Brainstorming

[pepi]

As a boot, this will go against, best practices, history and formulas. I am starting to question the tool speed of a mill and turning speed of a chuck, as it relates to quality of the finish.

Watching CNC equipment run and the finishes produced, what is common, they all use high rpms. That in mind, I have begun to up the tool and chuck speeds of my runs lately. Not extreme but starting at twice what is normally thought to be proper.

Knowing this adds heat and stress, I reduce the feed speed, and keep the cuts light. I am seeking a better finish as an end result.

So what are some the thoughts form the seasoned machinist that are here?  

Pep

[Highpower]

(07-14-2019, 08:03 AM)pepi Wrote: So what are some the thoughts form the seasoned machinist that are here?  

Pep

Well that eliminates me right from the get-go....

[awemawson]

Don't forget that the CNC machine will have oodles of coolant not only cooling cutters and workpiece, but also clearing away chips to prevent 'recutting'

[TomG]

(07-14-2019, 12:20 PM)awemawson Wrote: Don't forget that the CNC machine will have oodles of coolant not only cooling cutters and workpiece, but also clearing away chips to prevent 'recutting'

Exactly. Without coolant, even light cuts at twice the recommended speed will quickly dull tooling.

The best surface finish is generally attained by using light, climb cuts at the proper sfpm. Coolant, even if just misted on with a spray bottle will help as well.

Tom

[Dr Stan]

(07-14-2019, 09:07 PM)TomG Wrote:

(07-14-2019, 12:20 PM)awemawson Wrote: Don't forget that the CNC machine will have oodles of coolant not only cooling cutters and workpiece, but also clearing away chips to prevent 'recutting'

Exactly. Without coolant, even light cuts at twice the recommended speed will quickly dull tooling.

The best surface finish is generally attained by using light, climb cuts at the proper sfpm. Coolant, even if just misted on with a spray bottle will help as well.

Tom

Exactly.  Tool life will go in the toilet.

[pepi]

(07-14-2019, 09:07 PM)TomG Wrote:

(07-14-2019, 12:20 PM)awemawson Wrote: Don't forget that the CNC machine will have oodles of coolant not only cooling cutters and workpiece, but also clearing away chips to prevent 'recutting'

Exactly. Without coolant, even light cuts at twice the recommended speed will quickly dull tooling.

The best surface finish is generally attained by using light, climb cuts at the proper sfpm. Coolant, even if just misted on with a spray bottle will help as well.

Tom

Would it be safe to say Carbide Tipped or inserts provide some resistance there? And  the inserts are the better option of the 2 types?

Yes clear the chips, keeping the machined area, brushed and hosed down, WD power squirter

CNC machines are like Top Fuel, and my Pro stock machines will never produce the quality for many reasons . But can be tweaked to preform better if the right adjustments are made, and cutting hardware used.

I'm not kidding myself regarding the finish, just want to bring the quality up a few levels. In others words not expecting a mirror finish, but want to smooth out the tool marks more.

My thinking anyway and could be all wet also.

Pep

[TomG]

You'll get the best surface finish on light machinery, like most of us have at home, with a properly ground high speed tool bit. Carbide is capable of better finishes, but only when used on heavy machinery with more power and much better rigidity.

Tom

[Highpower]

Personally I've found the quality of the HSS tool blank makes a big difference in the quality of finish I get.

Cheap Chinese high speed steel tool blanks.

Some old Mo-Max tool blanks my FIL gave me...
Night and day difference.

[pepi]

I need to educate myself regarding tool bit grinding and the profiles. Finding the HHS tool blanks 1/2 x 8 extremely reasonable. Burning up a few will not be all that costly. Plus 8in blanks allow a few regrinds.  

Notice they are sold with a 15* rake. What is the purpose of that, understand it chip wise. But why would they put the relief in the blank, seems the user can knock that out.  Could it be a user quick start tool grind prep?

Looking forward to getting into the HSS tooling. Next  acquire the HF chain saw sharpener and adapt a green wheel for grinding ..... Dam will end up with 4 bench grinders when this is over, 2 stone & wire wheel,  tungsten and green wheel lathe tool grinder.

I have some bonded carbide HF tool bits, that kindly Jack sent to me. Saw where grinding the tool a tad back clearing tool material so as the tip hangs out a bit more, helps. So tried it and it does not to shabby.

Last but not least I was turning using what I have. My lathe has variable speed control. While turning I started to adjust the speed on the fly, added more control of the finish. Kind of like a ruff cut, dialing in the speed and run with it.

No I will never be grinding end mills, not interested, worth the $$$ to farm those out.

Cheers,

Pep

[Dr Stan]

When I learned how to grind HSS tool bits (MR A School) I was first required to produce one with acceptable angles from 3/8" sq 1018 steel.  I did the same with my students when I taught machining at a vo-tech.

You can obtain drawings with the recommended relief angles in South Bend's "How to Run a Lathe" booklet or in the US Navy's Machinery Repairman 3 & 2.  The latter is available as an on-line PDF.  IMHO both books are must haves for every machinist.