Longworth chuck

[Les Symonds]

Amongst the bits and bobs that came with my new lathe, was a Longworth chuck. Home made and seemingly quite accurate, it looks like it could come in quite handy, given the larger diameters that I'm going to be able to turn.

I'm wondering whether or not any members have experience of them and how they perform. My main concern is that it 'grabs' the wood sufficiently.





For those (like me) who haven't come across these before, it's made from 2 discs of plywood with spiral slots milled into them. one disc has slots radiating in a clockwise fashion, the other goes anti-clockwise. When the discs are superimposed upon each other, at some point, each pair of slots reveals a gap right through the chuck into which is placed a set-screw with a rubber button on it and between the 8 of them, they form a perfect circle, just like the buttons on a normal bowl-reversing chuck. Adjusting the chuck, by revolving the discs one way or the other, results in the buttons making a larger, or smaller circle. This particular one fits bowls from just 4" diameter, right up to 15" diameter....can't wait to try it out!


Les

[Bryan Milham]

Les,

O made one some years ago and still use it quite happily.

It main purpose is to clean up the foot after you've cut off the tenon (etc.)

Just keep the speed down and cut gently.

[Les Symonds]

Somehow, Bryan, I had a sneaking suspicion that you'd have one! So....do you place washers on the screws, in-between the two wooden discs? Mine is quite difficult to adjust; there's just too much friction between the discs to enable them to slide upon each other and it's quite a task to adjust it. I was toying with the idea of opening it up and putting washers in there to ease things a little.

Les

[Bryan Milham]

Les,

Somewhere in this forum I posted a 'How to make', but not sure where or how long ago.

Mine is only a 6 groove one, I see yours is 8. Mine can be hard to get moving sometimes, I found it best to really slacken the through bolts. With 8 you'll definitely have to loosen them to rotate it easily.

[bodrighywood]

I haven't used these myself but looking at yours would it better if you had longer rubber studs? I have seen others and they seemed to have them at least twice as long. Ignore me if I am talking rubbish

Pete

[Les Symonds]

Hi Pete (there you are....I didn't ignore you!) As it happens, the rubber buttons are somewhat better than the ones fitted to my commercially-made chuck. They're longer and they're a larger diameter. Also, they are stepped from a smaller diameter at the base, increasing diameter in the middle, and then again at the top. it's probably the overall size of the chuck that makes the buttons look comparatively small!

Les

[malcy]

Hi Les. I have a home made one of these. They can be tight to adjust sometimes, especially if the bolts holding the rubber buttons stick in one disc and not the other, causing them to tip in one direction. It is therefore necessary to keep these at right angles to the surface for easy adjustment. When you have adjusted the chuck to the required diameter, it is essential that the discs are locked tightly together to stop them slipping. Again only use light cuts when turning and use relatively low speeds. I frequently use this for centring rings when assembling segmented pieces, so they have more than one use. You can easily make them to whatever size you want, which is an advantage over Cole jaws (bowl reversing jaws). Malcolm.

[The Bowler Hatted Turner]

Hi Les,
          try a spray on dry lubricant, something like the silicone spray from Halfords, that's what I use when I need it all to slide.
Regards
John

[hughie]

Washers under the rubber will over come the sticking bit. Also keep an eye out in the hardware for different rubber bungs and stoppers as its handy to a variety of these for changing shapes.