# Rough edges when milling steel



## turningwheels (May 21, 2020)

Ok, total N00b here. I have a brand new Grizzly G0619 with a max RPM of 1800. When trying to end mill using a .25" end mill HSS TiN, I get all sorts of rough edges. This particular cut was .002 deep at about 5.5 inches per minute. According to my handy (but I am not so sure I believe it) app that shows my feed and speed rate according to the max RPM my machine is capable of. So, what is happening here and why? I am practicing using my new DRO and even the rectangle needed to be shaved of rough burrs. Frustrating to say the least.


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## Martin W (May 21, 2020)

Try slowing your feed rate. Maybe start at 1-3/4” per min and work from there.Is your end mill sharp?
Cheers
Martin


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## Liljoebrshooter (May 21, 2020)

Looks like a dull cutter.  What brand is it?  1.4" in diameter end mill?

Joe


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## Mitch Alsup (May 21, 2020)

My 1+1/2 HP mill G0730 is limited to about 1" end mills and with 1" end mill I use a speed closer to 230 RPMs and use my hand on the travel dial to determine speed of cut, I also look at the surface. I almost always use lubricant--steel=cutting fluid, Al=WD-40.

But, if the ragged edges are from the second cut on that part, the first cut more than likely dulled the cutting edges.


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## turningwheels (May 21, 2020)

Liljoebrshooter said:


> Looks like a dull cutter.  What brand is it?  1.4" in diameter end mill?
> 
> Joe


1/4" inch. I can't type. Grizzly set of end mills. I am starting to see why people spend good money on end mills. I'll try a new end mill that hasn't seen any action yet and report back.


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## turningwheels (May 21, 2020)

I went up to a NEW 3/8" end mill. taking max .01 inch cut on what I assume is mild steel. There are so many variables to this hobby, it's making my head spin. 
However, it's still making ragged edges at 1800 rpm or 850 rpm.
If I do the calculation using the chart from here: https://www.the-carbide-end-mill-store.com/Feeds-and-Speeds.html
420x3.82/.375 = 4277 RPM If this is true, then how do I machine steel with an 1800 rpm limit?


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## Liljoebrshooter (May 21, 2020)

Throw your chart out.  Those speeds and feeds are for production machines that might weigh 10000lbs or more and spindle speeds of 10k or higher.
Most of the manual machines are not rigid enough to do this.  Slow and steady usually does better for the equipment most of us have.
Joe


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## Liljoebrshooter (May 21, 2020)

Also in the first picture you can see the chips don't look like nice chips.  They look like they are from grinding. Another sign of a dull cutter.
Also the grade of steel might not be the best for clean easy machining.

Joe


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## turningwheels (May 21, 2020)

Liljoebrshooter said:


> Throw your chart out.  Those speeds and feeds are for production machines that might weigh 10000lbs or more and spindle speeds of 10k or higher.
> Most of the manual machines are not rigid enough to do this.  Slow and steady usually does better for the equipment most of us have.
> Joe


Ok. It's in the garbage. What is slow and steady for us regular Joe's? Thanks for answering my questions! I know that not knowing what kind of steel I am using has a big impact.


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## Liljoebrshooter (May 21, 2020)

I leave my mill in 440 rpm ( i think) most of the time.


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## Liljoebrshooter (May 21, 2020)

also some good quality end mills will make a huge difference.


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## mikey (May 21, 2020)

turningwheels said:


> I went up to a NEW 3/8" end mill. taking max .01 inch cut on what I assume is mild steel. There are so many variables to this hobby, it's making my head spin.
> However, it's still making ragged edges at 1800 rpm or 850 rpm.
> If I do the calculation using the chart from here: https://www.the-carbide-end-mill-store.com/Feeds-and-Speeds.html
> 420x3.82/.375 = 4277 RPM If this is true, then how do I machine steel with an 1800 rpm limit?



Let me back you up here. You are using a new end mill - is it carbide? If so, then 420 sfm might be okay but if its HSS then you should be using about 100 sfm for mild steel. Using the common formula, that gives us ~1,000 rpm for a 3/8" end mill. However, since we have to take different depths of cut both axially and radially, and we may be cutting either a slot or doing edge profiling, this alters our actual speeds and feeds so a better guide is the one from Niagara Cutter attached below.

