Segmented Platter.........Would this work........Maybe

[Tom Winship]

I need to build a platter and have this idea.

Why could you not start out with a center disc about 5" in diameter with a tenon for the chuck. Then glue a ring on some waste stock (with a glue block mounted to a face plate). Machine a groove around the ID of the ring approx 1/2 the ring depth and just a smidge larger than the center disc initially made. Now glue the center disc into the groove (maybe like a floating plug). Finish machine the tenon (without removing it) and the backside of the platter. Now remove the face plate and chuck on the tenon and machine the topside of the platter. Reverse again and remove the tenon.

Have I made myself totally confusing? I am afraid if you glued the central disc all the way around it would blow up the segment ring.

Think it would work?

[Dennis Ford]

I am a little confused on what this ends up looking like (and why) but the mounting sequence will certainly work.

[Tom Winship]

I am a little confused on what this ends up looking like (and why) but the mounting sequence will certainly work.

Dennis, I think I confused myself as well. The object would be to wind up looking like a platter, with a solid (non-segmented) center about 5" in diameter, surrounded by a segmented rim about 11" in diameter (segments 3" long). The center piece would serve as a tenon, glued into a mortise cut into the segmented ring (from "underneath"). Sorry for the confusion. Now I'm sure you really are.

[John Keeton]

Tom, I don't segment, but a 5" base of solid wood might risk an expansion/contraction problem unless it floats. 5" can move nearly 1/16" or more seasonally depending on species, and I don't know what that would do to your platter. Perhaps the segmenters will jump in here.

[Richard Allen]

It is important that the wood all runs in the same direction within 20 degrees. The woods should have similar expansion rates. you can try stabilizing the wood by soaking all exposed surfaces with a slow cure epoxy so that wood movement from moisture is mostly eliminated. But if the wood runs in different directions the plater will tear itself apart in a year or two.

Most finishes will seal up the wood and let you get a year or two out of the construction. But any finish will eventually fail enough that seasonal wood movement will be an issue.

There are charts available on the web for wood movement.

[Robert McGowen]

I would do it the way that you are describing with one additional step. I would make the tenon as long as possible. Glue up one additional ring that fits OVER the tenon and is big enough that the chuck would be able to fit inside it. Glue it on from the backside so that it covers the 5" disc and locks it into place. Basically a floating bottom disc technique, only you are fitting the disc into the second ring and not the first. You can turn the bottom cover ring very thin and then part off the tenon at a very slight angle so that the platter rests on the bottom ring and not the disc. The disc would be totally locked in and have a slot to expand or contract in. Only the segmented rings would be visible on the outside and the disc bottom would be visible on the inside. Bam! Might have to give this a whirl myself! :D

[Tom Winship]

Robert, just to make sure I am not confused, are you saying to make the disc(part 1), then turn a ring (part 2) large enough to fit over the disc tenon, and having a groove around the outside to receive the floating disc(part 1) glued on end grain only. Then make another ring (part 3) that would glue to part 1 forming the outer diameter of the plate? When looked at from the underside you would see the disc, but when looked at from the topside you would also see the disc, but it wouldn't be glued on the topside?

Part 3 inside would be smaller than part 2 outside and would be directly glued to it.

I hope this is correct.

[Robert McGowen]

Robert, just to make sure I am not confused, are you saying to make the disc(part 1), then turn a ring (part 2) large enough to fit over the disc tenon, and having a groove around the outside to receive the floating disc(part 1) glued on end grain only. Then make another ring (part 3) that would glue to part 1 forming the outer diameter of the plate? When looked at from the underside you would see the disc, but when looked at from the topside you would also see the disc, but it wouldn't be glued on the topside?

Part 3 inside would be smaller than part 2 outside and would be directly glued to it.

I hope this is correct.


Now I am confused! I know you are an engineer, so I am working on a blueprint for you to work off of! :)

PM'ed you.

[Michelle Rich]

A 5" diameter base is a no-no in the segmenting world. the expansion/contraction will cause huge problems. you can "float" that 5" in a slot..just like one would do in a panel in a door on a bookcase or such...Check out malcolm tibbetts book. he talks all about it there. his website might have something?? dunno

[Bill Wyko]

About the only time you can get away with grain in opposing directions, is if your segments ave very, very small and you turn very thin. Even then you should use woods with similar density. If you live in an area where your humidity radically fluctuates it will compound the problem. Keep in mind, Egyptians used wood expansion to split giant stones so don't underestimate the power of the wood. Here is a wood expansion calculator that may help.
http://www.woodworkerssource.com/movement.php

[Robert McGowen]

About the only time you can get away with grain in opposing directions, is if your segments ave very, very small and you turn very thin.]

like this???????

http://www.sawmillcreek.org/showthread.php?180585-Semi-segmented-platter-w-how-to-to-come&highlight=

[Jerry Wright]

Ah, the dangerous life of a contrarian. While being very much aware of the hazards of wood movement from decades of flat board work, I have successfully violated all of the rules when turning platters and shallow, large diameter bowls. I have made many bowl and platter shapes with segmented rims on single piece wood bases. As long as the wood used is well dried AND the segmented rim is glued on top of the base, then any moment seems to be absorbed by slippage in the glue line. Admittedly, I live in central NY where humidity may not fluctuate as much as other areas. I have successfully made segmented rings with end to end as well as cross grain glue-ups. You may feel the glue line with your finger, but never have had a separation. Drive fast, take chances!!!

[Tom Winship]

Okay, have decided with the help of my Texas Hill Country mentor to trap the disc between ring #1 (that the bowl rests on) and ring #2. When viewed from above, you will see the central 5" disc and the outer #2 ring. It will be in a groove like a panel in a door, (as you suggest Michelle).

It will "float" at Malcolm suggests. Will report back later.