Printable View
Looking for guidance on how to best glue on the rings for a segmented bowl. I'm flattening the glued up rings on a drum sander, and trying to flatten the glued up stack on the lathe, but am still not getting consistently good results. I'm using the tailstock with a 2 x 3/4 ply circle cull to press each ring on as I glue. I still see small areas where the joint isn't as tight as it should be. Any thoughts on a process that would give me consistently good results?
Thanks, Mike
Mike if I understand you correctly, you are looking for a way to clamp multiple semented rings together? I havn't built one yet, and I'm no artist but I have plans in my head for building a vise to do just that.
Step 1: cut 2 circles of 3/4" plywood at least 2" larger than the biggest rings you make.
Step 2: Drill 1/2" holes at 12, 3, 6, & 9 o'clock positions 1" on center from edge of both circles.
Step 3: Cut 4 pieces 1/2" threaded rod at least 2" longer than the tallest bowl you plan to make. If you could find rod with acme threads would be even better.
Step 4: Epoxy or double nut one end of the rods into the four holes on one circle. This will be the base for your vise.
Step 5: Epoxy heavy flat washers over the holes on you other circle. This will be the top of your vice. The washers are to keep your nuts from digging into the wood.
Set your glued rings onto your base, slide top circle onto the rods, screw on 4 nuts and tighten equally. I'm sure there are other better ways, Just what I've had in mind to do.
Mike,
The drum sander should do the job. I'm not sure what you mean by "trying" to flatten the assembly. Is this flattening the top ring each time before adding a new one? For final flattening, I use a 5/4 piece of hardwood lumber (Oak is good) with 80-grit across the face of the ring -- prop it on the tool rest to avoid loss of control.
I'm not a fan of compressing a glue up on the lathe using plywood discs -- ties up the lathe and too many possibilities for off-center. Consider 2 possibilities. (1) Once the glue has set (not cured) use wide mouth clamps with the piece upside down on a plywood plate -- cover with poly film for multiple uses. I think Harbor Freight still has some 7" units for mounting on Pony clamps. Penn State has had even bigger ones. (2) For really wide rings, the same as above except using a cheap bottle jack on the upside down piece with a scrap piece of lumber cut to reach the ceiling or joist above.
Hey, my first post, although I have lurked for a while now. Figured I would jump in head first :)
Segmented bowls are one of my current addictions, and I have tried a lot of techniques to do just what you are trying to do.
The first thing, is to make absolutely certain your rings are actually flat. I fed some rings through a thickness sander a number of times and discovered that snipe can nip a smidgen off the edges, without it being that obvious. Hold a straightedge on the surface, with a strong backlight. If you don't see a gap at all, then clamping is your only issue. The only problems I have had with with glue joints between rings is caused by non-flat rings.
John's advice on using threaded rod through a couple of disks works well. But I prefer to use a bunch of clamps instead. Also, I seldom try to glue up more than two rings at a time. I just don't seem to have the coordination to orient the glue joints and center more than one at a time.
I bought the book "the Art of Segmented Turning" and it is a good book. I have not dove into segmented turning just yet. Still tooling up. Bought Bessy strap clamps for the segmented gluing. Just glancing through, one suggestion he has is to use a pipe clamp (expanding mode) up against the ceiling. (on a joist I asume) Obviously you'd need a plywood caul too.
Lots of good info in the book. Pick it up!
Mike,
Dick probably nailed your problem. An alternative way to flatten rings: Ring is already fairly flat on one side, having been glued up on a flat surface. Using double stick tape, attach the "flat" side to aux. faceplate on regular faceplate on lathe and turn side 2 flat. Then flatten with a sanding board, which is a straight, flat board (I like particle board) with 80 grit paper attached. Put the workpiece (which is in a chuck or on a faceplate) back on lathe and glue on newly flattened side 2. Turn and flatten side one on the lathe. Repeat. Hope that made sense.
Another thought - take smallest possible cuts with your drum sander. Let us know how you solve the problem. Others will want to know.
It is fairly simple to see if the problem is your drum sander or not. Run your rings through the sander. When you get to the point where you would normally glue them onto your workpiece, take a pencil and draw lightly across the face that is to be glued. Make sure you cover the outside edges. That is usually where most of the problems are. Take the ring and makes several passes over a piece of 80 grit sandpaper that has been glued (spray adhesive is great for this) onto a piece of glass. Make sure that the glass is on a smooth surfaced top or is at least thick enough that it will not flex any. After a few passes, look at the surface and if you see any pencil marks left at all, then your drum sander is the problem. If all of the marks are evenly sanded off, then your technique for glueing the rings together is the problem. I personally stopped using my drum sander, as it leaves the surface smooth enough for flat work :D, but not for segmented work. Try using a disc sander and hold the ring up to it and apply even pressure.
For glueing the rings together, a pipe clamp with the pipe attached to the ceiling is simple, effective, cheap, and gives a lot of pressure.
Thanks for all the ideas. Looking at my results, I going to investigate the possibility of snipe on the sander being the root cause. I noted some of the joints improved as I turned the bowl down, consistent with the snipe theory. Clearly I need to come up with a better press scheme as well.
Again, thanks for all the suggestions.
Mike
If your rings are truly flat there is no need for a great deal of pressure when gluing them up. All it realy takes is enough pressure to squeeze the glue from the joint which can be assisted by wiggling the ring while applying pressure and checking alignment. I reccently bought Malcolm Tibbett's DVD's which demonstrate this very well. I suggest getting both his book and videos.
Mike,Quote:
Originally Posted by Mike OToole
One caution when sanding rings on a drum sander - make sure the drum and bed are parallel.
To kill a snipe try using a sled with scrap wood strips on each side. Place the rings between the two strips. The first ring should be set far enough back from the start of the sled to allow the strips to take the first snipe before the ring gets to the drum. The same applies at the rear of the sled, the last ring must clear the drum before the pressure roller drops off the end of the sleds side strips.
Here is one idea for a press. It works well, is collapsible, and is adaptable by using different lengths of PVC pipe.Quote:
Originally Posted by Mike OToole
Cheers