Oneway Jaws (Talon and Stronghold) - Perfect Circle

[Edward Kerslake]

I'm in the process of designing some carriers for my jaws. I like to store my jaws in a tray, off the body of the chuck and for those dovetail jaws, at the perfect circle diameter.
That perfect circle is the ideal dimension of the tenon when gripping,

Does anyone know what these diameters are? Oneway doesn't list them (Vicmarc does in contrast)
I have a lot of jaws and if anyone has measurements to share, that would be great!

Thanks

 

[Holmes Anderson]

Maybe I don't understand what dimension you need but https://oneway.ca/products-category/chucks

 

[Edward Kerslake]

Thanks for trying but I have that info ;-*
If you look at the table, Oneway mentions the 'design diameter' (lower left of page)
That's the number I am looking for. It's the amount that the jaws have to be opened in order to grip a perfect circle (with the dovetail jaws)
For most manufacturers (e.g. Axminster) that's about 1/8" because they make the jaws from one billet and then slice it across to make the 4 jaws. I don't believe Oneway does this and so I am not sure.
I can eyeball, but if I could get the actual, that would be preferred
Thanks
E

 

[hughie]

For me the answer was more chucks, as I found chnaging jaws tedious and I often dropped the screw into the sawdust. OK now I have a chuck cupboard

 

[Don Wattenhofer]

I have the One Way dovetail jaws what I did is clamped the woodworm screw in and measured the diameter then use that when making the dovetail tenon, while that may not be perfect it does the job.
As far as storing the jaws I don't worry about it, I have 2 Strong hold chucks one of them has the larger dovetail jaws installed and the other has the smaller jaws (not the dovetail). The

 

[Paul Paukstelis]

Why not just measure it? If you measure from a jaw corner to the opposite jaw corner, and then across the center of the jaws, the spot where that measurement is the same is the perfect circle. You can then set your dividers to that value.

 

[Holmes Anderson]

Ok, now I understand the dimension you want. It could be relatively simple to calculate perfect circle diameter from the listed closed circle diameter for the entire Oneway line using only one kerf measurement.

1. Measure the kerf from the Oneway machining process by setting a Oneway jaw set in a perfect circle and measuring the gap between adjacent jaws.
2. Create a spreadsheet that calculates the perfect circle diameter from the fully closed diameter by:
a. calculating the fully closed circumference from the fully closed diameter listed in the Oneway data sheet (2*pi*(d/2));
b. adding the kerfs (4*k) to the closed circle circumference to approximate (because the kerf measurement was linear) the perfect circle circumference;
c. calculating the perfect circle diameter from the perfect circle circumference.

If you are familiar with spreadsheets, then this is a 15-20 minute task. The assumption is that the kerf is consistent across the entire Oneway line. I measured about 1mm for #2 tower jaws with a steel ruler and not much care (about 3mm for the largest Vicmarc jaws). You might decide to use calipers.

 

[Don Wattenhofer]

Ok, now I understand the dimension you want. It could be relatively simple to calculate perfect circle diameter from the listed closed circle diameter for the entire Oneway line using only one kerf measurement.

1. Measure the kerf from the Oneway machining process by setting a Oneway jaw set in a perfect circle and measuring the gap between adjacent jaws.
2. Create a spreadsheet that calculates the perfect circle diameter from the fully closed diameter by:
a. calculating the fully closed circumference from the fully closed diameter listed in the Oneway data sheet (2*pi*(d/2));
b. adding the kerfs (4*k) to the closed circle circumference to approximate (because the kerf measurement was linear) the perfect circle circumference;
c. calculating the perfect circle diameter from the perfect circle circumference.

If you are familiar with spreadsheets, then this is a 15-20 minute task. The assumption is that the kerf is consistent across the entire Oneway line. I measured about 1mm for #2 tower jaws with a steel ruler and not much care (about 3mm for the largest Vicmarc jaws). You might decide to use calipers.

The method I used, which I explained in reply #5, will give the perfect circle and that can be proven simply by positioning a tool rest against the dovetail and rotating by hand or if you want to get really picky setup a dial indicator.

 

[Webb Willmott]

Would you expound on the carrier design you have in mind?

 

[Gord Cameron]

Ed, I think that the dimension you are looking for is on the Oneway webpage that Holmes linked to above. The dimensions on that table appear to be the "design diameter" of the jaws. If you look at the schematic on the right side of the page, it says that the "A" dimension is for compression chucking (that is, on a tenon), and the description of this dimension on the schematic is "Use this measurement when grabbing on to a tenon". I doubt that Oneway would describe the dimension that way if it were not the perfect circle dimension.

I am not at home so I can't check the dimensions in the table against my Oneway dovetail jaws to confirm this, but I have always used that table for my perfect circle dimensions.