10 Wheeler Rob wrote:Yes I do agree in the real world 3 jaws are very nessary to make $$$, my point was that for us hobiest the 4 jaw has a lot usefullness, in getting better percission.
True!
I've taken note that some folks really struggle with using a 4 jaw, but it's not hard at all. One of the things that makes it easier is to pay attention to jaw location. The concentric rings on 4 jaw chucks are there to aid in doing so-----and the jaw as it relates to the OD or ID of the chuck is yet another way, although not quite as precise.
Are theres souces out there to get soft jaws for alot of the old chucks us hobist have
It's somewhat unusual for one to purchase soft jaws, although I'm sure that those that are in production with CNC machines are likely to purchase them instead of making them. Problem is, as you've noticed, the home shop chucks tend to come with two sets of jaws, neither of which will accommodate conventional soft jaws. In order to mount the typical soft jaw, the chuck should be equipped with master jaws, or two piece jaws. The soft jaw mounts in place of the top jaw, and is easily made from flat bar steel or aluminum.
And soft jaws typically machined the dame way with a disc clampted in the back and then the high spot ground off after?
Depends on the job at hand. Soft jaws aren't always bored through. It's desirable to bore a step, or counter bore, which matches the part in question. That way, when a part is inserted, it is automatically registered for square, and makes working lengths dead easy. One can work from an indicator or DRO, having already established a reference point. Keep in mind that this is a production method, but is very useful for the home shop type, particularly if the project at hand requires more than one piece. I offer, for example, machining a set of wheels for a locomotive.
Assuming one wanted to bore a set of straight jaws, as long as the soft jaw is somewhat below the surface of the master jaw, the spider, or ring you speak of, is placed behind the soft jaw, on the master jaw, so the soft jaw can be through bored. I use jaws like that in my chuck. Once bored, even though they don't necessarily fit the material in question, they are far superior to the factory jaws in precision, and will drive the material under all but the most severe of conditions. I rarely use the factory jaws.
Here's a link to a thread on a different forum, where a person has made soft jaws for a conventional chuck.
http://www.homeshopmachinist.net/bbs/sh ... =soft+jaws
I highly recommend you read the entire thread and glean some ideas on how you can pursue the use of soft jaws without buying a new chuck. I also highly recommend that if you try the idea, that you make jaws that are a snug fit over your hard jaws, and can be bolted securely so they can't come off under speed. That's easily accomplished by milling a slot in the soft jaws, which then goes over the hard jaw much like a stocking. The bolt would not have to go through the hard jaw, just above it.
I only have hard jaws in all fothe chucks I have, one trick i use a lot is to make a alunimum ring of 6060-T6, saw a spit in it and clamp the part through the ring. This protects the suface under the hard jaws fom damage and usually grips fine for lighter cuts, drilling and boaring.
Only problem is that it does little to improve running accuracy, and nothing towards registering the part. Soft jaws are a huge improvement over that method, and can be used for roughing operations as well as finishing operations.
It is generally desirable to re-machine the soft jaws after the roughing operation. That way the jaws match, perfectly, the finish diameter(s), and have a clean surface that won't mar the work piece. Note that it's important to work to a specific size, so the soft jaws will perform as desired. Holding the diameter to ± .001" is usually close enough, and increases one's skill level considerably by doing so.
I have also used the slpit ring to grip hex stock in round collets and the like with very good sucess. The aluminum really grips the hex stock good and dose not bur up the edges of the hex, even when the hex is brass.
That idea is common in the job shop, and not only for hex stock. It's a good trick for round stock, too, when the proper collet may not be at your disposal, and time doesn't allow for the purchase of one. It's not usually necessary to split the bushing (ring), assuming it is thin walled. The number of jobs I've run that way would be hard to count. Again, precision plays a role. All the parts must be of uniform size for the unsplit bushing, or ring, to work. If they vary widely, splitting is often the only option. My work habits were such that I could use one that wasn't split.
If you're interested, I posted a few years ago on soft jaws. There's a lot of good information in the thread, so I'm providing the link for your perusal. Hope it sheds some light on the use of soft jaws for you.
http://www.chaski.org/homemachinist/vie ... php?t=4266
Harold