Best Parting Tool for a 303 rod

[jbrookes]

I am parting a ss303 3/8 rod with 1/8 hole down center and length of 2.5 inches beyond the parting plane. Currently I am using a .090 solid carbide brazed tool that I have ground a 20 degree angle on with a diamond wheel. It leaves a burr on the parted piece. This is probably due to the fact that the long piece wobbles and tears itself away prematurely from the chucked stub.

I have thought of a "concave restrainer" consisting of a 180 degree half cylinder that is positioned to be close to the piece when the parting tool is close to cut-off.

On to the tool itself. I have an Iscar grooving tool and another tool that takes GTN-L2. I have thought of grinding an angle on the iscar insert or the GTL.

I worked with a cnc expert a few years ago, and he achieved good parting by varying the spindle speed right before parting. As I recall, he upped the rpm's and slowed down down the feed. Got rid of the burr. But that was a stubby part, and I am working with a 2.5 inch part now.

Any ideas? Thanks in advance.
JB

[dak1]

As you get close to center & the connection becomes weaker, slow the RPM down to minimize whipping. Set work csys as close to chuck face as possible (as you know). The narrower the tool you can use, the less force will be introduced, also helping to minimize whipping.

[jbrookes]

As you get close to center & the connection becomes weaker, slow the RPM down to minimize whipping. Set work csys as close to chuck face as possible (as you know). The narrower the tool you can use, the less force will be introduced, also helping to minimize whipping.

-I have a Nikcole insert (Travers Tool) that is .040 with 7 degree angle, so I may try that.
JB

[dak1]

Give it a try. Hopefully the insert holds up.

[jbrookes]

yes, think it will.
also the de-wobbler is worth a try, I am convinced. In theory, it can be precisely adjusted to be say .050 away fro part when cutoff happens.

[dak1]

Is this a manual machine?

[jbrookes]

Is this a manual machine?

No, its a cms cnc gt27 gang lathe with Fagor 8055 controller. Why?
JB

[dak1]

I was just wondering if there would be manual intervention for each part or automatic operation. How do you plan to mount the "steady rest"?

[jbrookes]

as easily as posible. One way is to take a 1/2 inch section of steel DOM, about an inch long, and weld a steel bar to it. This steel bar then gets trapped underneath the cutoff tool in the removable QCTP holder. It will have to jog to the right to trap the bar-to-be-cut-off at a point towards its end. And most importantly, be adjusted so it is centered on the cutting tool.

The way I make that is to use welding. So I plan to jig a 1/2 inch round bar in a V-block on a flat table. The half-round piece of the DOM tube mentioned above is then clamped to the 1/2 rod. The adjustable QC tool holder is then fitted with an "L" bracket plus cutoff tool. The the tool holder is placed flat on the table with the cutting tip of the cutoff tool centered on the 1/2 bar in the v-block. It is also aligned parallel. Then the "L" attachment is welded to the DOM section.

Sounds complicated, but much easier than machining. The only catch is to get DOM tubing close to 1/2 ID.
JB

[ProProcess]

To prevent the burr, a nice sharp edge is your friend.
I would also increase the angle to more like 45°, this keeps the material on the barside more robust and the break-away happens more gently, leaving less burr on the work piece.
I've done this for years on "00" B&S's.
Good luck.