Procedure For Boring Soft Jaws

I can't recall using soft jaws myself. I have seen others use them. Ussually they were used in conjunction with a medium size production run. I think they were bored a little smaller than the OD of the part so the outer edges gripped the part diameter so there would be six points of contact. I think the machinist used a steel ring. The ring was placed over the soft jaws. Then they were expanded to hold the ring tight leaving the inside clear to be bored out to size. I saw something the looked like a three sided star shape that the jaws could be tightened down on so the outer diameter of the jaws could be turned to size if the part needed be held by its inside diameter. I hope I have explained it clearly, I can see it in my mind but sometimes putting it in words is hard.
Its been a long time since I worked in that shop. One thing for sure that interrupted cut is hard on the tool bit.
 
I think what Joe wants to do is to use these soft jaws as all purpose jaws like the original ones that came with the chuck , as opposed to boring them to hold one particular part for a production run. I think he has a great solution to the very expensive problem of trying to buy new factory jaws for his chuck which has NO top jaws. I'm pretty sure this can be done, but am not sure how to go about it, so I will be watching for the "pros" to walk you through the process. PS. Joe, it might help if you show a pic with the soft jaws screwed on the chuck. Good luck, JR49

EDIT, Also, about the expensive "ring" to preload the jaws for turning, I have read many posts showing inexpensive shop made tools for this ,but once again, I will defer to the "pros"
 
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When I cut the chamfers they did act like soft jaws, not the hard top jaws. So I think a boring bar should work if you take small cuts. I was able to take .075 Deep cuts with my milling cutter with no significant issues.
 
They appear to be plain old soft jaws which will turn easily, if you are turning them for OD chucking use a suitable sized round in the master jaws far enough inside the chuck to leave clearance for the tool to pass through the soft jaws. If you are putting a pocket in the face of the jaws don't forget to remove the radius left by the boring tool in the corner of the pocket with an undercut, no special setting tool is needed for this. You want to have the chuck clamped in the same direction as when clamping the parts that you intend to turn.

Turning soft jaws for ID chucking will require a tool for this purpose whether it be a simple ring (of your own manufacture) or a tool made just for this purpose.

These are called pie jaws, they give nearly 360 Deg. work holding, I clamped a 1 1/2" diameter round in the master jaws then bolted the soft jaws on and turned an 8.06" diameter X .08 deep pocket to hold the VERY THIN parts required. easy a pie, no pun intended. They are 12" diameter on an 8" chuck made from aluminum from Monsterjaws.com I believe, well made and low priced, under $160.00 per set.
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Yes, What JR indicated is correct, when I purchased the lathe, there were no jaws other then the master jaws. So I do need something I can use as OD jaws for turning larger diameter parts. What if I milled the jaws oversize and then mounted the jaws and used the boring bar to true up the jaws to the center line of the chuck? Or would it be better to use a boring bar to turn the whole jaws?

I searched out on the web and the only posts I can find are those that are used to true up the inside of the jaws to correct bell mouth.

I hope I do not have to purchase a new chuck.

Thanks

Joe
 
Thanks Henry, JR, Wreck Wreck and Bill C for the tips. I saw Tom Lipton use pie jaws in one of his videos.

Joe
 
If you want an accurate chuck there are only to options. Either grind the jaws, if the rest of the chuck is fine, or by a new chuck. At some point it is better to buy a new chuck than stay to an old chuck however good it may have been when it was new. In case the chuck has been in an accident like a being hit and stopped from high rev, or the scroll wheel is worn, it doesn't help to grind the jaws even if it is done professionally.

The backside if cheap chucks is that even though they may work fine when new with almost zero runout, the material quality is often low and the chuck will wear much faster than a premium chuck. But for hobby usage it can be okay to use a new cheap chuck that is e.g. just 20% of the price for a premium chuck.

I have both expensive chucks and cheap China chucks. The one I use for most of what I am doing, and is happy with, against expectations, is a 150 dollar 6 jaws chuck. One of the reasons it works fine is that it is mounted on a back plate, so the runout could be adjusted.

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Joe,
It is perfectly feasible to bore your soft jaws the way you want them. You will learn how to manage interrupted cuts.
I have cut through the spokes of a cast iron pulley with no problems. Obviously you need a very ridgid set up.
The radius of the bore will depend on how you have preloaded the jaws.
Diameter of boring bar should be determined by length of bore.
I would preload the jaws using pins in the jaw bolt holes tightened against a ball bearing race to locate the jaws.
 
Thanks Micke for the insight and pix.
Thanks Tozguy for the procedure.

Joe
 
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