Milling steel

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Hukshawn

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so far all I've been cutting on the mini mill is aluminum (I made the belt drive conversion kit)
I've got some steel I want to mill down, but honestly, I'm nervous....
I have two end mills that I've been using. 1/2" 2 flute I've been mainly using that was brand new, and a 1/4" 4 flute I had in the tool box I bought that was still sharp. (And a few smaller ones that are still sharp too).

What are you guys using to mill (mild) steel? What's your usual doc? I'm afraid to ruin an end mill. Not because they cost money, but really, because they're a pain for me to get... but I'm not opposed to getting a couple more more suited to steel over aluminum tho.
I know I need to get a roughing end mill, but I'm really looking for guidance here to get into machining steel...

I know, now that I've broken in the mill somewhat, I need to readjust and tighten. It vibrates/chatters a bit when cutting.
 
Shawn, remember those tables I posted for you awhile back? Have a look at them and they'll tell you what you need to know.

For example, look at the table for mild steel. Let's assume you're using a 1/2" dia., 2 flute finishing end mill to cut a step or rabbet in 1018 mild steel. Basically you need to know what speed to use for a given depth of cut and that is what the table tells you. Say you want to take a 0.06" deep cut: 1/2" / 8 = 0.0625". The cutting speed for this material in the table with that depth of cut is 160 SFM.

Now, 160 X 3.82 (or 4 if you like to round off) / 0.50" = 1222.4 rpm, or about 1200 rpm.

So, set your axial depth of cut in Z to whatever you want (no more than 1.5 x the OD of the end mill), then set your depth of cut in X or Y, depending on which surface you're cutting, to 0.060" and adjust your speed to 1200 rpm. Now make the cut.

Most of us don't have a way to precisely control feed so you'll have to feel and listen to the cut. There should be a slight positive resistance to feed and a hissing sound when the cutter is cutting well. If you do have a way to control feed precisely, then the chart also gives you the feed per tooth so you can plug it into the formula: FPM = f x T x rpm, where f = feed per tooth, T - number of flutes and rpm is, in this example, 1200. The result will give you the feed rate in inches per minute.

You can adjust feed rate, speed or depth of cut to suit the results you're seeing during the cut. Give it a try.

Hope this is clear. If not, shout out.
 
Have you got a link to those tables? I'd be interested in them too and must have missed that post.
 
Mike, I do have the tables. But I know those are likely for a full size (or mid size) mill. On this mini mill, it feels like trying to cut rocks... I know this is a versatile mill, but it feels very fragile and delicate... I'm honestly looking for one of the mini mill guys to "talk some sense" into me and give me their "go to's" and regular practices...
 
Dammit, you beat me to it... I was just searching for that thread. Lol
 
This site is my comfort zone now, it seems... I come here when (not just when I'm bored...) I'm unsure about something. I can usually sort out the issues on my own, but often it's just helpful for someone to agree with me, or use them to bounce ideas off, or really, just to talk it out. I feel very at home here..... now I'll put my purse away... the guys who have had the mini mill years longer than I have likely have regular practices for milling harder than aluminum materials, I want to know what those are.

I have a insert carbide tool holder for my lathe that's a 3/4x3/4 shank. My qc tool holders are 1/2" max. I want to mill that shank down to 1/2" and use the tool. I tried using the 1/4" 4 flute and did a bit of a test and it was like grinding rocks.... I swear the end mill IS sharp... is that just how it's gonna feel....?
 
Shawn, I had the Grizzly mini mill and you will be surprised what that little mill will do, especially with the belt drive on it. You are right about getting some roughing end mills, really helps on the mini mill.
 
If it makes you feel better, I used those tables to guide my cuts on my Sherline mill and on my larger mill/drill.

As for cutting a tool holder, it is probably hardened or at least case hardened. You might want to try a carbide end mill on them.
 
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