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Milling steel

Hukshawn

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#1
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.
 

mikey

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#2
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.
 

HBilly1022

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#3
Have you got a link to those tables? I'd be interested in them too and must have missed that post.
 

Hukshawn

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#5
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...
 

Hukshawn

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#7
Dammit, you beat me to it... I was just searching for that thread. Lol
 

Hukshawn

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#8
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....?
 

jocat54

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#9
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.
 

mikey

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#10
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.
 

mikey

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#12
I just remembered that when I cut my tool holders down, I used my inserted carbide fly cutter and shaved them down. If you want to use an end mill, use the 1/2" one and run at about 400-500 rpm. Try small cuts and work your way up. By small, I mean 0.025" deep, and increase if that goes well. Be sure you conventional mill it.
 

Charles Spencer

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#14
I've got a mini mill. Before I got lucky and bought a large batch of US end mills, I bought a couple of sets of cheap Chinese end mills, viz:

http://www.banggood.com/10pcs-HSS-4...Straight-Shank-End-Mill-Cutter-p-1076080.html

For the money they work very well. And if I screw something up I'm not going to cry over them at that price.

They have free shipping to the USA, don't know about Canada.

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
It might be better to grind off most of the excess and finish it on the mill.
 

Ken from ontario

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#15
Shawn,we both have realized that this hobby is going to be an expensive one.
The moment I think I have the right tools for a job, I find another tool that would be more proper and better :mad: , then I convince myself,this is, it get it and you can do most basic tasks which is never true,there's always a tool I want to get,always.

If it makes you feel any better about milling MS with a mini mill, I'd say I felt the same way at first but found out I was too worried for nothing, this is how I made it work for me:
I don't use any end mills bigger than 1/2", don't remove more than .020" in each pass(.010" is even better),always lock the axes not in use. use cutting oil liberally. find the right RPM/the sweet spot for the diameter of the end mill.
Another item you should think of buying:) is, a portable metal cutting bandsaw , it helps to remove most of the material before you even get to milling it, a roughing bit is also a must have, it removes mild steel almost as quickly as aluminum.
I myself don't have many tools but I do have a Portaband bandsaw, you're welcome to use it.
If the vibration of the milling machine is too much , try to evenly bolt it down or somehow anchor it to a stable surface.
That's all I can think of for now.
 
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Hukshawn

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#16
I've got a mini mill. Before I got lucky and bought a large batch of US end mills, I bought a couple of sets of cheap Chinese end mills, viz:

http://www.banggood.com/10pcs-HSS-4...Straight-Shank-End-Mill-Cutter-p-1076080.html

For the money they work very well. And if I screw something up I'm not going to cry over them at that price.

They have free shipping to the USA, don't know about Canada.
Holy moly those are cheap!
Free shipping here too. Usually is from China... somehow...
 

kramynot2000

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#17
If it makes you feel any better about milling MS with a mini mill, I'd say I felt the same way at first but found out I was too worried for nothing, this is how I made it work for me:
I don't use any end mills bigger than 1/2", don't remove more than .020" in each pass(.010" is even better),always lock the axes not in use. use cutting oil liberally. find the right RPM/the sweet spot for the diameter of the end mill.
Another item you should think of buying:) is, a portable metal cutting bandsaw , it helps to remove most of the material before you even get to milling it, a roughing bit is also a must have, it removes mild steel almost as quickly as aluminum.
This is similar to what I've recently started doing when I made the jump to milling steel. I primarily use endmills no larger than 3/8 and have a shallow cut, .010-.015. Also, I got a portable metal cutting bandsaw, mounted it vertical in a stand, and try to take as much off with that before going to the mill. I'm probably being too conservative, but up until a couple months ago all I milled was delrin or aluminum. Still trying to get comfortable with steel.
 

Hukshawn

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#19
Thanks guys. All good info.
I'm currently trying to mill down that insert tool holder... noisy as all hell...
Using a carbide fly cutter as I think I'm work hardening as I go...
I tried using that 1/2" end mill and pretty sure I pull a dull spot on it. Super thrilled about that...
 

Four Corners

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#20
I have only been playing with my LMS mill for a couple of months, but I'm impressed by what it can do. Sure, it's not a Bridgeport, but it can still cut. Having said that, I've totally ruined the ends of two of those cheap, gold end mills that come in sets. I was trying to cut slots in MS, and I got it all wrong. For one thing I was running them at warp factor 9 (don't know why, because I've watched enough YouTube to know about feeds and speeds tables) and I misunderstood something very important. There's so much talk about 2 flute and 4 flute end mills. 2 flute for aluminum, 4 flute for steel. Right? Well, back in my old country (the UK) the 2 flute end mill is called a slotting mill; it's used for cutting slots. 4 flute end mills tidy up faces and ends. When I turned the mill down so slow that I could almost hear the individual cuts (but not quite), used the 2 flute mill (that I bought to replace the one I messed up) and I bit of some oil I had lying around, my little mill chomped through the 4140 like it wasn't there. There were razor sharp needles flying everywhere.

So, go slow, and give it a go. The cheap end mills are plenty good enough in the right hands.
 

Four Corners

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#21
Following on from that.... I bought a super cheap fly cutter set ($20 Canadian) and an even cheaper brazed carbide lathe tool. Unbelievable finish on steel, aluminum and brass. Honestly, it's almost like a mirror. I spent some time tramming the mill (see Stefan Gotteswinter's vid on that. I used JB Weld) and I'm very happy. It's not really very noisy at all. I wear hearing protection anyway though. Just coz being deaf isn't much fun.
 
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