# Procedure For Boring Soft Jaws



## Joe Pitz (Jul 23, 2015)

Hello All,

My lathe came with a 6" chuck with no jaws.

Henry, (hvontres)  sold me a set of jaws and now I would like to mount and bore them.

I checked out on the web for a procedure for boring jaws and only saw a procedure for boring jaws on a CNC turning center.  Of course on a CNC turning center the turret can move horizontal and vertical. 

So I am wondering how to do this on a manual lathe.

Also all the examples indicate that you must pre-load the jaws using a boring chuck jaw ring,  a rather pricey tool for a one time job.

Included are some shots of the  jaws.

If someone could enlighten me on the best way to bore two steps on the jaws. Is there a substitution for using a chuck jaw ring?

Could this operation be done with a boring bar?  I am having trouble visualizing how to do the multiple steps?

Would you change the length of the boring bar to get the steps?

Also it appears that the position of the jaws in the chuck, (during boring) is critical to how much of a diameter that can be turned.  If the jaws are not positions correctly your are limiting your diameter?


Thanks

Joe


----------



## tertiaryjim (Jul 23, 2015)

Joe
Most jaws are hard enough to cause problems even for carbide and boring isnt all that accurate . The best way is to grind them.
There are a number of threads on site to give you all the information you need. 
Do a search with "chuck jaws".


----------



## Joe Pitz (Jul 23, 2015)

Thanks tertiaryjim,  I will check that out.

Joe


----------



## RJSakowski (Jul 23, 2015)

There was also a post a while back about making a boring ring .  It used the beveled surfaces of the chuck jaws to provide outward loading of the jaws while boring.   Fairly simple to make one
http://www.hobby-machinist.com/threads/chuck-grinding.36645/#post-312446

Bob


----------



## Joe Pitz (Jul 23, 2015)

Hi Bob,

I did some searching for chuck jaw grinding out on the forum and out on the web.  It appears that everyone is giving examples of correcting for bell mouth in the jaws, at most they are removing just a few thousands off of the chuck.  I want to create the steps on the jaws.  This would be just under .500 a step, that is a big difference in amount of material removal.  Also I doubt that a grinding wheel would last that long, you would have to re-dress the wheel and or replace the wheel.

Would this same process be the best way or only way to cut the steps in the chuck jaws.

Thanks for the info on the boring ring.

Joe


----------



## T Bredehoft (Jul 23, 2015)

Attack (gently) one of the jaws with a file. Does it 'skate' or dig in.  If the latter you can turn them if not, you can't.  In any case, if you do turn them, be aware that a lathe is not generally used as an 'interrupted cut' machine, the chuck will want to 'bounce' between the jaws, probably breaking your tool in short order. The slower you run it the less effect this will have, also, I'd hold my hand on the chuck to keep it from bouncing.  You might even rig up an old boot heel (or some such) as a brake on the chuck, just to put drag on it.
Of course, if you can't file it, you can't cut it. Perhaps the jaws could be cut on a mill.


----------



## JR49 (Jul 23, 2015)

Joe If what you have are in fact "soft jaws" then you should not need to grind them, as they should not be hardened like the factory jaws. As for the procedure for boring them, I will defer to others more experienced than I.  Good luck,  JR49


----------



## Joe Pitz (Jul 23, 2015)

Thanks Tom, I will check out the file approach and see what happens.

Thanks JR,  Yes Henry indicated, that when he purchased them, they were soft steel jaws, not hardened.

Joe


----------



## tertiaryjim (Jul 23, 2015)

Joe
Cutting steps in the jaws should be done before they are hardened. Removing that much material now could warp them.
Are the jaws hard?  You should also check with Henry as he might be able to provide all the information you need.
Edit: I see from posts put up before I completed this that I just rehashed what was already said.
Please ignore.


----------



## Joe Pitz (Jul 23, 2015)

Yes, tertiaryjim

Henry indicated that they were steel soft jaws.

Thanks

Joe


----------



## Bill C. (Jul 23, 2015)

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.


----------



## JR49 (Jul 23, 2015)

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"


----------



## hvontres (Jul 23, 2015)

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.


----------



## Wreck™Wreck (Jul 23, 2015)

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.


----------



## Joe Pitz (Jul 23, 2015)

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


----------



## Joe Pitz (Jul 23, 2015)

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

Joe


----------



## Micke S (Jul 24, 2015)

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.


----------



## Tozguy (Jul 24, 2015)

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. _


----------



## Tony Wells (Jul 24, 2015)

This may give you some ideas on the procedure:

http://www.hobby-machinist.com/threads/easy-soft-jaws.17043/#post-142284


----------



## Joe Pitz (Jul 24, 2015)

Thanks Micke for the insight and pix.
Thanks Tozguy for the procedure.

Joe


----------



## Joe Pitz (Jul 24, 2015)

Thanks Tony, these look great and so simple to make.  Are there any downsides to this configuration?

What diameter and thickness are the jaws, I guess it would not matter, but just to get an idea.

Also what is a spider?

