Ignoramus19981 wrote:

On 2011-02-22, Pete C. wrote:

Ignoramus562 wrote:

On 2011-02-21, Pete C. wrote:

Wes wrote:

Ignoramus17758 wrote:

In steel, however, this little 1/8" endmill works for a while, then
breaks after 1/2 hour.

Why not use carbide? If you push it too hard it will break quickly. If HSS is breaking
after 30 minutes on a cnc, I suspect you got the life time out of it.

Look at his cut parameters, as Dan noted, his chip load is 0.000125 per
tooth. His feed is too low and the end mill is rubbing and dulling.

I think that you have an extra zero in your calculation.

No, the calculation Dan posted is correct:

"So your chip load (per rev) is 1"/2000rpm = .0005"per rev.
/4(flutes)=0.000125."

1 IPM / 2000 RPM = 0.0005" of feed per revolution of the end mill,
divided by the 4 flutes = 0.000125" chip load per tooth, which is too
low by a factor of probably 10X.

OK, great, sorry.


A little update: I am now using a 12L14 bar that is exactly the right
diameter. I drilled a hole in the middle with a drill bit and am
machining the teeth right now. I found a couple of bugs in the code,
that I fixed, and so far, it is running OK.

Bugs in the code can certainly get you, and they can be subtle enough to
no be noticed on more forgiving material like wax. Have you got any CAD
/ CAM software yet, or are you still hand coding with your modular
routines?

I am hand coding with modular routines.

I have not even looked at CAD/CAM.

I have to admit that I kind of like that, I am in my natural
programming mode of thinking.

CAD/CAM has some advantages in visualizing the part, cutter clearances
and the like, and of course a huge advantage in dealing with machining
operations on complex contours.



If the teeth do not exactly mate, I can file them down with a regular
file.

Only if they're too tight. If they are too loose filing won't help.

Yep.

So, in the end, they were just a bit too large to mate, I filed them
down slightly with a file, and now they seem to mate, though tightly
-- which is great.

The end result is what matters, at least for one off parts.