finishing teh bottom of large bowls or platters

[John Nowack]

I was looking a thr show stuff from Matt Hutchinson,s post...My mother would love a large (platter/shallow bowl not sure what qaulifies but hopefully you know what I mean)---Matt if you read this do you have a vacum chuck or how do you finish te bottom??

I have a delta mid-size lathe but I can slide it to the end or tilt it for a larger peice I think (now that I think about it I would have to have a tenon on it to do that and I would only be able to turn somthing 14inches at best)

After all that I guess I change my question---there is probably no way to turn anything larger than the swing of your lathe is there?

she wants a center piece with some spheres for a large dinning room table

[Bernie Weishapl]

John if you have the delta midi I think that is the LA220 which I also had you can only turn 10" on that lathe. My Rikon can turn 12" so that is the biggest I can do because of the fixed head.

[Paul Girouard]

No outboard capability on your lathe's?

My Record has a swivel head so I can , they say, do a 30" round turning:eek: It would have to be very light and well balanced to do that.

[John Nowack]

it has a 14" swing but it slides on the bed and pivots to the side as well---just tought of something else---I have never used a face plate but I geuss I could use that at the end of the lathe to turrn on a tenon and then reverse it---now I still have the probelm of turning the tenon off or finishing the bottom----I usually use jumbo (collet?) jaws or a jam chuck-I don't see it being possible to jam chuck somthing like a platter

maybe she just gets a bowl this year

[Paul Girouard]

Could you turn a shallow recess like Leo showed me on his thread and use a chuck?

[Grant Wilkinson]

John: You can make a donut chuck quite easily and turn the tenon off that way.

[John Nowack]

sorry don't see a link thanks

[Paul Girouard]

sorry don't see a link thanks



I had to go eat my wife was calling me, sorta like when I guy was a kid around here , nothing interesting happens till suppers ready :D


This thread ,

http://www.sawmillcreek.org/showthread.php?t=91653

http://homepage.mac.com/l.vanderloo/PhotoAlbum26.html

The second one's the photo link if it works , if not click on it from his org. post. His post #6 and open the photo link Leo posted , some excellent "how he does it" photo's , really helped me "see" how to do some things anyway.

Like Leo said HTH:)

[Leo Van Der Loo]

Hi John
What do you call "large" also what's the lowest speed on your lathe ?
Also your tool rest how and where are you able to put it, can you reach far enough and will it still be stable ?
If all the above are within the limits, there are several ways to go at it, easiest IMO would be to first cut the disk as exactly round as possible (for balance) then screw it onto your faceplate and shape the outside/bottom of the platter/bowl, do all the sanding and finishing before you take the piece off of the lathe.
To be able to do the top/inside you can make a recess that would look OK as a foot later, whatever you decide try to get a foot/base now so you wont have to try doing it later with all the problems of holding and centering it.
If you don't feel safe with the recess, you can hot glue a tenon onto the platter and you can heat and release later and scrape/sand the base clean.
Hope you have a chuck, but if not, a good faceplate can be screwed on now, onto the tenon, scribe a circle just larger than the faceplate so you can center it and screw it on.
Then you do the other side, should work if you are careful :-))

[Matt Hutchinson]

Well, according to what you have said, your lathe might be able to turn a 12" shallow bowl or plate. Power and speed are of concern, but if you take light cuts and you can go down to 500 RPM you might be ok. I say might, cuz a piece of wood at that size on that lathe would have to be mighty balanced. You probably have heard of the speed equation: RPM x work diameter = 6000 to 9000. 500 x 12 = 6000, but this rule doesn't exactly apply to bowl turning, especially while the blank is out of balance.

As far as the finishing the bottom question, there seems to be four main ways (not including vacuum chucking).

1). Padded friction chuck, the bowl being held by the tailstock against a padded convex shape the entire time. Turn the foot, and remove the nub from where the tailstock held it with a chisel or something. A catch could send it flying even with tailstock in place. I have done it myself. This method does not give full access to the foot for finish turning.

2.) Cole jaws for your chuck. You still want to use the tailstock as much a possible. Gives full access to the foot, but not until the tailstock is backed off. No tailstock use is risky, and a catch could easily send it flying.

3.) Longworth chuck. Very cool chuck, like Cole jaws but better....maybe, and you can make one yourself using a faceplate. Gives full access to the foot. Never used one, but I think a catch can still send a piece off the lathe. I believe there are bolts sticking out behind this chuck, and you don't want to reach behind it while it'e spinning.

4.) Donut chuck. The ultimate in safety in cases of a catch, and easy to make using a faceplate. You still use the tailstock to center the piece, but mostly held by pressure between the surfaces. Also, you have full access to the foot. But there are bolts sticking out behind this chuck, and you must remember never to reach behind this chuck while it's rotating.

For this show I didn't want to have to worry about catches on the feet. I was getting worn out, and that usually means silly mistakes happen which will send pieces flying, so I built my first donut chuck. It worked great, but it does have some weaknesses. For super large stuff I like the security of it.

There is a lot more info on these foot finishing processes in other threads, and there's a lot elsewhere online too. Hope this helps!

Hutch

P.S. In the pics the bowl is 20" in diameter, but that is the chuck I used for all the bowls. I simply made a second outer ring with a smaller hole for the smaller pieces.

[scott schmidt grasshopper]

two points for you . one if your headstock slides down the bed then you can put a riser under it . ( I build one at the local machine shop. ) 4 inch high chunkO steel or aluminum with a slot and tenon in it ( worked for my delta700 with reeves drive) doesnt increase the weight capacity but does increase the diameter,
second make a donut chuck. a change I havent seen is I used a 1x10 oak board for the base plate and then cut circles from some 3/4 signboard ( with a smooth surface) when I cut the rings I used a jig saw on a bevel so that one inner ring hangs up on the next ring bigger. so I can do the bottom of a small bowl with only a small ring, or can stack rings to get from the "holding point" to clearance on the rim. I have six or more differant length 1/4 stovebolts so I dont have much protrusion of bolts out the back and use wingnuts to tighten. hope this helps, oh use felt to cushion the ring/bowl contact.

[Wally Wenzel]

Scott, A little thick this morning but i don't quite follow you on cutting the rings for the chuck, would you have some pics. I have a donut chuck but what you have sounds interesting. I hope you can clear it up for me. thanks, Wally

[John Nowack]

you took my thought process several differnt places I could not visulize at first----I have visualized what direction I want to go--now I just need to educate my self a little further on the technical set up so the process is safe (this part is a little harder for me and the technical stuff is not what I have fun building and creating)--I knew I should never have cheated on all that algebra, geometry and drafting home work that I was "never going to use anyway";) Probably spent to much time in the AG/FFA shop welding goose necks and horse trailers together so I could have some fun money

[scott schmidt grasshopper]

Scott, A little thick this morning but i don't quite follow you on cutting the rings for the chuck, would you have some pics. I have a donut chuck but what you have sounds interesting. I hope you can clear it up for me. thanks, Wally

sorry no camera or cell phone. but here goes
take a piece of 3/4"plywood and your dividers. make circles about 2 or 3inches apart, ex: dia.#1-4 ", dia.#2-7", dia #3-10" etc.
then use a drill to make a jig saw blade start hole at a say 20/30 degree angle. insert jig saw ( also set at same angle) and cut out your circles. . if you have a 12 inch lathe then outer circle is 11.5 and a 90degree cut.
make a base plate or use a 1x10 and either mount it to a faceplate or as I did turn a mortise for my chuck . install on chuck and true up the outer face( away from the headstock )
dismount the base, set on table face up,and set the stack of rings on top of base be sure angles are in order so one ring is captured by the next larger ring.
drill 1/4 inch holes thru each ring and base ( 4 each be sure holes are towards the outer edge of ring) remove rings and redrill base holes 1 size larger ( gives adjustment to rings)
get some 1/4"stove bolts from 3 to 8 inches long and wing nuts
also a couple pieces of roof felting or something like it tshirts work also
make your happy bowl and sand except for finishing the foot
place bowl rim down on base then select ring that gives access to bottom . make and place felt ring between wood ring and bowl.next, if bolt holes do not clear rim then put next size ring on top of first ring the angled slopes of rings will hold the smaller one.
when you have it all ready to clamp make sure rings are even and tighten wingnuts abit.
mount on lathe. bring up tool rest or tailstock and check for bowl being centered, if not then loosen wing nuts abit and adjust . I normally barely snug the nuts then bump the bowl by hand untill its very close. once centered tighten nuts. do not overtighten or cracking might result . you can now turn and sand the bottom
options, sand the rings for smoother surfaces ( and doesnt catch your hide if you touch it .) label or mark the orientation of the rings so holes line up
make up 2 or more of these so small bowls dont need huge spinning things to do 'em
if the rings dont work well for a odd shaped bowl turn the inner ring over
when not in use I place the felt rings for this set inside then all the rings in order and add 2 bolts to hold it all together for storage.
muddy enough ?

[Wally Wenzel]

Hi Scott, thanks much for the indepth instructions i think i have it figured now, you threw me in the first deal about the angled cuts but that makes a lot of sense now. Thanks again Wally