Specific mechanism of spiral catches/runbacks with skew on beading cuts

[Scott H]

I've found a lot of videos with advice on how to do beading cuts with a skew. I am still practicing and getting better, I am trying to internalize what the correct things to do and not to do are. However, I'm struggling to visualize what exactly is occurring when the skew gets kicked back out of the bead and ends up making a spiral back along the workpiece. I feel like if I can get my head around this I will have an easier time than trying to just memorize "do this" and "don't do that." If anyone can help me understand I would appreciate it.

Here is a video I found on youtube of one of these catches if it helps to have an example to refer to.

 

[Mike Davis]

Go in to about 32 minutes.

Allan has another video which explains the catch very well but I didn't see that one right away.
To me he is difficult to watch, not flamboyantly entertaining like the modern vids.
But he has the very best technique and information.

Richard Raffin does a good job of explaining the catch.

 

[Scott H]

Thank you @Mike Davis. The times it happens to me is more like at the 8:25 mark in the Richard Raffan video (time coded link.) I.e., at the start of a beading cut and not when terminating it in a sharp V. I think next what I will probably do is try to replicate it with the lathe off, turning the spindle by hand, and see if it gives me any more insight as to the mechanics of it.

 

[Barry Russell]

The catch results from an unsupported cut. It only takes the bevel slightly losing contact with the wood for the cut to spiral backwards.

 

[Scott H]

@Barry Russell Thank you, I think this is helping narrow down the issue I am having. I am probably not keeping the bevel rubbing when I start the bead consistently enough.

You will have to forgive me as I am doing some maintenance work on the lathe itself for the next day or two so I cannot do any practice runs to report back just yet, I am just going by my memory.

 

[Barry Russell]

Scott, try putting a little extra pressure on the bevel and go slow. The pressure will cause the tool to burnish the wood and make finishing difficult, so this is only for practice.

 

[petebucy4638]

The bevel angle that you chose for your skews can have an impact on catches too. A couple of my skews are ground with very sharp angles, compared to the rest of my skews. They are great for cutting end grain and making small detail cuts, but they are very grabby when it comes to using them for turning beads, or even making planing cuts. They require a lot of attention. Most of my skews are ground to less aggressive angles and are relatively docile in daily use. Just a thought.

 

[peltona]

A good rule of thumb is watch the handle angle as it relates to the spindle (picture top view). As you are standing at the lathe with the headstock to the left, lets call that zero degrees and the tailstock 180 degrees. As you turn beads to the left, your skew handle should stay in the right half or 90-180 degrees. Opposite for turning right sided beads. I like the advise above of turning off your lathe and turn the piece by hand. I'll often chuck a piece that already has the bead I intend to turn just so I can follow along to get an idea of tool rest height, handle angles, handle twist rates and where about my skew will be when it finishes, especially when its been a while since I've practiced with the skew. Keeping point engaged and watching the wood come off it will help you keep the sweep, twist, handle raise ratios correct for your setup while minimizing bevel loss (spiral).