For example, you are slot cutting so the entire width of the cutter is involved. Your depth of cut is called your Axial depth of cut and your speed will vary with this axial depth of cut. As you axial depth of cut increases you have to slow down so the flutes can cut. What Niagara has done for you in this chart is to give you different cutting speeds for the axial depth of cut you choose, and it applies to whatever size end mill you're using. Note that this chart is only for HSS end mills; carbide goes faster. 

So, say you chose to go with a depth of cut of 1/8th the diameter of your 3/8" end mill, which works out to a bit more than 0.04" depth of cut. Your speed would be 1120 rpm. 

Feeds can also be calculated but unless you have a CNC or NC mill or a DRO that tracks feed speed, this is not that useful. Most of us will manual feed. What I do is to feed so there is a slight positive resistance to the feed and the end mill cuts just fine. 

Give this a try.


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## Winegrower (May 22, 2020)

When you get the right end mill and work out the best feeds and speeds, there will still be issues.   Check YouTube for a Joe Pie video on how to minimize burrs...he gives tips that may not be obvious when we are starting out.


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## Aukai (May 22, 2020)

I used my Grizzly end mills ONCE.....


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## matthewsx (May 22, 2020)

Liljoebrshooter said:


> I leave my mill in 440 rpm ( i think) most of the time.
> 
> 
> 
> ...



I miss my mastermill, I barely got to use it....

John


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## Lo-Fi (May 22, 2020)

A sensible and hobby machine friendly speeds and feeds calc I've used quite a bit:









						Speeds & Feeds
					

The premier source of tooling, parts, and accessories for bench top machinists.




					littlemachineshop.com
				




It tends to err on the conservative side, which is no bad thing when you're starting out.


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## Janderso (May 22, 2020)

Get yourself some 12L14 steel, a quality sharp end mill, slow down and you will look like a pro.
Some steel just doesn't like to be machined.
Those Asian end mills aren't of the best quality. I learned my lesson on that score.
You only have about 8,000 choices for which end mill to buy.


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## higgite (May 22, 2020)

First, a question for you more experienced folks. OP’s 2nd pic shows a 4 flute end mill. I was taught to use 2 flutes to aid in chip evacuation when slotting. Could that be contributing to the problem?

turningwheels,
1. Have you tried it with a 2 flute end mill to see if you get the same result?
2. In your OP, did you mean .002 deep or .02 deep?

Tom


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## Cheeseking (May 22, 2020)

I have used ME Consultant a freeware feed and speed program for years. . Get’s you in the ballpark.
You can Google and download it.  

1020 carbon steel (assumption)

1/4” dia 4 flute HSS end mill
Start with 100 SFPM 
.050 DOC, .250 WOC (slotting)
RPM=1,528

For feed rate I’d try for .002 per tooth chip load = .008/rev
which is 12.2 IPM 

The cheesy gold HSS end mill isn’t doing you any favors. Trust me. Spend $25 on a 4 flute carbide and your machining life will be transformed. 

Use 4 flutes for steel in most cases.

Use air or a brush to keep the chips away from the cut and prevent recutting.


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## turningwheels (May 22, 2020)

Loads of good info here. Thank you all. Now, if I were to buy some new end mills, what source do you use?


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## Cheeseking (May 22, 2020)

Honestly the choices and variety of cutter materials coatings and geometry available for specific applications is almost infinite. It will make your head spin. 
I have found that McMaster Carr while having a sometimes deserved reputation for being expensive is actually not that bad on end mills. 
Its a crapshoot what exact brand you’ll receive but when we order at work We seem to get YG-1 often sometimes meilin (sp?) 
Can you save a few bucks on eBay ?sure but buyer beware.


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## derf (May 22, 2020)

For smaller end mills I wouldn't even consider HSS for what carbide mills sell for these days.
the-carbide-end-mill-store.com


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## Janderso (May 22, 2020)

derf said:


> For smaller end mills I wouldn't even consider HSS for what carbide mills sell for these days.
> the-carbide-end-mill-store.com


I would agree until recently I noticed chipped teeth on one of my Rushmore carbide 1/2" 4 flute end mills.
I was surprised to see that. I'll have to be more careful with what I mill. Carbide is awesome but it's also brittle. IMHO


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## derf (May 22, 2020)

Carbide is not bomb proof, but given the situation where you don't know what the material is exactly, and speeds and feeds elude you, they hold up a lot better. Even with a chip in one flute, they will cut better than a dull HSS mill. One of the benefits of solid carbide is the rigidity, which will help greatly on a mini mill.


