How much cutting oil do I really need?

[Kmot]

Hi guys,

I was cutting some steel for the first time on my mini mill. Oh, I have trimmed some t-nuts before, but other than that I have only milled aluminum.

So anyway, I was cutting cold roll steel, 5/8" thick and I needed to mill down 1/4" of it for 6" long by 1.25" wide.

I initially used a 1/4" roughing mill (first time use) and only made a few light passes, working my way deeper and when I was at .030" the cutter snapped in half. So to finish the job and because I was mad I stuffed the largest cutter that will fit into my holder, a 5/8" 4-flute and finished the job. I was using cutting oil and the chips were flying off smoking hot. It looked like a WWII navy air combat movie! ;D

I just kept brushing the cutter with oil because I did not want to burn it out. But when I was finished I had a mountain of soggy, oil soaked swarf. I have never had such a mess before.

Did I over do it? Do I need to constantly be brushing the cutter with oil when I am milling steel? IIRC my deepest cut was .030" but I could definitely feel the pull when turning the wheel on the table.

Thanks!

 

[tel]

I was using cutting oil and the chips were flying off smoking hot.

Sounds to me like you had the speed and/or feed cranked up way too high. I usually cut dry (even on the little X2) with no problems, only use cutting oil when I absolutely have to - mainly because of that mess-making property you have just found.

 

[1hand]

On 1018 0r 12L14 I only take .005 or .010 per pass with am .250 mill on my X3 which is not much, but a little beefier than an X2.

Did you try taking smaller cuts, or stepping your endmill over a little? So your not taking the full width of the bit per pass. When I set up cnc programs, I do a 30% step over, and seems to save bits for me.

Matt

 

[Deanofid]

Hiya Tom;
If you're smoking or getting red chips on an X2, my guess would be you're running the spindle too fast. For the size of the mill, I think you would want to be around 350-500 rpm with a 5/8" end mill.
I'm like Tel when it comes to cutting fluid. Only use it when I have to. I would probably not use any for what you were cutting. Just keep the spindle speed down, and start with a good sharp end mill.
When I do use a cutting fluid, it's usually a few drops rather than a brush full.

 

[Troutsqueezer]

Isn't the idea of a roughing end mill to remove material at an increased rate? Is it something one would want to use on steel on a machine of this size? Just asking, I'm still a rank amateur at best.

 

[kvom]

I use a 1/2" rougher in steel when I need to take off a lot, but that's on the Bridgeport. On a mini-mill it will still cut faster than a standard endmill, but as you discovered going to hard can break them.

The chips in the photo weren't blue, so it's not clear that you were overdoing the feed/speed vs. the material. Whether the mill was up to it is another question.

I usually cut dry in steel and watch the color of the chips. As for cast iron, I'm not a big fan. The resulting dust makes a mess and you need to use low surface speeds. Aluminum is definitely the easiest and cleanest material to machine IMO.

 

[Kmot]

Patience-Patience-Patience

Guess I need some! :big:

Sounds like I was spinning too fast and cutting too deep. I really do like the idea of not creating that mess. I will just have to slow down.

Odd, but even at the rate I was cutting it took about four hours to machine that piece on both sides. Yes, I overlap about 50%.

Thanks fella's!

 

[picclock]

It sounds to me like it was a very hard piece of steel. I normally use hot rolled cos its cheaper and stress relieved and a bit softer. If its as hard as it appears you could anneal it (which would de stress it) or alternately use a large carbide cutter. They cost quite a bit but you can't beat them for harder steels, and you can also run them at higher speeds. However those little chips burn at every opportunity. I have a leather apron and the little blighters still seem to get me .

For lube on steel I normally use a brush with cutting oil (tried all sorts generally motor oil seems to work as well) or an old oil can to try to get lube on the cutting area. If it gets too hot the tooling will lose its edge and end up as scrap. For a fine finish on steel try lard (apply just before finish when metal is hot enough to melt/soften it or the lumps go everywhere). Flycutting with lard is an experience to behold and you get free redecoration thrown in ;D .The lube does make a mess but for me its that or replace tooling.

Bogs gets cutters from richontools, and I have for some time. If you work metric a 3/4" carbide 4 flute will fit into a 20mm collet but would cost £22 (20mm HSS 4 flute £3.90) however the 3/8 inch carbide (10mm) work out at £3.90 plus carriage.

I think if it was me, I'd anneal it before it broke any more of my tooling.

Best Regards

picclock

 

[bambuko]

Notwithstanding perfectly sound advice about speeds etc - I see nothing wrong with the picture you have attached to your first posting. Just an honest machine with swarf and cutting oil
I like using cutting oil - after all it's a workshop and it gets dirty ;D
Unless that is, you have your machines in your living room or bedroom :big:

Chris

 

[Kermit]

use some newspaper(remember those?) or paper towels, and lay down a drop cloth arrangement.

When you are done you carefully pick up the pieces of paper and throw them and the majority of the swarf in the trash.

Leaving just a little dusting in odd corners for you to hit with a vacuum.

 

[Ken I]

There's nothing wrong with making a machine work and I don't see the point of ending up with a pile of finer cuttings of the exact same mass of larger ones - other than they took a lot longer to produce.

Burning up perfectly good cutters or wearing them out faster because of lack of lubricant is another matter - so I lubricate when machining steel, cast iron and aluminium - I only cut brass and bronze dry.

