Thread: Reverse mounting bowls

Originally Posted by mick59wests

Paul,

thanks very much for the details of what you do. Two things I did not quite understand:
1. When you remount your 'to be' bowl after rough turning and drying, how do you do this to get the spigot or recess round again?
2. How did you get the spigot to be concave? thanks Mick

#1
I inspect every once in a while and when the bowl has turned nice and oval I use a center finder and make a series of lines on the spigot or recess to more or less find a center.

I put the top against the sandpapered faceplate and scoot it around so that a cup center with a sharp point in the center goes into the center of the oval spigot.

The top or rim is held against the faceplate by pressure of the tailstock center. It will be bowed so I make the gap more or less equal between the rim and face plate. The sandpaper provides more friction to drive the bowl and to keep it from sliding out. A good catch will throw it out. I use the cup center with a long point in the center to poke into the marked center of the oval spigot. A cup center can be used if you make a circle a bit larger than the cup center around the center point on the spigot.

I turn the spigot round and establish a flat face for the tops of the jaws to touch. I put a pencil line on the spigot that goes under the center of the #1 jaw. Any time the bowl is removed it goes back in the same position.

#2

The sandpaper is stuck on to my wood circles right out to or a bit past the edge. They mount on the chuck of the late and I run them at 700 RPM. I hold the bowl by the rim and slide the bottom across the edge, rotate the bowl a bit and repeat, taking light cuts each time. Periodically I lay a ruler or scraper across the bottom to see how much of a depression is forming. I make the depression to hold my name and a code number of the bowl, and if known, the kind of timber.

For code I use the last two digits of the year and the number of finished bowl completed that year. 1219 would be the 19th completed bowl or turning done in 2012.

I use a code rather than the date because if it sits in a shop a couple years, a prospective buyer might think there is something wrong with it, even if they like it.

I sell my stuff on consignment, and it a piece doesn't sell in a year or so I bring it back, refinish if scuffed, and take it back for another go the next selling season.

If the above is not clear I can make a few photos.

Paul,

happy new year to you and thank you very much for the explanation. I very much appreciate it.Even for me, that is now clear . So many ways to do things!

cheers

Mick

Shape of spigot? For the Nova 50mm you cut a straight spigot. The graphic shows what can happen if you cut a dovetail.

Spigot size? The jaws are cut from a billet and I assume the width of the cut is 1-2 mm so the jaws must be expanded this much to come back to full circle. For green wood I go about 8mm larger than fully closed to allow for soft wood compression and warping. For dry about 4 mm.

Insert: Do you have a Nova insert or off brand. The off brands can really mess up how true it runs.

Centering: Always leave a divot from the tailstock. This is the last thing removed in the entire turning process. If you cut the divot out when forming the tenon make one of these to fit your chuck and before removing the chuck remark the center. You can also use it for centering your faceplate.
For re-centering the rough turning use a friction chuck and bring the tailstock up to the original divot. I don’t think you can get much closer than that. You will use the same divot for reversing for the final cleanup of the foot.

Jaws: Did you set the jaws correctly? Per instruction leave the screws just a little loose and scroll in. You may even need to bump the jaws with a rubber mallet to get then aligned. Run a thumb nail around them to feel for bumps at the joint. Then tighten the screws.

thanks for the tips on the jaws and marking the centre of the spigot
cheers
Mick