Bull Nose Live Center

[Ray C]

Ray,
A couple questions.
Why didn't you turn the MT first and do your boring with the piece held in the H.S. MT?
Also, would it be "better" to grind your 30° point after completion? I wouldn't know how you'd hold the MT though unless you did it in the H.S.
These questions are mute though as yours turned out perfect but curious to your answer.

Excellent question!

If I cut the taper early on, I would not want to risk doing that many boring and facing operations on a piece only held in the spindle with a Morse adapter. The headstock has a native MT5 taper so, a MT5 to MT3 adapter would be needed. That arrangement works fine to hold a dead center but, it would not hold a workpiece -especially if any kind of side pressure is applied. I can almost guarantee that would have a very bad outcome.

Immediately after the part was heat treated, it was cut the entire length and the big and small outer diameters were made perfectly straight and concentric. If the taper were cut early on, I would limit the options for holding the piece and also reduce (by over 50%) my ability to indicate the part over it's whole length. You can never indicate a part in one place and assume the entire length spins true. Since the small diameter was under 1-1/16", a 5C collet chuck was the natural choice to hold it. I'll add to that and mention that my 5C collet chuck is as close to perfect as is humanly possible.

The take-away here is that you can only use the headstock taper to spin between centers whereby the tailstock pressure keeps the part held firmly. If the tailstock pressure is compromised, the two interfaces in the headstock (headstock itself and the adapter) will give way. That's almost a foregone conclusion.

Good questions...

Ray

 

[ddickey]

Okay thanks.
I guess I thought as long as you are not taking big DOC cuts it would be okay to turn in the MT HS. Thanks for clearing that up. I won't try that.

 

[Ray C]

Okay thanks.
I guess I thought as long as you are not taking big DOC cuts it would be okay to turn in the MT HS. Thanks for clearing that up. I won't try that.

Best not to try that. A part held solely in the headstock taper could go flying -for sure.

Ray

 

[turnitupper]

Could use a drawbar through the spindle.
John.
P.S. Very pretty work.

 

[ddickey]

Ray,
I'd like to make one of these but I can't see the dimensions.
Could you post them again maybe in a different format?

 

[Ray C]

Ray,
I'd like to make one of these but I can't see the dimensions.
Could you post them again maybe in a different format?

Certainly... Later this evening, I'll post something in a better format. Keep in mind, that economically, you're better-off purchasing one. I did this just to see if I could pull it off and went into this fully aware that it might not turn-out successfully.

Ray

 

[Ray C]

Here you go... These are not classic mechanical draftings but rather, 2D profile parametric diagrams used to create the CAD images. Everything is fully specified to laborious degree. The format is PDF. Just open the file but do not activate the 3D image rendering and you should be able to see all the dimensions and values.

Regards

Ray

 

[Downunder Bob]

Best way to heat bearings is put them in a container with suitable bearing oil and heat it slowly with a thermostat control, (borrow your wife's electric frypan, When she's not looking). Your deep freezer is also a handy way to chill the shaft.

 

[ddickey]

Best not to try that. A part held solely in the headstock taper could go flying -for sure.

Ray

What do you think about this little do-dad? Good idea, no?

 

[Ray C]

What do you think about this little do-dad? Good idea, no?

Sure that works... He is making a spindle-side dead center with a built-in drive leg. I've done similar things by taking a piece of shop-drops, tapping a hole in it then, putting it in the 3 jaw and cut a point on it. Once that is done, I can insert a bolt in the threaded hole to serve as the drive leg. It's a one-time use thing but, works fine when I don't feel like mounting the dedicated drive plate.

I've also been known to tack weld a bent shaft to the workpiece then, mount it in one of the older chucks. The bent leg gets driven by one of the chuck jaws.

There's a million ways to skin that cat...

Ray