I typically apply oil with a brush like yourself and live with the mess.

My secret weapon is a turbo vacuum cleaner parked permanently above my lathe / mill.

It relies on a cyclonic action and is unperturbed by wet chips.

Ken

 

[Kmot]

I have been trying to think of an idea for a 'spash shield' of sorts that would fit around the perimeter of the mill to contain the flying bits. Newspaper might just be the ticket! I am not averse to using cutting oil, I just wondered if I used too much, or in other words more than was needed. I was basically flooding it constantly with the brush. ;D

 

[Ned Ludd]

Hi Guys,
There is a school of thought that says you should not use cutting "oil" when milling but soluble cutting fluid. The reasoning goes that the chips stick to things with oil (not good) and there is little cooling effect. Whilst a constant flow of water based soluble fluid washes the swarf away and has a much greater cooling effect.
Chips sticking to cutters and work is bad because they can adversely effect the finish you get.

Ned

 

[Ken I]

I would have to agree that soluables are better at cooling but unless you have a full on sump / pump etc are not terribly practical on mini lathes and mills.

Appreciate the point about bits sticking but I can't say I've found that to be much of a problem. Quite the reverse - if I'm having a finish problem thats normally an indication to add oil.

As per usual it depends on any given set of circumstances.

Ken

 

[Kmot]

Perhaps I used the wrong term. Not cutting oil, but cutting fluid is what I use. Tap Free to be exact.

 

[Metal Butcher]

Perhaps I used the wrong term. Not cutting oil, but cutting fluid is what I use. Tap Free to be exact.

The first in the line-up is cutting oil. Is that what your are using? Oil and fluid are interchanged on their site.

http://www.tapfree.com/productinfo.html

-MB

 

[Metal Butcher]

Hi guys,

I was cutting some steel for the first time on my mini mill. I was using cutting oil and the chips were flying off smoking hot. It looked like a WWII navy air combat movie! ;D

I just kept brushing the cutter with oil because I did not want to burn it out. But when I was finished I had a mountain of soggy, oil soaked swarf. I have never had such a mess before.

Did I over do it? Do I need to constantly be brushing the cutter with oil when I am milling steel? IIRC my deepest cut was .030" but I could definitely feel the pull when turning the wheel on the table.

Thanks!

Did you over do it? Only you can answer that question. The result of over doing it is just more oil to clean up. I use as little as possible for that reason alone. One drop to drill one hole. One drop spread on a square inch of surface to be milled. Apply oil as a one shot deal to the material and not the cutter before you start milling. The oil will get to the cutting edge. Stay away from adding it to a spinning (or stationary) cutter. Adding to a spinning cutter is asking for trouble, and adding it to a stationart cutter results in most of it getting thrown off by centrifugal force.

You could feel a pull? Are you using a climb cut? If so than I recommend that you discontinue this practice. Use a conventional cut only. On the rare occasion when I use a climb cut to finish up, my limit is a .001" (one thousand of an inch) cut.

You said that you broke a 1/4" roughing cutter? I learned the hard way, and broke every think imaginable! And a few unimaginable! The only way that I can think of to break a cutter that large, would be to run it it into the work way too fast and bend it over to the point of breakage, or to attempt a full climb cut. The cutter will grab in, climb up, bending the cutter till it snaps in two. The latter is so quick and easy.

I don't presume that you don't know what you doing, or don't know what I'm talking about, the purpose of the link provided below is to benefit any beginner that reads this thread.

http://web.mit.edu/2.670/www/Tutorials/Machining/mill/Description.html#5

-MB

 

[Kmot]

I was cutting in a rectangular pattern so it was climb cutting in one direction.

The Tap Free I have is an older metal can and does not look anything like the plastic bottles they show on the website. I will have to go read the label later. I can't remember if it says oil or fluid.

The roughing cutter was 3/8" shank down to 1/4" cutter and I have read lately that those tapered down types are easily broken.

 

[Metal Butcher]

I was cutting in a rectangular pattern so it was climb cutting in one direction.

The Tap Free I have is an older metal can and does not look anything like the plastic bottles they show on the website. I will have to go read the label later. I can't remember if it says oil or fluid.

The roughing cutter was 3/8" shank down to 1/4" cutter and I have read lately that those tapered down types are easily broken.

Kmot, If by "rectangular pattern" you mean that you went back and forth along the same plane, then yes that would be 'climb milling' on every other cut. If you milled all the way around it could have been either 'conventional' or 'climb milling' depending on the direction of the tool travel and your starting point.

Whether the can says oil or fluid doesn't really matter. The only reason I mentioned it is that you thought you termed it incorrectly, but you didn't as far as I'm concerned. A cutting fluid can be oil, lacquer thinner, kerosene, goats milk, or a water based coolant, just to mention a few.

The larger shank diameter would not have any bearing on reducing the strength of the cutter, the shank diameter would have a bearing on the strength of the cutter if it was smaller than the diameter of the cutting face. In that case its possible, if the speed and feed were maxed out based on the larger cutting diameter.

To reduce the entire thickness of a steel plate, a carbide tipped tool bit mounted in a fly cutter might be a better way to go.

-MB

 

[Kmot]

Thanks MB.

Okay, my bad. The stuff I am using is called "Rapid Tap" cutting fluid, and it comes in a red and yellow can.