Quick ? about 5c collet on lathe

[pontiac428]

I treat collets as if they are true (I spent a little extra so I could). Drilling is not an exact process, though, and there are a bunch of techniques people use to improve the odds. Bore when you can, if it's a small deep hole you can use a single flute bit and peck your way through...

 

[GT-6 Racer]

I treat collets as if they are true (I spent a little extra so I could). Drilling is not an exact process, though, and there are a bunch of techniques people use to improve the odds. Bore when you can, if it's a small deep hole you can use a single flute bit and peck your way through...

I agree, I have good condition, high quality collets (Hardinge, Monarch, Royal) in 2J, 3J, and Sjogren chucks that are quite true and repeat very well. Same for direct 5C in the Hardinge lathe spindles. I also treat them as true. Far better than any of my jaw chucks, even a brand new Buck 3 jaw I snagged at auction. I find the biggest thing with true concentricity really can depend on the surface finish and roundness of the stock being gripped. On the same note, I haven’t had such great luck with new import 5C collets and concentricity.
I really prefer to work with collets when the work fits in them.

If I need things to be really true then it’s old school between centers.

 

[verbotenwhisky]

I agree, I have good condition, high quality collets (Hardinge, Monarch, Royal) in 2J, 3J, and Sjogren chucks that are quite true and repeat very well. Same for direct 5C in the Hardinge lathe spindles. I also treat them as true. Far better than any of my jaw chucks, even a brand new Buck 3 jaw I snagged at auction. I find the biggest thing with true concentricity really can depend on the surface finish and roundness of the stock being gripped. On the same note, I haven’t had such great luck with new import 5C collets and concentricity.
I really prefer to work with collets when the work fits in them.

If I need things to be really true then it’s old school between centers.

Between centers is difficult if you are drilling a longitudinal hole. I use a boring bar if possible as I believe the best way to get a truly concentric hole is single pointing it. Just me.

 

[GT-6 Racer]

Between centers is difficult if you are drilling a longitudinal hole. I use a boring bar if possible as I believe the best way to get a truly concentric hole is single pointing it. Just me.

Yes certainly can’t do centers when making a hole. If I need better than collet concentricity I go to the 4 jaw for big stuff and a set-tru 6-jaw for little parts. Single point boring certainly gives the roundest most cylindrical hole if you can avoid the chatter.

 

[Investigator]

Thank you all, I got it sorted.
The issue was I needed a .750" dia portion with threads on one end. I had a 1" bar to start. I cut over length, and turned the .750 section, then flipped the part and put in collet. Then I could bore a hole, not a through hole, but it needed to be center bore in relation to the .750 section on the other end.

I'm sure it wasn't "perfect", but it was right.

 

[GT-6 Racer]

Excellent!! That’s the goal, make the part needed.