Four Jaw Wood Turning Scroll Chuck Comparison?

[Tom Albrecht]

Sorry if I am revisiting an old subject--

I have a ONEWAY Stronghold, and I recently bought an EASY Chuck.

Yesterday when I put the screw thread into the EASY, I noticed some wobble at the far end. I checked my ONEWAY with their screw, and it had very minimal, if any, wobble.

Then I tested a little bit. I installed a short length of 1/2" hardened drill rod into each chuck and checked for run-out with a dial gauge. The ONEWAY was running out 5/1000s 2 1/2" out from the jaw face. The EASY was running out 13/1000's at the same 2 1/2" mark. (13/1000's is visible without a dial gauge.)

I know these are wood turning chucks, so I am guessing they are not made up to the same requirements as a metal spinning machine wood need, but should I expect greater accuracy from the EASY?

 

[Dennis J Gooding]

Chuck runout

Tom, it turns out that with at least some chucks there is enough play in the chuck jaws relative to the chuck body that you can get significant runout depending on the position of the jaws when the mounting screws are being tightened. In these cases, you may be able to reduce the runout by clamping the slightly loosened jaws onto a round object held centered by the tail stock and then re-tightening the jaws. For example, I had a problem aligning a set of pin jaws in a Vicmarc chuck. My solution was to loosely clamp the pin jaws onto the half-inch nose of my OneWay live center and then re-tightening the screws. Simply tightening the jaws onto a free-floating round object will force the jaws into a circle but will not guarantee that the circle is centered on the spindle axis. Small amounts of runout are of concern only if you want to change your mounting during the course of a turning.

 

[Bill Boehme]

I would repeat each test several times because the process of clamping down on the drill rod could account for significant shift in runout. I don't think that what you see is really significant. I would worry if the chuck body itself wasn't running true because that could introduce vibration. Also I would be concerned if the jaws could move relative to the body while clamped down on a piece of wood.

It is important to recognize that the wood you are turning will be turned true with respect to the spindle axis of rotation and not the jaw orientation. However, the alignment error that you point out is the reason that the tenon or rabbet orientation should be marked on the wood including the jaw number in the event that you remove and then reinstall the piece onto the chuck. And, of course, using the same chuck would be important.

 

[Tom Albrecht]

thanks

Thanks guys, that is what I suspected, but just needed confirmation.

 

[Odie]

Tom......Instead of 2 1/2" out from the jaws, you also might want to try the measurement as close to the jaws as you can get with your dial indicator......just to check the consistency of the measurements.
ko

 

[Raul McCai]

The ONEWAY was running out 5/1000s 2 1/2" out from the jaw face. The EASY was running out 13/1000's at the same 2 1/2" mark. (13/1000's is visible without a dial gauge.)

0.013" is a fair bit of run out Is that TIR or 0.013" on just one side?

I know these are wood turning chucks, so I am guessing they are not made up to the same requirements as a metal spinning machine wood need, but should I expect greater accuracy from the EASY?

Indubitably they are not. I have what must be an 85 year old Elgin lathe ( circa 1930), with 4 chucks of about the same age. The level of precision in my four chucks is astonishing. I can chuck a piece in my three jaw inside chuck and also on my three jaw outside chucks, turn it inside and out face it, then flip it use the face of the chuck as a reference & just close the jaws and my work will settle in closer than 0.005 TIR diametrically and faces are coplanar within 0.0007" to 0.001" ( won't get that from the Grizzly lathes).

The four jaws of the metal chucks as you know all adjust independently. But the reference face of the chucks is flawless.
It's this model with the original maple bench and legs and even the drawer. I recently replaced the motor and switch.

 

[Tom Albrecht]

I am not sure what "TIR" is, but that .013 was at the same spot on each revolution of the round bar.

 

[Raul McCai]

I am not sure what "TIR" is,

Total Indicator Readout.
Also expressed as Total Indicator Runout

Here's a write up
http://www.engineersedge.com/wwwboard/messages/82.html

 

[john lucas]

What I usually do when I change jaws is to leave the screws just a hair loose. Close the jaws so they all touch and then tighten the screws. I haven't checked the accuracy in a while but they seem to run perfectly true when I do this. I'm going out to the shop to clean a couple of chucks so I'll try it and check them with my dial indicator to see what if any the runout is.

 

[Tom Albrecht]

What I usually do when I change jaws is to leave the screws just a hair loose. Close the jaws so they all touch and then tighten the screws. I haven't checked the accuracy in a while but they seem to run perfectly true when I do this. I'm going out to the shop to clean a couple of chucks so I'll try it and check them with my dial indicator to see what if any the runout is.

John, I think your method of tightening the screws after they are touching was originally part of the sequence in the Nova Chuck instructions. I no longer use a Nova, but I follow that process with my ONEWAYs. The EASY chuck jaws don't screw down, they are all directly threaded into the scroll.

I'll be curious to see your results.

 

[Bill Boehme]

What I usually do when I change jaws is to leave the screws just a hair loose. Close the jaws so they all touch and then tighten the screws. I haven't checked the accuracy in a while but they seem to run perfectly true when I do this. I'm going out to the shop to clean a couple of chucks so I'll try it and check them with my dial indicator to see what if any the runout is.

I've done that too but then after studying the way that Oneway and Vicmarc jaws attach to the chuck I realized my folly. The only purpose of the screws on Oneway and Vicmarc chucks is to serve as fasteners ... that's it. Alignment is provided by a boss on the inner jaws (that's Oneway's term for the part that is the interface between the outer jaws and the scroll. You can prove it to yourself by removing the screws to see how much radial play there is between the inner and outer jaws. Remove the inner jaws to get a better feel for it since the slop in the scroll can be misleading.

Even if there were not an alignment boss, the flat head cap screws tend to be self centering to the same position regardless of how you might try to reposition the jaws.