Machining soft Jaws Lathe ?

[Tin Falcon]

When setting Up my little Machinex 5 lathe I discovered the hard jaw of the chuck was hitting the material before the soft Jaws. I wanted to make a new spare set anyway but did not like being forced into it.
I know the general procedures for soft jaws it to chuck up a spacer/washer in the back of the jaws and bore to diameter leaving a shoulder. I did that and it works fine for short pieces but I would like to put material through the head stock on this.
So how do I load the chuck/ jaws so the jaws do not move while through boring/truing.
My thought was to bolt a plate to the face of the jaws with the jaw mounting holes.
Had anyone done this one a taig/ Sherline sized lathe?
this is a 3" Tommy bar style 3 jaw scroll chuck.
the spindle threads are an odd size so this limits options some . I can and have made back plates for a lathe like this (One for a friend) but I have a factory chuck. they are rare and would like to use it.
So ideas options please.
While typing this I jut realized I may be able to chuck up an aluminum slug on the hard jaws need to take closer look.
but other ideas or confirmation could be helpfull to others as well as this old bird LOL



Tin

 

[kvom]

Assuming that the hard jaws are two piece, then you just need the soft jaws to be longer than the hard.

 

[Tin Falcon]

Yep did that but now I need them true though.
Tin

 

[steamer]

Load a pin in the hard jaws and then bore the soft jaws. That will preload the jaws and remove any slack, making them repeat when closed on the bored diameter...as long as your grabing on the OD. IF your grabing on the ID, then you need to load the master jaws with a ring of some sort.

Dave

 

[Tin Falcon]

well looking at it some more . the problem I was having was the hard jaws were hitting the spindle threads before the soft jaws closed . like i said made longer ones.
So no real way of loading the hard jaws. Unfortunately I think I am dealing with a poor design.
but I did find another option that could work
http://www.prattburnerd.com/products2010/Pg81 Machining Soft Blank Top Jaws.pdf
Machine a shoulder on the face of the soft jaws and then chuck a loading ring then true the tips of the jaws.
If this was a sherline ,Taig or even an craftman dunlap I would just buy a chuck from 800 watt on ebay. But ....
you just have to love these orphans. Tin

 

[mocaquita]

Hi,
I assume you want to bore an ID in the soft jaws. I've done this frequently by using a thin (1/8") 3 lobed cam disc than sits against the chuck face and is thin enough to be clamped by the master jaws while not touching the softjaws, allowing you to bore the jaws. The cams allow you to adjust the size. This item is commercially available, but you can make one or simply make a round one of the appropriate diameter to do one size. Takes care of the problem where the master jaws are extended out to far to use a piece of round stock inside the chuck. Look about half way down this page at a set. http://www.ajaxjaws.com/wizzc/wizzg.html

Dave

 

[Tin Falcon]

Dave interesting link ,although a bit pricey for my home shop budget. I do like learning about tools options etc. Some things there I have never seen before. between the answers and the web surfing I think I sorted it out.
I started looking for something to use as a ring on the face.
My first thought was a 1/2 inch washer 9/16 ID 1.390 OD . It would work . Then I spotted flanged bushing 1.125 od .814 ID and 1/6 thik flange this should work grate. so I load the middle with a plug. machine a shoulder on the face to fit the bushing / ring then true up the tips of the jaws . an extra step but se la vi.
Thanks for the help guys.
Tin

 

[Tin Falcon]

well success finally bored out the soft jaws under cnc power. Used a button cell like the ones from the digital calipers as a plug held in the bore then bored a step for the bushing I mentioned then bored though 3/8. no crashes.
and the compulsory photo

Tin