QCTP progress and problems

[jumps4]

good job mike
that looks a lot better
steve

 

[wawoodman]

Thanks, Steve.

Now, I can get down to the nitty-gritty. I'm still seeing what looks like very fine "threads" on the piece. Is this a matter of feeds? I'm running at abut the middle of the range (I'm out of the shop, so I can't be specific.) But, what would be a good number that I should be using for the rough, and finish, cuts?

Or, do I need more of a radius on the cutter? Or, is this what it is, and I should finish with files and emery?

 

[jumps4]

it could be. the slower the feed the better the finish if the problem looks like a thread
also did you stone your edges or just grind? polishing the cutting edge with a fine stone may help
the pic looks like you put a radius on the point thats good
i'd try it slower first
steve

 

[jumps4]

it has a lot to do with the material
have you ever seen the cutters in a brake lathe for turning rotors I was a mechanic all my life and i really never paid close attention.
they are set at a negative rake, they look like they are just rubbing the side at about a 10 degree down angle
that has to be because it is cutting cast rotors because it works very well
so what works for one material may be the worst for another
I'm just learning myself
steve

 

[AR1911]

Mike,

You might want to try a vertical shear bit to get a little better finish. I find they work really well for really fine finish cuts. It makes really small steel threads - almost like steel wool. I can post a picture if you're not familiar with it.
Steve

After reading all the docs and links, I realized I'm doing pretty much the same thing with a cheap insert toolhold, the kind that uses triangular inserts with relief lip.
For finish skim cuts I rotate the toolpost CCW so that the point of the cutter is to the left, and the toolholder is at about a 35-degree angle from the work. This holds the cutting edge at about a 5-degree angle, again with the point to the left. I advance the crossslide to DOC and autofeed it left to right. It shaves off thin ribbons very nicely

 

[Tom Griffin]

Just a little reminder to those still learning the basics: The vertical shear technique is different and interesting, but also very specialized. It can only be used on simple diameters already rough turned to size. It won't work on a part with shoulders and it won't work if there is a lot of stock to remove. A decent finish can be obtained on pretty much any material by just following basic tool grinding guidelines, once they are learned and applied. It just requires practice.

Tom

 

[wawoodman]

also did you stone your edges or just grind?
the pic looks like you put a radius on the point thats good
steve

I stoned it with a diamond hone, but I could have done it better, I think. I radiused it by using the diamond hone, and (sort of) sweeping around the tip. Maybe it needs more?