Base or Bottom but how to do it?

[John Shillabeer]

This is a cry for help.

Using a faceplate I have just mounted a 24 by 2 inch disc on my Nova DVR lathe intending to make a shallow bowl or platter. It was ready for turning when I realised I did not know how to finish the base. The disc is of such a diameter that I have turned the headstock at 90 degrees to the lathe bed and will use the out rigger to support the tool rest. Of course the tail stock will not be available to support the work piece.

It seems to me that I have three options, but all have their disadvantages:

1. To begin with I can turn and finish a mortise or a tennon for the base, hoping that the chuck does not damage it beyond my ability to touch it up afterwards by hand.
2. I can make a large MDF disc and tape the finished work piece to it with the base exposed. Then gently smooth off the base. Using this method, I lost a bowl that broke the tape and took flight only to crash and smash on the floor.
3. I can use a thick glue block and, if it is thick enough, avoid reversing the work piece. I would separate the glue block from the work piece at the end of the turning and finishing process, leaving a plain flat bottom. I think I would have to use a glued paper joint, but my limited experience with this method has not been very good. The joint seems not strong enough for largish pieces.

What would you do?

John

[Roger Chandler]

If this were me doing this project, I for safety reasons would lessen the diameter to where I could use tailstock support. Something you may not want to do, but if you can secure the platter to a plywood disc, using about 10 -12 "L" shaped hold downs with screws and get it perfectly centered, then you could turn the bottom. You want to use plywood, not mdf if possible because mdf will flake out and plywood will hold screws pretty well...........

Whatever you decide, please be safe........a platter this size coming off could really do some damage if it hit you!

[Wally Dickerman]

I agree with Roger, 24 inches is too large for your lathe. You'll find that extending the tool rest that far will give you a lot of vibration and chatter when you use a tool. I also agree that you should have tailstock support. Securing a platter to the lathe has some options. I suggest using a chuck in an expanding mode. For a large platter you'll need a heavy chuck and large jaws.

You mention using a glue block with a paper joint. Not safe on a piece that large. The paper is used so that the piece can be removed easily. A catch and it might be removed before you want it to.

[Dennis Ford]

I agree that this is stretching the capacity of your machine but it can be done. If it is also stretching your capabilities at the same time, proceed with extreme caution.

Option 2 would be my choice. A shallow recess turned into the MDF that fits the rim and few globs of hot glue in addition to the tape would be a good idea.

[Thom Sturgill]

Option 4 - Doughnut chuck.

Use a large (not deep) recess. To follow the 40% rule you would need 10" jaws. I would want at least 7". Clean the inside of the dovetail as well as the rest of the back before reversing it and leave the recess in the platter. If you do feel the need to remove the recess, a doughnut chuck would hold the piece without tailstock, but it would be very difficult to get it centered.

[Shawn Pachlhofer]

option 1 - turn and finish the recess - for the LARGEST set of jaws you have. measure your jaws for the "perfect circle" diameter. This usually very near closed, with 1/16" - 1/8" space between each jaw.

if you chuck up using that sized recess, you will minimize the damage to your piece.

[Bob Bergstrom]

Best option buy a bigger lathe? Maybe someone in your area might have a big enough swing to help. Another reason clubs come in handy. You may have to travel some distance in the BC though??

[Sparky Paessler]

I have a nova DVR with the outboard turning attachment and have done some 20" platters with it. I used a faceplate and turned the Outside/Bottom of the platter and like several said turned a recess into the foot. I then used a chuck in expansion mode to hold the foot while I turned the inside of the platter. Be sure to leave a fairly wide "foot" around the recess so that you dont break the recess out. The outboard turning attachment on the DVR will give you good support for the tool rest even going up into the 20" range as long as it's a very shallow bowl/platter. All the ones I have done have only been 2 to 3" deep. I did use a large faceplate for the extra support when roughing it out since you don't have a tailstock supporting it. All that said I would only recommend doing it if you feel comfortable with it. I had done a lot of turning before trying it and kept the rpm fairly low and used a good facemask. My lathe is also mounted to a large heavy bench that I have a couple of 80LB bags of concrete on a lower shelf for stability. I should probably add that I used a chuck that had dovetail jaws and turned a dovetail into the recess. I think it in this application would hold better that the straight jaws.

