Oneway jaws

Hi Robert, from this Leo, :

What Leo has difficulty comprehending is that the jaws he describes damage the wood, precisely because the contact area is _less_ than the smooth jaws.

Strength of the wood is measured as a resistance to a force per unit of area. Total Force = Force/unit * number of units. Stands to reason that if you have knife ridges as your primary contact points, there is a tremendous amount of force on a small area, which is why they penetrate and deform the fibers. The smooth jaws provide a greater contact area, depress the resiliant surface rather than sever the fiber, and since the total force is a multiple, they require less crank on your tightening device. All you need is snug, not grip.

If you can live with mangled wood fine and dandy. Crank down and chew things up. But when you look at what you've done afterward, notice that as the fibers are pushed away by the ridges, they also push you out of register with the face of the jaws, denying you the resistance to deformation perpendicular to the axis of rotation which is what prevents a catch from dismounting the piece. The dovetail draws the wood in toward itself as it is expanded or contracted, making that contact firm and sure.

People who grab things with serrated jaws are the ones who complain about having to re-true the outside after reversing, because they have difficulty getting a full seating. They are the ones who tell you you have to "settle" for a certain degree of error. People who use smooth dovetails can mount as true as the shoulder they have made for an outside grip, or the interior shoulder they have made for an inside grip. They can take the piece off, and if dissatisfied, re-mount and trim where the design does not please, because their hold is _still_ circular and undamaged, available for use. They don't have to try and make the serrations fit into old grooves, or, after realizing that's not possible, try to get a whole fresh area to crunch.

Additional advantage to inside dovetails, if you're trying for depth on a bowl made with the outside of a log as the bottom, is that you need only cut away enough to allow entry for your expansion jaws. Gives you as much extra depth as the length of the tenon you would have made, only to turn away later. With an external dovetail you don't have to trim away ugly compressed and chewed wood if you can make the groove part of your design.

Take a careful look at

Look at 5:00 o'clock and you will see the artifact from the interior hold, as yet unsanded. The artifact of the exterior hold, because this piece was done as a demo, are around 2:00 o'clock. No vacuum chucks, no cole jaws, just a quick sandpaper cleanup and then a finish.

Hi All

Anyone who wants to see the mangled crushed and chewed up wood have a look at the link provided.

A larger than 20" bowl turned without tailstock support on a Oneway chuck, and as several turners have tried to tell a certain person that there is NO Mangled or Crushed or Chewed up wood, it does not seem to sink in, so for all who would like to assert themselves of the facts without the BS, have a look.

Have fun and take care Leo Van Der Loo

It could be that you are BOTH right. It is undeniably true that a set of round jaws that do not fit the wood will hold poorly, with high contact pressure at the points of contact. One-way solves this problem by a set of "wavy" jaws which fit better over a range of sizes. On the other hand, if the spigot or recess is matched to the diameter of the jaws, contact is spread over a large area, so there is less damage to the wood than the "wavy" jaws would produce.

I started with the One-way chuck, and I like the way it holds. I couldn't care less about the jaw marks, 'cause I can always clean that up afterwards using Cole jaws, a jam chuck or a vacuum chuck. (I'm not a production turner, though.)

Hi Leo (The Other One)

That is exactly what I said Leo.

By cutting the exact spigot or recess, you have the complete surface holding, but then you need more jaw sets for some flexibility, in the sizes you can make them. Also said that one way of holding does not fit all and every possible situation. However I do feel that the Oneway chuck and jaws do give me the most flexible secure holding system. As for the jaw marks on wet wood, there is little, and with some care on dry wood, there is none. Not only that but I very very seldom do not change the foot to a more pleasing shape (my opinion OK) and turn the held surface away.

Have fun and take care Leo Van Der Loo

Leo's using some of that non-Euclidian geometry, I guess.

Straight line meets a circle at one point only. If that straight line is interrupted in a second dimension, as it is with serrations, only the sharp points meet. Such can only begin to contact as much area as a smooth circular jaw after the serrations are embedded. Further, any curve, regardless the difference in radii, is a better fit to another curve than a straight line. Given the flexibility of wood, a reasonably close fit will get a tremendous amount of metal in contact within springback limit.

Lots of good iron out there if you know how to use it. Some is getting downright inexpensive, without, it would appear, the drawbacks we expect from paying less. Just remember when you choose your chuck, and your mount when turning, that you don't have to have a certain kind of jaw to hold your work securely, you have to have a concept of what constitutes a secure hold. A good hold has parallel and perpendicular aspects, and just as the M/T wood joint it imitates, the wood held by the sides of the tenon is subject to forces which are countered by the shoulder. Choose your jaws to provide the most easily and repeatably certain way of doing this - wedge 'em.

Ordered my 75mm set from Lee Valley with my birthday gift card. Couldn't convince the spouse that I should be able to tap the family resources while that card awaited some special purpose. As I look at the design, I can see that they will be a great choice for tenon holds on smaller stock like branch turnings, which don't approach the size to be held in the 100mm set. May see more use there than with bowls. Good broad contact areas for stability. Gotta love the self-adjusting feature that comes only with smooth metal making a best-fit average rather than forcing the issue by digging in early, too....

Well Leo, your way of thinking is certainly good enough for me. I have been to the website, seen your work, and read you well thought out and intelligent posts here for far too long to doubt what you are saying about Oneway chucks, (or Oneway anything for that matter!) especially since I don't own any Oneway tools.

I especially agree that we don't have any one device to hold everything we can imagine. I still use faceplates, even thought I have two Vicmarc 120s with 3 different jaw sets. One chuck is configured one way (no pun intended) and one is configured another way depending on what I am doing.

No need to duck... I am certainly glad to hear your opinion.

Even though I wouldn't trade my Vics for any Oneway.... ;^)

Robert