Longworth Chuck – Done Enough

Returning to the shop after being sick for a week is a great feeling. After catching up with the guys, we dove right into our projects. Indy is working on kitchen chairs, while Brad and I finished up the Longworth chuck.

Truing the Longworth chuck on the lathe.
Truing the Longworth chuck on the lathe.

First order of business was to put it on the lathe and true it up. Brad was running the lathe for the evening with a full face mask as we are cutting plywood. We don’t typically turn any plywood so we weren’t quite sure what to expect. Add to that, even on the slowest speed setting at 150 RPM, the outside of the chuck was moving quite fast.  I initially suggested he try the Easy Wood Tool, he hesitated and grabbed a small bowl gouge. He took a few light passes and quickly concluded he wasn’t comfortable with it. I then suggested a large domed scrapper, he hesitated again but gave it a shot. This worked better than either of us expected, although it was slow going, at least it was safe. It left a reasonably nice finish on the Baltic birch plywood. As you can see in the picture, it was even taking curls off not just saw dust. But we had nearly a quarter inch of inconsistency to resolve and it would have taken too long. He finally grabbed the Easy Wood Tool. I suggested he not work from the edge as he did with the scrapper but work from the side. This would remove the undulating motion he was getting from it being out of round. It worked great, the plywood bits were flying off quite fast. We quickly learned to work from each edge toward the center as it cut down on the tear-out we were experiencing. This got things true very quickly, but left it a bit rough. Back to the scrapper, he rounded the corners which cleared up most of the tear-out that we had. He wanted to give the small bowl gouge another try. This worked much better now and left a nice finish, although I think it was about the same as the scrapper.

I grabbed some 150 grit sand paper and touched up the edge. Then I reversed the lathe and with it running backward I removed the rest of the rolled over fibers. Even on the slowest setting the sand paper heated up very quick. So take it slow as even 10 seconds of pressure was to hot to hold.

Drilling finger holes in the back face of the chuck.
Drilling finger holes in the back face of the chuck.

While it was still on the lathe, I marked a line from the edge to where the finger holes would go. It was simple on the lathe to get it consistent. I then marked  approximately half way between each of the spiral grooves on the line to give me a center mark to drill.  After disassembling the chuck I drilled 13/16″ holes through each face individually.  Of course, I left the face plate on as you can never get it back on exactly how it was before you take it off. Why that size? Because it’s a size we don’t typically use so the bit would be sharp and we wouldn’t be dulling the more commonly used Forstner bits. Why the spacing for the finger holes? Well it just looked good, which ended up being half way between each of the spirals.

Next up was a bit of hand sanding on each side of the holes and spirals, then hit the inside faces with some 150 grit sand paper on a random orbit sander. I had to be careful as it would have been really easy to sand through the top layer of the plywood which would have been a bit too aggressive. I also slightly rounded the inside edges of the outer circle.

Bowl back on the chuck and ready for initial testing.
Bowl back on the chuck and ready for initial testing.

We didn’t have a nylon washer around at the time of assembly, so we grabbed a regular one and put it between the two faces. This ended up being a good thing as it gave us a bit more distance between the faces. After assembling the rest of the chuck, we put it back on the lathe. A couple of tests by both Brad and I leave us quite pleased with how well it functions, so I grabbed the bouncing bowl and put it into the jaws. We used the tail-stock without a center in it to help hold the bowl tight. This allowed easy adjustment of the faces with the finger holes. You don’t have to tighten the wing nuts to hard for it to start squatting the rubber nicely against the bowl. A quick final round of tightening to verify they are all even and backing off the tail stock. We both step away from the line of fire and turn the lathe on slow. All is good, in fact so good I slowly turned the lathe up in speed. Once I hit about 850 RPM I was certain I could have gone higher but there was no need. We turned the lathe off and checked all the bits and pieces, nothing moved.

While the chuck is not actually complete, its done enough to use! Back to working on the bouncing bowl. I grabbed a chunk of scrap 2x pine stock and cut it out on the band saw to roughly round. With an excess of yellow glue I used the lathe to clamp the block onto the bottom of the bowl. Finally we are back to a point of actually being able to work on the bowl, so that is what we’ll do next time.

I still would like to put some finish on it and wax it, but its totally usable.

Bouncing bowl with new glue block clamped and drying.
Bouncing bowl with new glue block clamped and drying.

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