Machining square stock on a CNC lathe

[premier_industr]

I have a customer that I am currently making a wheel spindle for, ( one seal fit, two bearing fits and a threaded end ) from 3 1/2" 1045 round stock.

They are now looking at changing the design and using the same finish dimensions but changing the raw material to 3 1/2" X 3 1/2" square stock.

Up until now we have been facing them to length and centering the round ones in a manual lathe and then machining them complete in our CNC lathe.

Now with the square ones I will most likely have to face and center them on a mill, and then try to turn them in the CNC lathe.

I guess my question is, is there any way to grab the squre ones with a three jaw chuck in the CNC lathe ?

I may have the customer talked into turning one inch of the chuck end round in order to drive it in the CNC 3 jaw.

But I'm looking for other ideas that would not add a machining process to the the part.

Also, is there any precautions that can be taken to insure that the carbide insert will hold up from the square to round turning process ?

Its kind of funny in a way, the only reason the customer is changing the material from round to square is to eliminate some of there welding process.

But in reality what they are eliminating in welding costs they are adding to maching costs.

I'm not complaining because I'm profiting from the machining, but it seems like it is just a wash.

TK

[DareBee]

I would use a 4- Jaw scroll chuck but you maybe have one of those fancy hydraulic chucks on your CNC lathe that can not come off.

[beege]

Can you get "pie jaws" for your chuck? If you can, perhaps you can mill in the square off-line.

[HuFlungDung]

I like the pie jaws idea, although I haven't got a good notion of how I'd locate those jaws on the mill accurately enough to mill the square pattern on center

Perhaps you could make a long 'collet' for your chuck: take a piece of round stock, machine a square hole in it (somehow) to fit over the work stock, slit the collet almost through across a diagonal drawn through the square. Align the collet in the chuck (with the slit facing inward to the chuck) so that one of the three jaws is perpendicular to the slit. This should give you a clamping action similar to a 2 jaw chuck with V jaws.

How well this will be centered is unknown, but it should be close, or within range of a few thin shims if the work stock is cold drawn or something.

[PinMan]

If you have time and money constraints, the easiest and fastest way to do it would be to mill to length and centerdrill both ends. Then you can run it between centers on your lathe (possibly using a dog).
Otherwise, use a 4 jaw or get a collet chuck and buy a square collet for it.

[beege]

Originally Posted by PinMan or get a collet chuck and buy a square collet for it.

3½" Square?

[PinMan]

Ok, I misread the dimension a bit.
Although, you can get a 3J or 35J flanged emergency collet and machine a square into it if that is the way that you wanted to go.

[Shotout]

The last shop I worked for had a set of jaws for a 3 jawed 10in Kitagawa chuck that held square stock. The jaws had a pivoting end with a 90deg cut out that was off center to accommodate different sized square stock. I don't remember the size range it would accommodate but it I had a few jobs I ran that where 1.5in stock and 3in stock. The jaws where probably made by Kitagawa but I can't swear to it. For stock that was too large to fit in the spindle tube I did have to face and center drill the stock at the manual lathe.

[jstiltner]

I would ask the customer how centered the part needs to be. Specifically, is this a precision fit between whatever the square is being welded to and the round sections, If this is a wheel spindle then this dimension is probably pretty flexible. If you have a 4 jaw scroll chuck it should center it well enough. If you have a normal 4 jaw, work with it until one piece is pretty well centered, then loosen only 2 jaws and flip it around and drill the other end. This should get you pretty close to center. and unless they have a section that is 3.25" round, it shouldn't matter much if it is not perfectly centered on the square.

[premier_industr]

Being right on center is pretty important.

The part is 15" long and at about 8" in from the end the diameter for the seal fit finishes at 3.500 - 3.485.

Sometimes the spindles made from 3 1/2" round stock don't completly clean up at that point. ( about 1 out of 100 )

I did mention that to the customer, and his reply was don't look at me, thats what our " engineers " came up with.

Does anybody make steel soft jaws, that grab square stock, ready made, for a hydraulic three jaw chuck ?

[Delw]

theres now real way to use a 3 jaw chuck for square stock with out milling the jaws.

if you mill the jaws you need to make a threaded section with some flats and a ring on it to simulate the hydraulic pressure ie screw the parts you made into the back of the chuck to tighten the chuck on a spider that gives about the same force that you will be using.

if your chuck clamps on parts uneven over .05 out, you will bust your chuck or defnantly throw it out of sync over time, then it would be worthless on precise jobs.

there is always a way however.
make a fixture to locate in your chuck that accepts the square.
leave extra stock on the sqr. and cut a round location place on one end with a manual machine.
take a 5" chunk of alum the thickness of your jaws, cut the O.D. and bore a hole in it.
put it on the mill and cut a square into, cutting the corners out with a over sized drill bit or endmill to relieve to allow for the sqr corners then mill the sqr.. cut them in 3 equal piece's pin them to your jaws or weld them. this way you will always have jaws for this job.

cut a 5" dia section xx amount deep in your jaws in the lathe. take the jaws off and place them around the 5 inch ring you made pin them to your jaws or weld them. Then cut the ring in 3 equal sections with a end mill or band saw this way you will always have jaws for this job.

of you can get fancy and get some big stock turn the od and cut a small id hole for indication in it. on one side cut the serations in for the jaws then flip over and cut your square in then ith the bolt holes and c-bores then slice the jaws in 3 equal spots and end mill allowing room for closing.

we use to do lots of custom jaw cutting for some pretty wild and off center parts and castings.


with out seeing a print there is no way to tell you what to do.