outside, then shape the rim then hollow the bowl , sand , finish. nothing fancy and I only have to flip it once.If you put a foot on it then you turn the foot before you flip it, jam chuck and remove the tennon ,sand, finish. Most of my bowls etc use recess so I do not have to go back.If I turn the foot after I make the recess then flip it but I dont like to do that so most of thetime I use recess with the bottom flat for a foot.

[George Tokarev]

Similar to Paul, I finish the recess in advance, fancy it a tad if I think I want it that way, and let it alone. Few beyond other turners will care if the bottom's jazzed, because to see it their guests would have to spill the beer nuts.

Only weak spot in this method is wet and warp stuff, where you will have to sand the bottom to sit flat as a minimum, and leave it a bit oval after drying. I can live with it, but if it's not your thing, be sure to leave a witness mark for center and use it to snug the disk or vacuum chuck you're using to hold it to refinish. When I use it, I do a tapered disk and hot glue. Then I have to decide if I want to blend the new bottom with sandpaper or not. Makes leaving it oval my favorite method.

[Mark Pruitt]

Mark.....You'd leave the bowl on the chuck...Unscrew the chuck....screw this adapter into the chuck....Place outer ring of your donut chuck over the bowl......put the entire assembly in the tailstock...mount the base of the donut chuck (on you faceplate) on the headstock.....bolt the outer ring of the donut chuck to the base and you have your bowl centered and captured..

In short it would center your bowl on the donut chuck by leaving the bowl attached to your chuck until captured by the donut chuck....I hope this makes sense.
Ken, thanks.
OK, then basically what you're looking to accomplish with this is to center the bowl "perfectly" in your donut chuck. I've found a much easier way, at least it seems easier to me. At the time I glue a sacrificial block to the base, when I go to true it up before reversing, I will take a point-nose scraper and turn a v-shaped indentation in the very center. Then, when I'm finished hollowing and ready to reverse it for turning off the sacrificial block, I use my live center in my tailstock to center the bowl in my donut chuck, using the previously turned "v" for reference.

Come to think of it, this method would also work for centering on a vacuum chuck. Hey, wait a minute. That's one less thing to buy! That can't be right!:p

[Ken Fitzgerald]

Mark...I used the mark made by the point of my live center to align it but still getting the bowl centered at the other end (the top of the bowl) presents the problem. By using the chuck as with the tool Dario showed, it's held in proper positioin the whole length of the bowl.

[John Hart]

I do Jim Becker's blob/jam method every time. I'm pretty comfortable with it.

[Dario Octaviano]

I do Jim Becker's blob/jam method every time. I'm pretty comfortable with it.

I do too...actually I use the chuck itself (padded) as much as possible.

[John Hart]

I do too...actually I use the chuck itself (padded) as much as possible.

Yep...me too. I've found that the most critical thing is having uniform thickness in the padding. This is where the mousepad comes in handy. Plus I open the jaws just a bit on the chuck....for "bite" into the mousepad

[Travis Stinson]

Travis are you spoofing me???????? Don't be messing with me. How did you do that with a vaccum chuck.
Now I wouldn't do that Bernie.;)
As long as the seal around the mouth of the chuck is good, just cover any opening, voids, etc. with the blue painter's tape. It's nice and strong and doesn't leave any residue on the turning. You do have to keep an eye on the amount of vacuum you're pulling, so you don't implode the tape. Usually around 10hg. is enough to hold something like this good enough to finish off the bottom and sand.

[Andy Hoyt]

I've found that stretch wrap film works pretty good too. And it's cheaper than that blue stuff.

So there, Trav. Ninner ninners.

[Ken Fitzgerald]

Hoyt....ninner...ninner must be a Hoytism.....everybody knows it Neener..Neener....:rolleyes: