Finishing the bottom of a very large platter

[Ed_McDonnell]

I have a 24" diameter slab of monkey puzzle wood that I want to turn into a platter. I have a 3520B with the lower bed extension. I do not have a vacuum chuck. I don't have a rim chuck that will handle a 24" rim.

My plan is to turn the piece outboard and:

1) use a faceplate to mount the blank and turn outside profile and the bottom leaving either a tenon for a chuck or a flat for a faceplate.

2) reverse the piece (mounting either with faceplate or chuck) and turn the inside.

3) scratch my head as I contemplate how to clean up the bottom.


None of the techniques I normally use to finish the bottom of pieces will work here. It's too big and the tailstock can't be used.

The only ideas I've come up with so far are:

1) to make very large ultra jumbo jaws from plywood and mount them to my stronghold chuck. I could see lots of potential for disaster here, but maybe someone has done it before.

2) use a grinder and carving tools to eliminate any tenon / faceplate holes and shape the bottom. This seems like cheating to me, but might be the easiest (if not the nicest looking).

3) forget outboard turning and the extra four inches and just make a 19.75" platter and turn it like I usually do them. Of course I would always wonder what it would have looked like with those extra 4 inches.

I'm open to any suggestions on how to proceed. Ideas anyone?

Ed

 

[John Van Domelen]

This might work

1) 1) Faceplate it and turn the bottom first - even the inside of the tenon that you will used to hold it, decorate the inside how you would normally, leaving the tenon long enough to have a lip and a flat surface for your chuck to grab hold of.

2) finish the back as you would normally

3) Reverse it - so the chuck is now holding the bottom by the extra bit of tenon, do the inside.

4) when complete - so long as the total width of the tenon is less than the width of a bench belt sander - just use that to knock down the extra lip on the base past where the chuck marks are. It wont take that long with a course grit and the decoration on the inside won't be damaged.

 

[Scott Blackman]

Carve/sand the bottom off and make it a footed platter....nice.

Another "more expensive" method would be to Vacuum chuck it to finish off the bottom. Everyone needs more tools.

Scott (Frostyford)

 

[hockenbery]

Ed,
drive up to Lakeland and you can use my lathe.
you might borrow someones lathe in your local club.

The method I'll describe will work and you will come close to getting a perfect center.

Turn at a fairly slow speed, take light cuts and don't get a catch. A catch might cause the platter to spin a bit and ruin the rim

Use high quality plywood (no voids) and make a disc 27" diameter or so. Mount it on a faceplate and true the rim. draw a circle that is the exact rim diameter. use hotmelt glue to put 12 small blocks of wood (1/2 x 1/2 x 1) just to the edge of the circle. the platter should then fit snuggly inside all these blocks. Actually you can glue the last 6 in place after the platter is on.

Tape the platter to the plywood with the strapping tape. the stuff with nylon strings.
Go around the back of the disc and over the platter. the wood blocks will hold it snuggly side to side and the tape will hold it against the plywood.
turn and sand away. The tape is not always needed but it sure is cheap insurance.

when you turn away the back use a little bevel pressure to push the platter toward the plywood. cut toward the plywood disc.


Happy Turning,
Al

 

[john lucas]

Since it's a platter there is enough room for your tailstock on the bed extension. you will have to build a riser but you could build it out of wood for a a one time use.

 

[robo hippy]

If you have big jaws for your chuck, say 4 inch wide or so, and dovetailed, turn a recess about 1/8 inch deep, and various beads, coves, lines etc. around and inside it. You won't have to turn it out, and it will look nice. I wouldn't be very agressive while turning out the inside, but I use this to turnand core bowls up to 18 inches with 2 5/8 inch jaws on my big Vicmark.
robo hippy

 

[Ron Sardo]

Here is what I've done to turn a few 14" platters on a 12" lathe

Face plate the blank and turn and create a 3/32" +/- recess for a chuck in expansion mode. Now turn and sand the outside to completion.

Now reverse the blank stick a sheet of paper towel into the recess and insert the blank onto a chuck. Now complete turn and sand the inside to completion.

Like I mentioned in my first sentence, my blanks where 14", not the 24" like yours. Your mileage may differ.

 

[MichaelMouse]

If you're set on a particular contour, you are going to have to work around the problem. I mostly just give in and make the recess for a dovetail. http://i35.photobucket.com/albums/d160/GoodOnesGone/Platter-Back.jpg http://i35.photobucket.com/albums/d160/GoodOnesGone/Birch-Back-Oil.jpg

If you're set on more elaborate bottoms, turn the upside, leaving a place for the same dovetail you'd have on the back, plus a half inch around. Mount, finish the bottom to taste, then chisel, scrape and sand the little ring back to flat on the face. Goes quickly and looks fine. The inside of this thing had a 1" dovetail plus an eighth removed after the bottom was smoothed to get it on its feet. http://i35.photobucket.com/albums/d160/GoodOnesGone/Cherry-Dish-Top.jpg

 

[John Van Domelen]

Very cool!

This is what I love about this site - ask a great question - get a bunch of really clever solutions! :cool2:

 

[Ed_McDonnell]

Thanks for the great ideas.

Thank you very much for all the great responses. I've got to decide whether this will be just a one time thing or if there are other large pieces in the future. I've got some big pieces of Mahogany, Rosewood and NIP that I'm now seeing in a new light.

