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Longworth chuck

Not having well-lined and deep pockets, I built myself a Longworth chuck so that I could finish the bottoms of several bowls that are otherwise completely turned and finished.

I made a couple mistakes.

1) It is a good idea to be amazingly precise when marking the pivot hole for the arcs. The thing will work if you are merely incredibly close ... but amazing would be better. Be careful marking these holes and even more careful drilling them. THEY ARE the source of the accuracy (or not) of this chuck. The chuck center only exists as a means of locating these holes, the holes themselves locate the important parts.

2) Do not fasten the stupid backing plate to the stupid face plate block with a stupid screw through the stupid center while the stupid glue dries. You will need to drill the center later before separating the halves. It can get ugly. I used a hardened drywall screw. It got ugly. Mine works, but the hole I ended up making is somewhat elliptical and this results in my having to give it several 'alignment whacks' to get it to run true. I need to make another. Space multiple counter sinked screws outward of the center by an inch or two and you should be fine.

Do not hesitate to route it for 8 slots instead of the 4 slots in the instructions below. However, no guessing ... don't rely on a reference angle, use a compass to bisect the original angles. This is one step that I got right.

Start here.

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Reply to
Anonymous
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There are a number of ways to reverse chuck work which do not require the precision and complexity of a longworth chuck. Also, many of them work for natural edge bowls and hollow forms where the longworth doesn't.

Bill

An> Not having well-lined and deep pockets, I built myself a Longworth chuck

Reply to
Bill Rubenstein

If you have a tailstock and a chuck, here is the method I use:

Turn the bottom side of the bowl with a faceplate or screw chuck on the top of the bowl. Make a flat bottom for the bowl. Cut a mortise for the chuck jaws to fit inside. At the center of the bottom leave a small round stub about 1/2" diameter. This will be at the flattened bottom level and not as far in as the mortise. In the center of the stub, turn a tiny hole for your tail center using a sharp pointed scraper or skew. Remove the bowl.

Mount your chuck. Turn the bowl around and hollow the inside. Sand. Unchuck the bowl.

Prepare a dry, endgrain round wood block to be held by your chuck jaws. The block should be long enough to reach to the bottom of your deepest bowl. Glue on a mouse pad or similar thin rubber. This block holds fine grit velcro sandpaper (finer than your finish grit) and will provide the drive for the bowl.

Reverse mount your bowl by holding it against the block and pulling up your tailstock. Align it with the hole in the stub and tighten your tailstock screw. Spin the lathe at low speed. If it looks like the bowl is not vibrating, you are good to go. Otherwise, take a sharp knife edge (like a skew), put it at lathe center height on your toolrest and hold it perpendicular to the bottom of the bowl and at the edge of the flat bottom. Rotate the bowl by hand. Adjust the knife edge until it aligns with the outside of the swing of the bottom. This point on the rotation of the bowl should then be moved back (to do so, unscrew the tailstock and push it back slightly and retighten).

Once mounted true, use a gouge or round scraper to cut out the grip marks from the sides of the mortise and blend the curve into the recess. Pull back the tailstock and take the bowl out.

Carefully chisel off the stub. Using a soft pad sander of small diameter in a small, handheld drill, smooth up the recess of the bowl using three grits of sandpaper. Since it is face grain, it goes quickly.

I made a longworth chuck and found it tedious. Plus, it doesn't work for natural edge bowls.

Derek

Reply to
Derek Hartzell

I will also add mark your arcs "DARKLY" and make sure they don't cross the path of your pivot holes. Don't ask how I know this can be done.

Reply to
vernon

after making a longworth chuck for my mini lathe and using it, I eventually decided that a simple flat backing plate with some carpet on it was about as useful - hold the bowl to the backing plate with the tailstock, finish off the foot except for a small nubbin that the tailstock pushes on, stop the lathe, carve off the nubbin and sand smooth - it's cheaper and easier, and it won't release your work to go rolling around the floor nearly as often.

Reply to
william_b_noble

I made a Longworth chuck last year and used it a few times. I have a cole jaw set that I use occationally also but with larger turnings decided I wanted something that could hold a greater diameter than the commercially made cole jaws. I made a prototype longworth just a bit larger than my cole jaws just to see if I could.

For the most part I make a jam chuck and/or use double sided tape to reverse turn a piece but a longworth can provide a way of reversing bowls that are too large to fit between centers on my lathe.

PS: The l> Not having well-lined and deep pockets, I built myself a Longworth chuck

Reply to
william kossack

Hi William

Depend> I made a Longworth chuck last year and used it a few times. I have a

Reply to
Leo Van Der Loo

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