Cant see how this can work??

[ukracer]

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[Wallace]

The chuck jaws are tightened on the ring to keep them against the scroll and the grinding bit is passed through the jaws to reface them. Each pass the top slide can be moved to skim a little more off until the jaws are refaced.

 

[slim_boy_fat]

Presumably your drilling measurements for the holes for the locating pins would need to be dead accurate?

Or is the ring assembly a 'stand-alone' gadget?

 

[ukracer]

Presumably your drilling measurements for the holes for the locating pins would need to be dead accurate?

Or is the ring assembly a 'stand-alone' gadget?

Thats the point. THis is what they wrote.

"
The picture here shows a chain saw sharpener (25K RPM) mounted to a Aloris post. Simple but very effective.
The pins on the front of this chuck are 1/8 dowels, and the holes were drilled with a 1/8 masonary bit (with water cooling) and exact hole location is un-necessary, as the ring loads the jaws irrespective of location.
Mark the contact point of each jaw with a felt tip marker.
As you grind, you will see the contact point move outward as the ink is ground off. as soon as all ink is gone, spark out , and quit."

Does not make sense to me..

 

[GrahamGKD]

Presumably your drilling measurements for the holes for the locating pins would need to be dead accurate?

Or is the ring assembly a 'stand-alone' gadget?

I guess you could tension the jaws against the scroll by putting something in the chuck and then drill using the same head as is being used to grind the jaws above? The cross slide would need to be locked off. Are chuck jaws not hardened though - I presume these must be soft jaws, unless they come per-drilled?

 

[ukracer]

The chuck jaws are tightened on the ring to keep them against the scroll and the grinding bit is passed through the jaws to reface them. Each pass the top slide can be moved to skim a little more off until the jaws are refaced.

I can see that part mate but its the holes he has drilled into the chuck. He actually says they do not need to be accurate when I would have though they had to be spot on....

 

[bc30se]

wouldn't it be just better to make a ring and hold it on the outside of the jaws?... doesnt make too much sense to me in this configuration...

 

[ukracer]

I guess you could tension the jaws against the scroll by putting something in the chuck and then drill using the same head as is being used to grind the jaws above? The cross slide would need to be locked off. Are chuck jaws not hardened though - I presume these must be soft jaws, unless they come per-drilled?

http://www.chaski.org/homemachinist/viewtopic.php?p=173660#p173660 This might help to see what they are saying..

 

[GrahamGKD]

Thats the point. THis is what they wrote.

"
The picture here shows a chain saw sharpener (25K RPM) mounted to a Aloris post. Simple but very effective.
The pins on the front of this chuck are 1/8 dowels, and the holes were drilled with a 1/8 masonary bit (with water cooling) and exact hole location is un-necessary, as the ring loads the jaws irrespective of location.
Mark the contact point of each jaw with a felt tip marker.
As you grind, you will see the contact point move outward as the ink is ground off. as soon as all ink is gone, spark out , and quit."

Does not make sense to me..

Ah, yes, I see it now. As it says, the ring just loads the jaws - it doesn't matter where the pins are.

 

[ukracer]

wouldn't it be just better to make a ring and hold it on the outside of the jaws?... doesnt make too much sense to me in this configuration...

Thats what I was going to do BUT I think that assumes the outside it accurate. IT possibly is better then the internal side of the jaws to be fair . They are bellmouthed. I know I am not gonna get perfection but I would like better work holding.

My plan is was to get a steel ring lazer cut so it holds the jaws just a bit smaller than the diameter through the headstock.

 

[GrahamGKD]

wouldn't it be just better to make a ring and hold it on the outside of the jaws?... doesnt make too much sense to me in this configuration...

No, because that would load the jaws the wrong way against the scroll, if I understand it correctly.

 

[ukracer]

Ah, yes, I see it now. As it says, the ring just loads the jaws - it doesn't matter where the pins are.

Thats what I dont follow. If those pins are out surely it will be out when its been ground or bored.

 

[ukracer]

No, because that would load the jaws the wrong way against the scroll, if I understand it correctly.

Thats also why I like this idea. http://lathe.com/tips/chuck-jaw.htm How to get it made accurately I am not sure yet.

 

[GrahamGKD]

Thats what I dont follow. If those pins are out surely it will be out when its been ground or bored.

The ring isn't rigid enough to hold the jaws in a specific position. It is the scroll in the back of the chuck which is holding the position of the jaws. The purpose of the ring is just to tension the jaws against the scroll (take out the backlash).

 

[ukracer]

The ring isn't rigid enough to hold the jaws in a specific position. It is the scroll in the back of the chuck which is holding the position of the jaws. The purpose of the ring is just to tension the jaws against the scroll (take out the backlash).

I think I follow what you say but my age is against me sadly

 

[MattF]

I think I follow what you say but my age is against me sadly

The ring will distort slightly, plus it will move around if one jaw is pressing slightly more. When all three jaws are pressing against the ring, any free play is gone, and it's the scroll which is responsible for their ultimate position. Spot on they may not need to be, but the pins would need to be something like.

 

[Wallace]

I can see that part mate but its the holes he has drilled into the chuck. He actually says they do not need to be accurate when I would have though they had to be spot on....

If the ring has some flex/give in it i.e. not hardened then any inaccuracy of the pins would not matter greatly so long as the jaws are kept against the working side of the scroll. Holding the jaws externally would not take into account any wear in the scroll or jaws for tightening down on the outside diameter of the work. You wouldn't drilll the pin holes freehand with a cordless but they wouldn't need precision grinding either.

 

[normspanners]

The ring isn't rigid enough to hold the jaws in a specific position. It is the scroll in the back of the chuck which is holding the position of the jaws. The purpose of the ring is just to tension the jaws against the scroll (take out the backlash).

Thats how I see it, the inside of the scroll's machining of it's 'thread' denotes the jaws separate positions when locked onto something, anything, even a piece of steel tube would do, what you are doing is paralleling each jaw and equalizing the distance between the inside of the scroll to the object tightened in the chuck.

 

[CRB]

View attachment 58625
Thats also why I like this idea. http://lathe.com/tips/chuck-jaw.htm How to get it made accurately I am not sure yet.

You could do it on a drill press, but because it is only to give the jaws something to grip, you could be a millimeter out and the three points of contact would average out.

 

[mechman]

You could do it on a drill press, but because it is only to give the jaws something to grip, you could be a millimeter out and the three points of contact would average out.

aarrgghh me heed