For more than one time, Al and John's ideas would give me the most flexibility in turning the bottom and also offer the possibility of doing a large footed turning with a continuous curve to the bottom. More work to create the jig / riser though. I think between the two I would lean towards Al's. Having the tailstock available would be ideal, but I don't have the ability to fabricate anything in metal and a wood riser seems kind of iffy to me in this application. And if I'm going to put the effort into it I want to use it more than once. I would probably add slots to Al's jig and use bolt on wedges to lock the rim. One jig could do any size then. I'd still use the packing tape no matter how secure it seemed in the jig.

If I'm not going to do any more large pieces then incorporating an expansion recess into the foot design seems easy and relatively foolproof. Michael's idea that he used on his winged piece is intriguing, but I'm going with a high gloss finish and I want to have the inside of the piece flawless. I have a better chance of this by turning than grinding / carving.

Scott deserves an honorable mention here for his suggestion to add a vacuum chuck to my arsenal. I'll add it to my letter to Santa, but I'm not holding my breath.

Thanks All. I'll post my results.

Ed

 

[John Nicholas]

Use high quality plywood (no voids) and make a disc 27" diameter or so. Mount it on a faceplate and true the rim. draw a circle that is the exact rim diameter. use hotmelt glue to put 12 small blocks of wood (1/2 x 1/2 x 1) just to the edge of the circle. the platter should then fit snuggly inside all these blocks. Actually you can glue the last 6 in place after the platter is on.

Why not just make the bottom of a compression (donut) chuck for your 27 inch disc? You can spend your time with the blocks, hot glue and tape; or making a second disc.

Good Luck with your larger platter. You really need to do the large one.:cool2:

John 🙂

 

[Joe Greiner]

I've used a technique similar to Al's for bowls, but without the blocks, and using a disk just slightly large than the platter, say 1-inch larger diameter. And lower-quality plywood works just as well. Turn a groove in the plywood to mate with the rim of the platter; true the groove region beforehand. Wrap the tape across the finished part of the bottom, both ends of the tape around to the back of the plywood disk; staple on the back of the disk for insurance. The tooling takes only minutes to prepare, and the interior of the disk can be re-used for smaller projects. With light cuts, turn any shape you desire on the bottom. For a variation, see "Lathes and Turning Techniques; The Best of Fine Woodworking" by Taunton Press, ISBN 1-56158-021-X, page 111; article by Betty Scarpino; no original citation, though. I think I've seen something like it elsewhere, but can't remember where.

Joe

 

[George Guadiane]

Thank you very much for all the great responses. I've got to decide whether this will be just a one time thing or if there are other large pieces in the future. I've got some big pieces of Mahogany, Rosewood and NIP that I'm now seeing in a new light.

For more than one time, Al and John's ideas would give me the most flexibility in turning the bottom and also offer the possibility of doing a large footed turning with a continuous curve to the bottom. I would lean towards Al's. Having the tailstock available would be ideal, but I don't have the ability to fabricate anything in metal

Scott deserves an honorable mention here for his suggestion to add a vacuum chuck to my arsenal. I'll add it to my letter to Santa, but I'm not holding my breath.

Thanks All. I'll post my results.

Ed

Ed,
I have several steel tool rests assembled from scraps by my local steel fabricator, and QUITE reasonable. You could have a riser made from square stock (I am guessing...
The metal might not be good for heavy duty stuff, but for your purposes, that might be an inexpensive reusable solution.
Does anyone know if there is a bed extension for the 3520A?

 

[John Van Domelen]

I had thought the one for the B would work if holes where drilled in the frame to bolt it on. I may be mistaken - but I thought I had read that - maybe on the Mustard Monster site.

 

[John Nicholas]

Does anyone know if there is a bed extension for the 3520A?

Yes, The same extension fits both the A and B models. The B model legs have two sets of holes to fasten the extension to. One is level with the 35 inch bed, the other is 18 inches lower. On the headstock end of the B model, you use the lower set of holes to fasten the tool rack to the legs.

John 🙂

 

[Walt Schubert]

turning a large platter base

One solution to turning the bottom of a lare platter, which is fairly simple is to mount a circle of 1" thick MDF which is larger than your platter to a faceplate.

When you mount the MDF to the faceplate, use through bolts with a countersink head. Countersink the MDF. Put the bolts through the MDF and then the faceplate. I prefer to use lock nuts on the back side of the faceplate. (Do not attempt to hold the MDF to the faceplate by using screws into the MDF. That is a recipe for disaster!

This is a rather heavy setup, so, use the set screws on you faceplate to lock the faceplate to the spindle. Otherwise, when you stop the lathe or reduce speed, you stand a chance of the faceplate unscrewing from the spindle.

Make some hold downs from wood with a soft pad on one end (I used carpet padding obtained from a local carpet place) to be used on the MDF to hold the platter in place by its outside edge. Any shape hold down should work. I made mine similar to Incra hold downs only constructed from scrap wood.

Mark a few penciled circles onto the MDF as guide lines to help locate the platter in the center of the MDF.

Mount the platter and go to it!

You could use this method to turn virtually any sized diameter, but keep your speeds down!

Walt

P.S: If you turn the outside edge of the MDF round, be sure to use a breathing mask and eye protection. MDF generates a huge amount of dust when turned!

 

[potter142]

large Platters

Mount the blank on a face plate, turn the outside leaving a food with an internal lowered area. Under cut the inside of the foot for dovetail expansion on your
chuck. turn the platter over, turn the inside but leave a spigot so you turn the platter over and completely finish the outside. With that done remount the platter using the dovetail mount, remove the spigot from the inside and finish.
Always works for me.