[Leo Van Der Loo]

John this is the way I do these things, as I have no tailstock on my outboard setup where I do my larger turnings.

Cut out a disk that is a couple inches bigger than your bowl, (see pictures) I like to use pine boards, but if you use long enough screws you can use plywood (plywood can delaminate).

Screw the disk to the faceplate, turn a bit of a recess in the disk to fit the bowl, and just deep enough so the bowl can’t slide around.

Make a few fingers that will be screwed onto the disk to hold the bowl down, you will have to decide how thick and wide and long, as it has to fit your particular piece.

Finish turn the bottom as you like it to look, sand and polish, all done

Safe holding option.jpg Returning options.jpg

[Roger Chandler]

Thanks for the pics of this Leo.......the "L" shaped hold downs I was referring to in my earlier reply are very similar to what you have shown here in these pics, only with a thicker area where the screw head would be and the longer screws to go through the plywood layers. I should have mentioned a thickness of 3/4" on the plywood disc........nothing less in my mind!

[Leo Van Der Loo]

Thanks for the pics of this Leo.......the "L" shaped hold downs I was referring to in my earlier reply are very similar to what you have shown here in these pics, only with a thicker area where the screw head would be and the longer screws to go through the plywood layers. I should have mentioned a thickness of 3/4" on the plywood disc........nothing less in my mind!

Roger I didn’t read your respond after the first couple of words, as you recommend there that the OP make the turning smaller, well the OP wasn’t asking for that.

Then the plywood disk in this case is OK, but you have to be careful with plywood, as it will easily delaminate and isn’t very safe unless you go with longer screws, here from both sides to hold it, I do have experienced the de-lamination of plywood.

As for safe turning ways , sorry but you haven’t impressed me with your safe turning practises in your posts Roger, so I tend to just not take these very seriously, probably my reason for not reading your whole post/reply

[John Shillabeer]

Thanks Gents for your suggestions and safety warnings.

I have in the past successfully turned discs of this diameter, but only to decorate them. These discs were made by gluing maple shorts together, i.e. less than 1 inch thick. I always use a faceplate for such large diameter and/or off-centre turnings. So far with this disc I have shaped and roughly finished the back, all the while limiting the speed to about 450 rpm. By the way, the wood is very dry sweet chestnut and so is quite light.
So far so good. The disc is now much lighter and running nicely in balance.

I am going to reverse the disc using a big fat glue block and a face plate with a couple of extra long screws into the base as a safety precaution.
Once the inside is finished I will use the big backing plate and locks suggested by Leo and Denis. Then gently turn away all or most of the glue block and maybe resort to some filler for the remnant screw holes.
I hope to be in a position to post a couple of pics like Leo's in a day or two.

[John Shillabeer]

A while back I asked for help turning a large disc on my Nova DVR lathe. I heeded the safety warnings and did the job exclusively with a face plate (no chuck), a big glue block and a large diameter plywood backing disc The large glue block gave me the added security of the larger than usual contact area and was thick enough that I had good access to the back on the headstock side. However what really helped was the backing plate for securing the reversed disc. I cut a groove in it to fit the edge of the disc (now a shallow bowl) and then secured the bowl with hot melt glue and gaffer tape. The result was absolutely firm and did not shiver or shake at all. By the way, If you have never tried gaffer tape I highly recommend it because it is much stronger than e.g. duct tape and leaves no residue. It is expensive but worth having for that special task that crops up now and then

I wish I could say that the result of the turning was as successful as the procedure. I need to learn more about dyes and get more practice using them.

[robert baccus]

Try some Baltic birch plywood for real jobs. Many ply's and as flat as it is strong. The Mercedes of plywood. Try CA and a 3" glueblock on the face--turn and sand the bottom with a dovetail cut for your lathe. Reverse the piece, cut off the glueblock, finish cut and sand the face. Use a soft glueblock here.