Correct sie for spigot when using chuck

[wabbitpoo]

Am I right in thinking that for any set of chuck jaws there is an "ideal" spigot size to use, so the jaws operate at optimum hold with minimal or no crushing?

My Record chuck had no such detail in the instructions, so how do I know what is the best size to use? Just bigger than the diameter of the jaws when closed fully?

 

[PowerTool]

Yes there is,
And yes,probably - or possibly a little nearer to the middle of the range of travel of the jaws;there will be an optimum point where the jaws form a perfect circle,giving the largest contact area.

Andrew

 

[CHJ]

This helpWP, sounds like the relevant bit is "If all else fails you will need to set your jaws in a position that gives a true circle and check the internal and external dimensions"

Andrew is quicker at this typing lark :lol:

 

[PowerTool]

Not by much,Chas,and I never supplied pictures.. :wink:

Andrew

 

[beejay]

If you imagine that the four jaws were cut from a single piece, allow for the kerf of the blade that made the cut and that will give you the optimum setting/perfect circle.
Probably around a couple of mm.
regards, beejay

 

[wabbitpoo]

Surely if all the jaws move at the same speed as you open or close the chuck, then they will always form a a circle, won't they?

 

[Mark Hancock]

Surely if all the jaws move at the same speed as you open or close the chuck, then they will always form a a circle, won't they?

No. Think about it. The each jaw is a fixed arc /part of a circle so there is a point as they move in and out at which they create a circle.

 

[johnny.t.]

no, think of them completely closed and they would form a shape like a 4 petaled flower, as you open them they at some point will form a perfect circle.

JT
edit:
ha, beaten to it by Mr Hancock

 

[Jenx]

The jaws are quadrants Wabbit ... the circumference is a perfect circle at one point of the expansion of those quadrants only...

As you expand or contract them, the curve of the outside of those quadrants stops being 'circular' at all but the one point at which they actually ARE circular..

The wider you go..when expanding the chuck, the smaller the contact patch on the outside edge of each quadrant that will interface between a bowl's dovetail recess for example, will be. ( in expansion ).

Its always a 'trade off' between what's 'ideal' and what suits the piece you're actually making