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turnerted
13th April 2013, 06:09 PM
G'day
At Turnfest I watched a demo by Len Mengal on making eccentric bowls and decided I would like to have a go at one. Len used an Escolin chuck and various adaptors which I don't have ,so I decided there should be a way to do it without all the expensive fittings.
The following describes how I did it, But first a word of warning, this is potentially dangerous and should not be attempted unless you have a good heavy lathe preferably bolted down. It would also be risky unless you have variable speed,either mechanical or EVS.
I mounted a blank of jacaranda on a screw chuck and trued it all up then marked 1/4 the way down. I then shaped and sanded the bottom of the bowl from the line down to the foot .I then hotmelt glued on a tenon which had been preheated in the microwave oven. I then put the whole thing in the freezer to harden the glue.
I now trued up the tennon then turned the blank over and turned about 100 wide section down to meet the bottom side. I sanded this section then decided to do a bit of embelishing so I used my Sorby texturing tool then applied Feast Watson Prooftint then acrylic gold paint. When this was dry, I sanded off the surface acrylic to just leave the gold in the indents.
I now turned up a bit of scrap which was about 100mm long and aproximatly the diameter of the foot and cut a tennon on it.I now cut off the tennon on my table saw with the blade set at 7 degrees,the offset that Len recomended.I used a digital angle gauge to set the saw up, but a mitre gauge and protractor would work. continued

Skew ChiDAMN!!
13th April 2013, 06:30 PM
(Watching with interest... & hoping for pix! :D)

wheelinround
13th April 2013, 06:38 PM
:iagree:

hughie
13th April 2013, 06:41 PM
Jeez Ted I got an old lathe that'll do it for you, don't need no fancy gizmo's :U

turnerted
13th April 2013, 06:41 PM
I now mounted the cut off tennon in a chuck and used the live centre to find the centre on the angled side , the tennon was then removed from the chuck and and a hole drilled through it which was just slightly smaller diameter than a 3 inch nail . The hole was drilled aproximatly at rightangles to the angled face.
I now put the part turned bowl in the microwave oven and heated it up until I could remove the tennon then remounted the still hot bowl using the screw chuck.I heated up the offset tennon for about 30 seconds , put a good glob of hotmelt glue on it and using the nail through the hole in the tennon,I lined it up with a reference point I had made made on the foot of the bowl. I then used the live centre with the point removed to hold the tennon in position . The nail goes up the hole in the live centre. I then left it overnight.
I now mounted the bowl on the offset tennon and gave it a good thump to make sure the gluejoint wasn't going to break, stood clear then slowly started up the lathe. Everything went fine and even though I was running the lathe faster than I would normally, I had no problems with vibration.
To be continued. It's dinnertime. Ted

turnerted
14th April 2013, 10:14 AM
The only difficult thing about hollowing out the bowl, is cutting the edge cleanly because there is about 10mm variation between the high and the low side ,hence the need to run the lathe fast. By starting hollowing from the centre, and gradually increasing the diameter, I was able to get a feel for it and end up with a crisp edge.Once I was down far enough that I was touching all the way round, it was straight forward.The deepest part of the bowl is next to the narrowest part of the rim and I needed to check frequently as I got deeper to make sure I didn't go through the bottom.
Sanding was pretty straight forward using a power sanding cone .
I put several coats of DO on, leaving overnight between coats.I buffed on the lathe between coats. My lathe will only go down to about 200rpm so the hands got a good workout when buffing the parts turned on the original centre.
None of the usual methods of removing the tennon will work with a bowl like this.Len uses Cole jaws with longer bolts and and notch shaped plastic grippers to hold his bowls, supplied by Vermec.I just zapped the bowl in the microwave until the tennon could be removed. I then scraped off as much residual glue as possible with a flat chisel and cleaned it up wih turps . I then mounted a jacobs chuck with the power sanding cone in the headstock and sanded the foot by just by holding the bowl up to it.
One thing I forgot to mention, there may be a need to consider the orientation of the grain pattern on the top of the bowl . continued

turnerted
14th April 2013, 10:44 AM
When glueing on the offset tennon,consider that the top of the bowl above the thicker side of tennon will be turned off first and will be the narrow rim side of the bowl so you don't want to turn off any feature pattern . One of the pictures shows the reference marks on the bowl bottom and tennon.
The following pictures show the sequential steps. The last two pictures are of a previous cypress bowl .
The jacaranda bowl is 270mmx55mm and the cypress 250mmx70.
I am pretty happy with the bowl shapes although I have more work to do on perfecting the rim embelishment.
Hope you find this interesting.
Ted

turnerted
14th April 2013, 10:49 AM
For reasons which escape me, the pictures did not load in order, but I'me sure you'll work it out.Also the final shot of the jacaranda was missing.
Ted

DaveTTC
14th April 2013, 04:23 PM
Great read, would have been even better if you had inserted pictures at each step of the way or had a video link.

Thanks for all the effort you went to to write this up. Hope to see more from you in the future

Regards

powderpost
14th April 2013, 08:57 PM
Excellent job Ted, just proves you didn,t go to sleep at all. :)
Jim