# Easy Soft-Jaws



## Tony Wells (Aug 7, 2013)

I've often touted soft jaws for the lathe as a simple way to get around a chuck that perhaps isn't quite up to holding a part for secondary operations, or smooth round bar accurately. I had a need for some the other day and remembered to take a few pictures of an easy way to do a set. I'll try to get them in order.

The part and some drops from an old job:






Drilled thru and counterbored to fit the socket cap screws that normally hold the top jaws on.



Roughly the idea while laying on the surface plate.



Setting up to bore them to size and true them up. Note the 1/2" drive socket in the master jaws. This is to give the chuck something to tighten against for boring the soft jaws. You have to use something of the diameter that will allow you to bore the jaws to size and get as much contact area for the part to be machined as you want. In this case, I didn't want/need much area. You could work it so they would be like pie-jaws, but you would have to do something different that round stock as I show here. Like I said.. easy Soft-Jaws. 




Boring in progress.



Bored and ready



With part to be machined






Finished part in chuck




All this took about half an hour, including machining the part. TIR was near zero when finished. And of course, there's no way to get them back on the chuck exactly in the same position, but they can be rotated to a new position and bored there, or lightly chucking a part, snugged into place and skimmed. Or turned 90 or 180° and started from scratch. You can leave a shoulder instead of boring through as I did here if you need repeatable length chucking. I had to grab the inside of a spool shaped part, to I had to make sure they were short enough, and bored through. Uses only limited by imagination. I always get many uses out of the ones I make.


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## ScrapMetal (Aug 7, 2013)

Great tip!  I'm a bit surprised that the aluminum "cylinders" don't turn a bit when being hit by the boring bar.  Are they "really cranked down", do you use some other method to keep them from rotating, or is it just not an issue?

Thanks much,

-Ron


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## Tony Wells (Aug 7, 2013)

They are just faced flat on the back, but I'll admit that the soc cap screws, which are 12mm (I think), are pretty tight. I use a short arm hex key and a dead-blow mallet to knock them fairly tight. Being aluminum, even the smooth, ground surface of the "key" section of the master jaw bites in a bit. Never had one try to spin while boring them. But then, I don't get rough with them while boring. I don't want to mill a keyway to lock them onto the master jaws, since that would limit the use to only 2 positions, or 4 if I milled a crossing slot also. So, it's not an issue.


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## itsme_Bernie (Aug 7, 2013)

Thanks so much Tony!  This is fantastic


Bernie


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## Bill C. (Aug 7, 2013)

Tony Wells said:


> I've often touted soft jaws for the lathe as a simple way to get around a chuck that perhaps isn't quite up to holding a part for secondary operations, or smooth round bar accurately. I had a need for some the other day and remembered to take a few pictures of an easy way to do a set. I'll try to get them in order.
> 
> The part and some drops from an old job:
> 
> ...



Great idea. Thanks


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## eightball (Aug 7, 2013)

Slick


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## Tony Wells (Aug 7, 2013)

Glad you guys enjoyed it. These are, of course, aluminum. You can do these out of most any material you need. I like aluminum because it seems to grip well even with a small contact patch, and naturally, is easy to machine itself. And in this case, it was free. These were just some nubs left from machining some longer parts. I needed something to chuck on and machine complete and part off, so this was left over. 

I don't recall right off top of my head, but there is a company who makes a jaw system that allows for quick change jaw inserts that are designed to start basically as cylindrical blanks and you have to machine them as needed. I have a sample master top jaw for the system around here someplace. I'll dig it up and give the make at least, and show a picture. It's something that can be shop made, and it is actually pretty repeatable, so you can have jaws made for certain jobs/parts and just insert them into the top jaw and lock them in place with a set screw. It's a pretty slick system, although pretty pricey if I recall. I made a bunch of aluminum inserts for a set at a place I worked while I was getting my own shop rolling. They could have bought them, either steel (1018 or 1020), but wanted me to make some from aluminum. I still have the master top jaw that I used to get all the needed dimensions. I guess I am so used to using soft jaws for most everything like this that I don't need a collet machine too much. Not that I do that much small work anyway, but this saves me lots of headaches. 

I'll have to get used to collets on my project WatchLathe though.


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## greenhornet-1 (Aug 11, 2013)

Thanks!! Another tool i need to make.


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## dogbed (Aug 12, 2013)

I love it. So simple.


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## mtnlvr (Aug 12, 2013)

Thanks, great idea.


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## lrsglory (Aug 28, 2013)

ThOse soft jaws are just plain slick. Used to hate having to make a set in the shops. Co. wouldn't buy them. Possibly a few improvement to extend life and eliminate the possibility of one turning with heavy cuts. Increase diameter of soft jaw and mill a slot or multiple slots on the back to match the key on the hard jaw. you could end up with 2-4-6-8 positions to bore as the face got used up. Bore with the use of a spider locked in the hard jaw. Gotta repeat with a light skin cut when you put them back on to make a like or similar part. Whatcha think. 

Larry Smith  ( lrsglory )


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## Tony Wells (Aug 28, 2013)

Larry, I use whatever length is needed to hold the part. In this sample, notice I had a spool shape to hold, so they needed to be narrow like that. I have others that are longer. There really is no force in torque on the socket cap screws to unscrew them, so really no tendency to turn beyond when you are actually machining the jaws themselves. As they are wrapped around the work very close to the diameter being held, what little tendency to rotate the jaw is counteracted by the leverage arm between the centerline of the jaw along a radian acting against the radian from the spindle centerline to the edge of the contact patch. I find I use this type of jaw fairly often making thin parts. Think washer. Bore, turn, part off.....make as many as needed, then put the jaws on and face to accurate length and be parallel with the first face. They hold the part kind of like an emergency collet would. I get parallelism and TIR errors of a few tenths, typically. And wrapping around the part as much as needed, even thin plastic can be treated this way. I make some thrust bearings out of PEEK, 0.250 +/- 0.001 with this set up. Never lost one yet. I kike the safety of a round jaw too. Doesn't hurt nearly to bad to dust your knuckles as a regular jaw does. As long as you break the edges good on them when you make the rounds to begin with.

But for repeatability, you would need slots for the radial key on the master jaw, and either fit the socket cap screw very closely, or another key, male, offset outboard of the socket cap screw, as that is where the master jaw has it's keyway. Then it gets less convenient. Thus my claim to _easy_ soft jaws. They really work fine. And if you want to put them back close to where they were, you just snug them up against a piece of material that is the same size they were bored to, and they will clock themselves into position. Then tighten the socket caps and skim them true again. I would imagine match marking them to the master jaws would minimize the skim cut on most chucks. 

Thanks for bringing this thread back up. I had forgotten to hunt down that factory made replaceable jaw I promised. I'll do that today.


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## lrsglory (Aug 28, 2013)

See attached simple soft jaw lathe boring spiders made from hex nuts. Easy to set with deal calipers, measuring over a flat and a set screw end.


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## Tony Wells (Aug 28, 2013)

I've got some of those spiders someplace....hidden very well I expect. They do work well, and are adjustable so you don't waste anything boring out jaws. One place I worked where we used a lot of soft jaws we bought several sets of those think discs made for that, and in a few months time, most of the guys using power chucks had squashed them pretty good. They seemed to forget to turn the pressure down on the chuck when they bored the jaws. We tried this type of spider, and found that you can mash them down pretty easily with a hydraulic chuck....lol. But for a manual chuck, the work fine. I usually just dig around in the saw drops and find something close enough though. I'll never find my spiders. I guess I should make some more. It's a good idea.


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