Longworth chuck Mk1

[orraloon]

Hi everyone,
Had a first stab at a longworth chuck so decided to share the experience and ask advice. The first pic shows the backing block in the nova. While this seems to work reasonably ok from the limited trials I have done would it be better on a faceplate.
Second pic is the chuck made of particle board with a front plate from laminated flooring off cut. The whole thing cost $15 for hardware.
Third pic is with a bowl spining. It centers reasonably well using the tail stock to line up.
Last pic: As for grip I found the sink stoppers a bit soft and had the work fly off when using a scraper. To firm up the rubber stoppers I filled them with silicone and will report back when it has dried and I have another go.

Regards
John

[Big Shed]

Looks good orraloon, I have a feeling you been watching nikki too much. Laminated flooring indeed.

If the silicone trick doesn't work, the rubber blocks are available as spare parts from Teknatool.

[hughie]

,



Last pic: As for grip I found the sink stoppers a bit soft and had the work fly off when using a scraper. To firm up the rubber stoppers I filled them with silicone and will report back when it has dried and I have another go.



John,
Silicone may not be rigid enough. If not try cutting some plywood discs that fit neatly into the sink plugs. This will considerably lower the flexiblility.

I did this on mine and have had no trouble. Other wise top effort, no reason why it should not serve you well.

[TePe]

Hi John, when making this type of chuck over here we use demi-john stoppers from the wine brewing industry. Size is about 1 1/2" high x 1 1/4" dia top x 1" dia base, and solid hard rubber with a hole already through the centre for the airlock. We can get ours from a Home Brew Centre, and are not expensive.

Don't know if you can get similar your side of the pond.

[orraloon]

Thanks everyone for the feedback. The silicone firmed up the stoppers but left a bit of flex also. The harder the wing nuts are done up the firmer they get. I was successful in cleaning up the base of a platter with tools and sandpaper. I was very careful with the tools. There is a bit of wobble so mk2 will be on a faceplate and have 6 stoppers. As it stands I am confident doing any sanding on it and that is ok for most things. I have a couple of rough turnings that have dried with the base too warped to remount so tools have to be used to true them up. Mark 2 will be aimed at them. My thanks to Niki for the laminate flooring idea. It would be an interesting thread to see just what can be made from laminate flooring.

Regards
John

[joe greiner]

Top effort, John. I see old newspapers are your friends, too.

Six buttons will also work better for thin-walled bowls. I learned the hard way that 4 buttons put too much concentrated force on thin walls.

Some suggestions:
* Before tightening the buttons, center the bowl with the tailstock, and give it a spin or two.
* Tighten the buttons in across-the-diameter sequence, not along the perimeter. Similar to tightening car wheel lug nuts in a star pattern to maintain centering.
* Place a couple wraps of duct tape or filament tape across the bowl, shy of the working area, with the free ends taped to the back of the back plate (i.e. the headstock side). A staple or two may also help to keep the tape attached, but usually not needed.
* I added some half-holes on the perimeter of the back disk to facilitate one-handed tightening of the disks while holding the bowl in position with the other; pic 3 of this: http://www.woodworkforums.ubeaut.com.au/showthread.php?t=52167

Joe

[littlebuddha]

Six buttons
I agree that six is better than 4, made the for and found that a 6 would be much better then found that making the 6 i got it nicked by the father in law, now have to make another.
The Longworth fits straight to my spindle thread. the bottons are dowel drilled for the bolts and then small walking stick rubbers.
The 2 ply spanners in the pic are what i use for finding the sizes for diff chuck jaws when doing the spigots, largest and smallest for each set off jaws.

http://www.shapewood.co.uk

[orraloon]

Thanks for the info on the 6 way joe

[joe greiner]

Another good thing about 6 versus 4, is that it's easier to lay out a hexagon than a square - using compass alone.

Great idea about the spanners, Buddha. Lots easier than consulting tables of measurements etc. Might even use a four-bladed affair: inside small, inside large, outside small, outside large. One piece for each set of jaws. Or something like that.

[Well, this is the general idea. Screen shot from CAD. But the large gauge would probably be better with the calipers cut on each face of a square stick.]

Joe

[joe greiner]

Another good thing about 6 versus 4, is that it's easier to lay out a hexagon than a square - using compass alone.

Great idea about the spanners, Buddha. Lots easier than consulting tables of measurements etc. Might even use a four-bladed affair: inside small, inside large, outside small, outside large. One piece for each set of jaws. Or something like that.

[Well, this is the general idea. Screen shot from CAD. But the large gauge would probably be better with the calipers cut on each face of a square stick.]

Joe

Too late to edit this (>24 hours). Improved caliper design in process. New thread in a day or two, with working title of "Chuck Jaws Calipers."

Joe

[littlebuddha]

Hi Joe will keep my eyes peeled see how you do, interesting idea. What i like about the spanner gauge is that it gives me the basic size for, whichever jaws and then i can put the dovetail in, and being rounded at the start can use while the lathe is going saves on turning on and off all the time. So you have a lot to turn me away from them:D LB..

[joe greiner]

Hi Buddha. I'll be making version 4 today, and I hope that's the end of it. Too many "features" to include operation at speed, so I don't expect to convert you. At least I'm at the simplification stage.

Joe