Turning finish

Agree with everything above- I rarely hone my tools anymore, often the honing will dull the tool if you aren't careful.
Make sure you have plenty of positive rake on the tool. Are you sure of the material? Just sayin'
-M
 
Thanks to all. Sorry for late reply, again.

Comment re: back rake. That was the main problem. Didn't have any, only side rake. Increased it significantly and much better results. It seems that steel needs some shear action? Still get a bit of build-up, but doesn't seem to affect the results.

Tool as modified with large back rake (about 20 degrees) below. Top view also. Tool is presented 90 degrees to work.

Also was getting tool angles a bit less than expected because my grinder tool rest is below the wheel center. So a 10 degree rest angle results in only a 7 degree tool angle, for example.

Comment re: RPM. I'll try a lower speed, though LMS table for 12L14 shows 200 - 260 FPM for HSS. Are these not correct?

On my lathe, I can't adjust feed rate independent of spindle speed as they are geared together. Is this not the norm?



IMG_4008.jpgIMG_4009.jpg
 
Good job including back rake.

Your nose radius is way too large. As it is now, that tool will deflect and you will have a lot of trouble bringing a work piece in on size. I highly recommend you re-grind the tool and put a nose radius of about 1/64 - 1/32" on it. You will find it will cut far more accurately and will still finish quite well. Look at a 1/32" diameter drill bit. That radius is what you want on your turning tool.
 
kmanuele said:
On my lathe, I can't adjust feed rate independent of spindle speed as they are geared together. Is this not the norm?
Click to expand...

Definitely NOT the norm:: how would you cut both ¼-20 and ¼-28 threads if the pitch was not independent of the RPM ?
 
kmanuele said:
On my lathe, I can't adjust feed rate independent of spindle speed as they are geared together. Is this not the norm?
Click to expand...
You can, you need to change the gears.
It is called a change gear set.
 
Mitch Alsup said:
Definitely NOT the norm:: how would you cut both ¼-20 and ¼-28 threads if the pitch was not independent of the RPM ?
Click to expand...

Maybe I was confusing 'feed rate' and tool speed. Newbie terminology confusion.

Feed rate, defined as inches per revolution (and not inches per second), is always constant for whatever thread pitch or power feed is selected -- regardless of RPM. Right, so far?

So the pitch, or feed rate, is independent of RPM, but not the tool speed.

Increase RPM, and the tool speed increases to maintain the pitch.

What I was trying (poorly) to say is that I can't change tool speed independent of spindle RPM.

K
 
kmanuele said:
What I was trying (poorly) to say is that I can't change tool speed independent of spindle RPM.
Click to expand...

You mean you don’t have additional gears with which to change the threading pitch or power-feed ratio?
 
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