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## Lo-Fi (May 22, 2020)

I love carbide end mills, but they really hate recutting chips. That's what usually chips the edges, all other things bring equal. I use one of the cheap misters, but air only and carefully aimed to evacuate the chips _immediately, _particularly when slotting. 

They don't like chatter much either, and one move from a not so rigid setup will spell the end. 

If you're mindful of those things, they last a really long time and do some beautiful work at insane speed.


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## Janderso (May 22, 2020)

Lo-Fi said:


> If you're mindful of those things, they last a really long time and do some beautiful work at insane speed


Are you using them on a CNC machine?


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## higgite (May 22, 2020)

Cheeseking said:


> I have used ME Consultant a freeware feed and speed program for years. . Get’s you in the ballpark.
> You can Google and download it.



Cheeseking, I wonder why you get .191 HP but I get .134 HP with the same input data? All other inputs and outputs are identical, including efficiency. The link to the user guide doesn't work on my copy, so maybe I'm overlooking something.

Tom


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## Cheeseking (May 22, 2020)

Ya the program has its quirks. There are probably better ones out there but hey its free. I don’t know the answer to why the discrepancy but what I have found is whenever I change a value in one of the boxes, I make sure to click the green box below which updates the values in the other boxes as applicable. Sometimes that has burned me.


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## Tozguy (May 22, 2020)

There is not much you can do with a dull end mill no matter how much it cost. Save any dull mills until you can sharpen them even the cheap ones. If you are only cutting a shallow slot, a shorter end mill would have less deflection. When cutting both sides of a slot simultaneously a 3 flute end mill would be a better choice. It would have been interesting to take another pass to widen the slot on one side by climb milling to see if the burrs still occur.


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## Lo-Fi (May 22, 2020)

Janderso said:


> Are you using them on a CNC machine?



No, just on my bridgeport. Takes some cajones to dial the spindle speed up, but when you do they start shredding steel like its butter. 4 flute 8, 10 and 12mm are my go-to carbide tools. All from Rennie or APT. Sorry neither are too helpful for you US guys! Both seem to be decent quality at very reasonable prices. I've got some HSS mills from APT too, for jobs where I know carbide isn't really suited. Very impressed with the 12mm fine pitch rougher, it's an absolute workhorse. I'd recommend HSS roughing ends mills to any newbie - well worth it for general metal removal, they're much more forgiving than either carbide or plain HSS.


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## markba633csi (May 24, 2020)

I like to use HSS with cobalt roughers for steel, they look like corncobs and last pretty long
Stick with USA made endmills.  I have some tiny ones from China but I don't push them hard, mainly for brass and aluminum
-Mark


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## Reddinr (May 24, 2020)

Just a stupid question.  Is your mill turning in the right direction?  It happened to me and in aluminum the result looked like that.  I had replaced a motor cable with a better one and flopped the phases so forward was reverse rotation.  It drove me crazy for about 15 minutes until I figured it out.


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## turningwheels (May 24, 2020)

Reddinr said:


> Just a stupid question.  Is your mill turning in the right direction?  It happened to me and in aluminum the result looked like that.  I had replaced a motor cable with a better one and flopped the phases so forward was reverse rotation.  It drove me crazy for about 15 minutes until I figured it out.


It's electronic, and it says it's going forward, so I would bet I'm ok. Not a dumb question though.


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## Reddinr (May 24, 2020)

If this mill is brand new to you, I wouldn't assume anything.  Looking down from the top of the machine is the rotation clockwise or counter-clockwise?


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## Cheeseking (May 24, 2020)

I did that once. Insta-smoke the cutter. Have to be careful on BP’s the switch has high and low range and also a high and low gear selector. Mix those up and the mill runs in reverse.


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## turningwheels (May 25, 2020)

So what are common end mill sizes? I'd like to order a few and I have the feeling that bigger isn't necessarily better.


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## Liljoebrshooter (May 25, 2020)

I believe you have the small combo machine.  I would start with some 1/4" and maybe 3/8".
Joe


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## turningwheels (May 31, 2020)

Okay, I got a couple of carbide bits. I feel like throwing the HSS Grizzly end mills out the window. What a difference!
What should I reserve the HSS bits for? Plastic and Wood?


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## Aukai (May 31, 2020)

Are they good enough for that even?  
I'm going to use the box mine came in for real end mills


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