Ok, Rookie Here-- What Am I Doing Wrong?

[JimDawson]

If you are plunging for a slot for instance, then a 2 flute, center cutting end mill would be my choice. The real key here is center cutting. For slotting I would always choose a 2 flute they tend to walk sideways less. Where possible I will first drill a hole for plunging, as you suggest 1/4 inch is good.

PS: +1 What RandyC said above.

 

[Bob V]

I'd defer to Jim for just about all of this but I'd speculate that your end mill is <ahem> not optimally configured at this point Dry cutting is OK if you have the means of clearing chips and keeping the cutter cool. This is my method - maybe not the best but seems to work.

It's just a small air valve and air wand attached to a magnetic base. I adjust the little air valve to obtain a trickle of shop air - just enough to clear the chips from the cutter. It's not good to blow chips all over the place, they tend to end up in places that later cause problems, LOL. The air obviously cools the cutter as well as clearing chips.View attachment 100611

 

[Bob V]

Thanks, Randy. I did notice piles of chips developing around the mill. I had to stop it to brush them away.. My machine has a sump for coolant and motor to pump it, then it drains thru a hose back into a sump in the base--maybe I should hook this up--will have to wire it to the phase converter-- another project!

 

[chips&more]

If you started with an unknown piece of steel you should have set the RPM at the “very” low end. And if using hand feed, listen for problems and look for the not wanted blue chips. And take small/light cuts and use cutting oil until you get a feel for the unknown material and your machine…Good Luck, Dave.

 

[Bob V]

Thanks, Dave. More great advice for a new guy. This forum is great!

 

[randyc]

Thanks, Randy. I did notice piles of chips developing around the mill. I had to stop it to brush them away.. My machine has a sump for coolant and motor to pump it, then it drains thru a hose back into a sump in the base--maybe I should hook this up--will have to wire it to the phase converter-- another project!

You could do that but for most hobby machinists, an acid brush and a little container with some cutting oil (sulphur-based pipe threading oil) from your hardware store works fine. Much less mess ... the brush can be applied to the exact area that needs cutting fluid and chip clearing.

 

[Bob V]

You could do that but for most hobby machinists, an acid brush and a little container with some cutting oil (sulphur-based pipe threading oil) from your hardware store works fine. Much less mess ... the brush can be applied to the exact area that needs cutting fluid and chip clearing.

Thanks Randy. Will go that route first for sure. The you-tube videos I've seen of the coolant flowing does look a mess! I have some "Magic" Cutting oil I use for drilling--maybe that would work for the mill too.

 

[Bob V]

I'd defer to Jim for just about all of this but I'd speculate that your end mill is <ahem> not optimally configured at this point Dry cutting is OK if you have the means of clearing chips and keeping the cutter cool. This is my method - maybe not the best but seems to work.

It's just a small air valve and air wand attached to a magnetic base. I adjust the little air valve to obtain a trickle of shop air - just enough to clear the chips from the cutter. It's not good to blow chips all over the place, they tend to end up in places that later cause problems, LOL. The air obviously cools the cutter as well as clearing chips.

Not visible from this angle but a similar arrangement on the far side provides coolant spray through a wand directed toward the cutter from a reservoir and coolant pump. I rarely use it though - it's a mess and the coolant tends to get stinky after sitting in the reservoir for a few months.

View attachment 100611

P.S. Jim mentioned the resistance to feed increasing dramatically with a dull cutter. That's something that needs to be monitored, even when using power table feed. My personal practice is to introduce the cutter into the work by hand, then feed it by hand for a bit before engaging power feed.

I believe that it's also good practice to disengage the power feed occasionally and check cutting resistance by moving the table by hand. You'll learn by doing ... the "feel" and sound of the cutting process will provide feedback that tells you how the work is progressing

Randy, is that "ball and socket" thing with the black base the magnet? Looks like a great idea. I have air 5 feet from my mill. Do you remember where you got that magnet thing? I recognize most of the other pieces of the system-- but any parts, specs would be appreciated.

 

[T Bredehoft]

Basic rule of thumb, High Speed Steel shouldn't be run faster than 90 surface feet a minute. Sure you can get away with 120, if you're cutting Ledloy, or brass, but for steel, 90 surface (of the cutter) feet per minute is good. A half inch tool then is turning 180 RPM.

 

[Bob V]

Basic rule of thumb, High Speed Steel shouldn't be run faster than 90 surface feet a minute. Sure you can get away with 120, if you're cutting Ledloy, or brass, but for steel, 90 surface (of the cutter) feet per minute is good. A half inch tool then is turning 180 RPM.

Thanks, Tom.
I'll try running the 1/2 inch tool at 180 RPM.
I certainly believe you guys-- you have the hands on experience-- I obviously don't.

I used an online Speed and Feed Calculator at "Daycounter Engineering Services" web site, and plugged in the cutter diameter (.0.5"), and a SFM of 90, and it gives me a spindle speed of 687 RPM.

Also using the formula:
RPM = (Cutting Speed x 4)/Diameter
RPM=90*4/.5=720 RPM

Question: these tables/calculators give speed rates roughly 4 times faster than what is being recommended by you and others.--Can you please tell me why there is such a difference between the RPM's recommended by the tables and the 180 RPM you recommend?

Once again-- having tried the 600+ RPM yesterday with lots of problems-- I certainly appreciate your help and am going to try all your recommendations today.
Thanks!
Bob