Thanks

Joe


----------



## f350ca (Jul 24, 2015)

I often use soft jaws. I make mine out of aluminum thats been keyed to fit the profile of the masters but your steel ones will give the same results. As someone above said close the chuck on a suitable sized piece of stock grabbing it with the master jaws and machine the profile you want in the soft part with a boring bar. If you want steps to grab on the ID of a part you will need to expand the chuck on a piece of pipe over the outside of the jaws to remove the slack.
If milling the waste material away is going to be quicker than making the intermittent cut go for it.
My aluminum ones wear fairly quick if Im making a run of parts, your steel ones will be better but will of course wear faster than hardened ones. The beauty of the soft ones is it only will take a few minutes to reface them.
I use the soft jaws sacrificially to hold parts that I don't want to damage, say a gear. Machine a pocket in the face the size of the part you want to hold, remove the blocking piece from the hard jaws and the gear will then be held with virtually no runout.



Greg


----------



## Joe Pitz (Jul 24, 2015)

Thanks Greg for the info this helps alot

Joe


----------



## JR49 (Jul 24, 2015)

Joe, I just read the post that Tony Wells linked to, and came up with an idea.  For pre loading the master jaws toward the OD, you could use a large SS screw clamp,  like a hose clamp only big enough to fit around the chuck circumference. put the clamp on chuck covering the T-slots, then expand the jaws out until they push against the clamp. Now they are "loaded" and you can turn the outside steps.  Tony, the pictures you linked to are the best tutorial on boring soft jaws I've seen, so thanks for that.  Hope this helps, Joe.  JR49


----------



## Joe Pitz (Jul 24, 2015)

Thanks JR, sounds like a good idea.  Great solution when you want to turn the OD on the jaws.

Joe


----------



## Tozguy (Jul 24, 2015)

this is what I call a spider


Joe Pitz said:


> Thanks Tony, these look great and so simple to make.  Are there any downsides to this configuration?
> 
> What diameter and thickness are the jaws, I guess it would not matter, but just to get an idea.
> 
> ...


----------



## Joe Pitz (Jul 24, 2015)

Thanks Tozguy,

Now what is it used for,  sorry newbie question.

Joe


----------



## Tozguy (Jul 24, 2015)

Joe, keep the questions coming , I love it!

A spider is used to hold stuff with better concentricity than is possible with conventional lathe chucks. I use it for holding reloading dies or short gun barrels. I have a different spider for chambering long barrels thru the headstock.

The adjustment screws along with a dial test indicator allows me to get a level of concentricity that is only limited by my patience.

BTW this spider was made from the hub of a faceplate that I found at the scrap yard. Note the interrupted cut required to salvage the hub. This pic shows what is left of the face plate.


----------



## Joe Pitz (Jul 24, 2015)

Tozguy,  So if I am understanding, you mount the barrel in the center and used the set screws and a dial test indicator to get the concentricity?

That is way cool.

Thanks

Joe


----------



## Tozguy (Jul 24, 2015)

You got it Joe.
Thanks for the compliment.
Been looking out for a suitable piece of scrap to make one for a while. When I finally found something suitable it was a blast to make.
Making my own D1-4 studs is especially fun. Not counting the purchase of some high quality taps for the female threads, it cost around $15.


----------



## Tony Wells (Jul 24, 2015)

Joe, I haven't run into any problems using the cheater jaws like that. Commercial soft top jaws would be stronger of course, being properly keyed to the master jaw, plus they would repeat better when you needed to put them back on. But if you are making a set as more or less permanent top jaws that wouldn't matter. You can buy those ready to machine from a couple of places if you don't want to fit the keyways, etc on the master jaws.

I think that the cheater jaws work as well as they do is that for second ops, or close concentricity chucking, generally the part is a little delicate so you aren't really chucking hard anyway. Those I showed are aluminum, but just for ease, and I have a pile of 2 1/4" drops I can use for that. Steel would be just fine.


----------



## Wreck™Wreck (Jul 24, 2015)

Micke S said:


> 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.
> 
> This is untrue my friend, there are often times when the work is completely unsuited to using  hard top jaws, holding parts on previously finished surfaces for a second operation is one example. Holding parts that are very thin or have complicated geometries is another. Holding very short parts that do not easily lend themselves to a through spindle stop is probably the best use of soft jaws.
> 
> ...


----------



## Micke S (Jul 25, 2015)

I certainly agree a two piece 6 jaw chuck would be a lot more versatile.  Especially if it is with soft and hardened jaws. But the price may require being on a strict diet for a month


----------



## kinggt4 (Jul 28, 2015)

Mikes

Where did you get the San Du 6-jaw chuck??

George


----------



## Micke S (Jul 28, 2015)

Here http://www.alibaba.com/product-deta...0235541706.html?spm=a2700.7743248.61.2.2VXT2n

I was able to use Paypal even if this was not listed. WU is not my thing. It costed me 200 with shipping about a year ago.


----------



## kinggt4 (Jul 28, 2015)

Micke,

Thanks very much.  Where did you get the adjustable? backplate to fit?

George


----------



## Joe Pitz (Jul 28, 2015)

Thanks Tony for the info on the cheater jaws.


----------



## Micke S (Jul 29, 2015)

kinggt4 said:


> Micke,
> 
> Thanks very much.  Where did you get the adjustable? backplate to fit?
> 
> George



I drilled new holes between the old ones in the original backplate. The holes are 0,5 mm wider than the bolts so the chuck could be dialed in.


----------



## Tony Wells (Jul 29, 2015)

You're welcome, Joe. Although my main lathe has a 3 jaw that I can count on to be with a couple, sometimes I find that I need to hold OAL or concentricity closer than that on a finished part, or work with thin, washer-like pieces, or thin wall parts as in that example a spool shaped part. I could have made a split sleeve for that particular part and chucked it conventionally, but it works out for multiple uses and is not a dedicated tooling aid.


----------

