Longworth chuck

Rob Keeble

Member
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12,633
Location
GTA Ontario Canada
Hi All

I started on a Longworth Chuck to suite my lathe which only has a 13 inch diameter swing ability over the bed.

So I am at the stage of getting my arcs cut out in the two discs of plywood that i am to use for the chuck.

Here is my issue that i have been pondering all weekend. I have made a circle routing jig for my PC router to be able to cut the arcs.

The arcs pivot point due to size of disc 13" and the size of my faceplate 2.5" means that when i rout the arc the pivot point for the next arc is in the path and will disappear.

I need some wisdom on how to overcome this. I have come up with some crazy methods but they are too way out. I am sure the wisdom here with slap me silly with a why didnt I think of that.

So i need some spinny help if i am to get this chuck finished.

Thanks:thumb:
 
Rob, what happens if you move the pivot points in (or out) a 1/4" to 1/2" from the center? I don't think a slight change like that would change the operation of the "jaws" significantly.

Or another approach might be to change the number of arcs...if you're planning on four, make five or six.
 
:rolleyes: I just finished another chuck last week and the starting points did not intersect with each other. I followed other instructions on it and it just came out this way. You can see the marks. It is 11 1/2" dia. My lathe is a Jet 1220, just makes it.:huh:
 

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Rob,
I may not be any help, but when I made mine, I made the pivot points half way between the inner most circle and the outer most... i.e., I drew a circle that would be the size of my faceplate (I made my face plate from wood (a 4" circle then added a 2 3/4 piece onto to that so I can mount my longworth in a chuck rather than using my face plate... I only have one small one and don't want to tie it up permanently, and it doesn't work to take them on and off the longworth..)).. my lathe is a 1442 Jet, so my longworth is 13 7/8 inches.. it just clears the ways and I put the outer circle at about 13 inches. I didn't have a jig and my router is a cheapy from Sears and so is my table, so I actually free handed the arcs... my arcs are relatively smooth, but not like they would be on a jig and my router bit was a little dull... I got a lot of smoke.

It works great, but doesn't look anywhere as neat at John's
 
Thanks guys I knew I could count on ya all for a fix. Sometimes the way i think has me worried.:rofl: I like the aspect that most of you who have replied have more than 4 points in your chuck. I was wondering about that but then got tunnel vision following the plan i have. I need to set myself free and use my own intuition. Well thats one thing off my mind and solved.

Thanks again.:thumb:
 
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