platter thickness and also spigot.

[Random Orbital Bob]

Hi folks, I've been experimenting with platters and I always seem to get them too deep. Can anyone tell me what the sort of standard (for say about 9" diameter) thickness a platter blank typically is please? Also how thick should the spigot for the chuck be? I'm currently making them in the region of about 5mm but I'm sensing they could be thinner than that and still safe. (The jaws I'm using have an optimal spigot diameter of 55mm).

Lastly, do those of you with platter experience tend to use spigots or recesses for the chucking and if so why do you prefer that method?

many thanks

 

[CHJ]

I usually start with 20mm thick blanks, 25mm rough saw at most.
I use sockets as they are a good guide to depth when cleaning up the base recess to finish off, with care they need not be full depth.

If using thinner stock than 22 mm then basically finish base and use a Hot Glue support for chuck register, mounted and turned true whilst blank mounted for base work. Mount glue block in chuck and complete top, reverse and turn off glue block and finish base.

Forgot: I don't buy Blanks for platters, I buy Planks and cut the circles myself..

 

[Random Orbital Bob]

what do mean by "sockets" Chas?

 

[CHJ]

what do mean by "sockets" Chas?

Dovetail Recess

You can see one here on these early platters I made before it was cleaned up.

 

[Dalboy]

I agree with CHJ about the thickness I have already rough turned 2 platters with a slight dish shape but have left them about 1 1/4" thick ready for final shaping and finish.

 

[petercharlesfagg]

Interesting question!

To my mind there is no set depth of a platter but I do think it is relative to its overall diameter.

Over the last 20 or so years I have forgotten how many platters have made but some of them have been 2 inches thick but the OD was about 18-20 inches or larger.

Likewise a 10 inch diameter platter is unlikely to be much deeper than 1.1/2 inches.

A platter anyway is only the description of the artist and then the purchaser!

Regards, Peter.

PS. I forgot the other section of your question. A socket or dovetail or spigot, whichever suits your own likes or nerves! The depth of the dovetail is, on average, about 4 mm, I don't bother measuring any more!

All my bowls, dishes and platters still retain the dovetail from the remounting, it is a useful space not only for possible remounting in the future because of damage etc. but it also gives me a recess for my business sticker, the name of the wood and the item number.

None of the hundreds of purchasers over the years have ever questioned it being there ONLY other woodturners!

 

[Random Orbital Bob]

Thankyou chaps.

Your comments about recesses made me smile Peter. I also tend to leave chuck recesses in my bowls if I'm going to give the piece to friends or family. If its destined for the turning club competition I have to reverse mount it and turn it off leaving the classic slightly concave bottom to avoid wobble. This is of course because wood turners arejudging the piece It seems wood turners take more professional pride in the art form than punters

Only problem is I find that if I leave the recess in I always find a slight denting occurs from the pressure of the jaws on the walls of the recess. Maybe I'm over-tightening but that's just a safety thing.

Also the recess thickness of 4mm is helpful as I do tend to go bigger than that (certainly for spigots any way). Its funny, I started always turning dovetailed recesses and I've switched to spigots of late and it wasn't a conscious decision, I appear to have drifted from one to the other. I think I'll cut blanks at 1.5" and see how that gets on. Mine were way too big, minimum 2 and sometimes more.

 

[CHJ]

....Also the recess thickness of 4mm is helpful as I do tend to go bigger than that (certainly for spigots any way). .....

For maximum chuck jaw support of the piece in work the recess needs to be deeper than the dovetail jaw, for a spigot it needs to be shallower than the dovetail jaw. the piece then has maximum support by being pulled up against the jaw face.

This is very relevant to stability when deep hollowing of bowls and forms.

On a platter though as long as the wood is a firm species (not spalted or soft) you can get away with a less perfect support because the bulk of the turning forces are across the face of the disc with little leverage from chuck axial overhang.
The Ideal:-

To increase the support area against the jaws when using a shallow recess I often use a thin plywood 'washer' between the jaws and the work piece.

 

[Random Orbital Bob]

Thanks for that Chas. That really reminds me now why I have been cutting my spigots too long. I think I've been mixing my rules viz-a-viz recess vs spigot. As mentioned earlier I started out always using recesses because when starting out I read they give a better hold to the work. Also there's nothing to turn off at the end if you're happy leaving the recess in the bowl. To satisfy the max holding strength rule I would turn quite deep recesses because my 2" std jaws on the SN2 (dovetail bit) are pushing 10mm so I was matching that with the recess. I've just realised that I've basically transferred that argument to spigots without catching up on any refresh of the rules. I've always known to butt the face of the chuck to the piece with spigots but I now realise I don't need that 10mm and 4 will do.

Thanks for that.

 

[Random Orbital Bob]

actually, now I come to think of it, that's why I switched to spigots in the first place. The recesses were too deep and it restricted how deep I could hollow the bowl. I was getting bowls that seemed "bottom heavy" ie there was still a good 5mm of hollowing to get done but in doing so I would risk cutting through the cavity formed by the recess. I switched to primary spigot use to avoid that. I think after this discussion I can return to recesses but with only 3-4mm depth on medium sized bowls without being too concerned.

 

[CHJ]

... I think after this discussion I can return to recesses but with only 3-4mm depth on medium sized bowls without being too concerned.

Make yourself a packing washer out of Ply or similar to take up some of you jaw depth for use with the sockets.
That will add some stability and allow shallower sockets. 10mm does seem overkill.