Barpuller for Hex stock?

[Heinz Putz]

Has anyone worked with a barpuller for hexstock?
.75" across the flats.
It seems easy, but!!
I worked out the problem of making sure to chuck on the flats when the chuck opens:
Chuck on the flats when you load the bar, then open the chuck so little during the auto pullout that you stay on the flat.
The barpuller can not come in from the side, for obvious reasons, it has to rapid to X0 and feed in from the front without grabbing across the points.
Any suggestions?
I really appreciate any help.
Heinz.
www.doccnc.com

[angelw]

Originally Posted by Heinz Putz

Has anyone worked with a barpuller for hexstock?
.75" across the flats.
It seems easy, but!!
I worked out the problem of making sure to chuck on the flats when the chuck opens:
Chuck on the flats when you load the bar, then open the chuck so little during the auto pullout that you stay on the flat.
The barpuller can not come in from the side, for obvious reasons, it has to rapid to X0 and feed in from the front without grabbing across the points.
Any suggestions?
I really appreciate any help.
Heinz.
www.doccnc.com

Hi Heinz,
Clearly the machine doesn't have indexing on the main spindle, or you wouldn't be asking the question.

One method I show clients when using hex, is highly dependent on the what machining operations occur on the outside of the part. If there's an OD turning operation that results in a diameter small enough, compared to the AF size, to tolerate an annular groove being machined in the next part not yet made in the bar stock, then a finger type bar puller can be used. If this is possible, proceed as follows:

1. Make a bar pulling tool similar to that shown in the attached picture. The picture shows the front view of the tool as seen from the chuck. The shank part of the tool can be salvaged from an old turning tool, or made from square stock with a cross section the same as that of the turning tools used with the lathe.

2. The finger part of the tool need only be thick enough to resist bending when pulling the bar stock to length. In most cases 4mm is ample. Obviously the groove in the finger needs to be slight clearance on the diameter of the annular groove used for engagement of the fingers.
3. After the completed part has been parted off, machine an annular groove at the appropriate Z position and diameter in the bar stock with the parting tool. The groove needs to be slightly wider than the thickness of the blade of the bar puller.
4. To pull the bar to length:
i. Stop Spindle
ii. Call Bar Bull tool and move to be aligned in Z with the annular groove machined in the bar stock, and clear in X
iii. Using Feed/Min mode, feed the Bar Pull Tool in X so as to engage with the annular groove.
iv. Open chuck and pull bar to length.
v. Close chuck and disengage bar pull tool from workpiece by feeding in X+ direction
vi. Carry on to repeat the part machining and bar pulling process.


Hope this helps Heinz.

Regards,

Bill