Question on mill cutters

Pmedic828

Pmedic828

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Hello everyone - i am attempting to learn and have little experience. The question is what type of mill cutter (End Mill) should i start out with.
I don't understand the difference between HSS and Titanium HSS? Is it better to purchase HSS end mills to start off with? What about the number of flutes 2 or 4? How does a roughing and a finishing end mill differ? Should I go directly to some type of replaceable carbide end mill? Please give me some options and explain why one would be better than another and what type of job would you use these for?
 
828,

You'll do fine starting out with HSS cutters. Titanium is actually Titanium Nitride (TiN), a coating that helps it last a bit longer and avoid sticking. They do cost more, so you'll have to decide. I use both.

2 vs 4 flutes depends mostly on what metal you will be cutting. For steel, a 4-flute endmill will allow double the feed rate compared to 2-flute. For aluminum, you will have a faster RPM and a faster feed rate, so the 2-flute endmill is necessary to allow for the chips to be cleared more easily.

There will be times when you move too fast or climb cut at the wrong time or get the RPM too fast and you will take the corners off an endmill. It happens. It's called learning. We've all been there and we all will be again. Normal HSS endmills cost less, but still do a good job. I recommend starting with those. When you're getting more comfortable with milling, start trying other options.
 
I recommend starting with cheap, uncoated HSS endmills. 4 flute for steel, 2 or 3 flute for other stuff. Using the cheap stuff while you are learning makes it hurt less when you break one in half because you hit the wrong lever at the wrong time. Buy a half dozen in the sizes you expect to use. Endmill size depends on the size of your machine. For a minimill, you probably don't want to go much over 1/2". I like 1/4" and 3/8" even on my knee mill. For heavier material removal or truing up larger surfaces, I use an indexable cutter or a fly cutter. I have had the indexable cutter for some time, and it never worked well on my X2; the fly cutter was much more effective on that machine.

Something like these [uel]http://www.use-enco.com/CGI/INSRIT?PMAKA=320-0060&PMPXNO=2603726&PARTPG=INLMK32[/url] as an example of a 2 flute. They are on sale right now as an added bonus. These are not really high quality, they are not going to last as long as carbide, or cobalt endmills, but it's likely you are going to break them before you dull them. Just accept it's going to happen, and try to understand why it happened when it happens. One thing to keep in mind is that 4 flute endmills can be either center-cutting, or non-center cutting. Center cutting means that you can plunge straight into the material like a drill. This is not possible with a non-center cutting end-mill unless you drill a clearance hole first; Keep that in mind when you are buying/using 4flute endmills. 2 and 3 flute endmills are always center-cutting.

If you can get a good deal on a name brand endmill, or a coated endmill, then go for it.

As far as roughing endmills, they are intended for roughing passes, specifically for removing lots of material. The edges are serrated, which results in smaller chips that are easier to evacuate. They leave a rough finish though, so usually they are used first, leaving a bit of extra material, and then a finish endmill is used to machine to final size. I have a couple, but I have not tried them yet. They can speed things up, but you don't need them.
 
It really all depends on the material you are cutting. HSS works fine on aluminum but I prefer Carbide when cutting Steel, A36 or A572-50, it last longer and you can take heavier cuts.
 
I second starting out with HSS, chose one of the less expensive ones from Enco, Shars, etc in a 4 flute (a 4 flute will still do nicely on aluminum). The other repliers have pretty well covered them, but one thing I would like to stress in starting out on the mill is to slow down, if you think youre going slow enough, youre probably not! Its usually THE one thing a newbie has problems with - I certainly did. Too fast a rpm and too fast a feed will not only cause breakage (as mentioned) but (I think) will more often fry the cutter. I burned up way more EM's than I broke til I learned to control speed/feed.
 
The most cost effective end mills to buy for just someone just starting are two flute and four flute double-end end mills.

Don't waste your money on coatings, they only add extra cost to the end mills and you won't be able to tell the difference between a coated and un-coated end mill in use. Use the two flute end mills for non-ferrous metals like aluminum and brass because they have lots of chip clearance and won't plug up as easily, and the four flute end mills for steels and stainless steels, because they are stiffer have a lower chip load on the teeth.

Stay away from carbide. I know it's considered the best thing since sliced bread on these forums, but it is not appropriate for a new machinist on a steep learning curve. When you get some experience under your belt, can calculate speeds and feeds and learn how to use an end mill without breaking it or burning it up, THEN look into carbide. Carbide end mills are expensive and unforgiving for the new user. You drop them, they are toast; push them too hard, toast again, and when a carbide end mill breaks, instead of losing $5 to $10 bucks, you'll lose $15 to $20.

Buy good quality American or European made end mills. The cheap Chinese imports are useless. The steel is low quality and the geometry is worse. Look for brands like Niagara, Weldon, Brubaker, Morse, etc. Yes, you will pay more initially for a name brand end mill, but it will long out last a cheap import and it will produce a better finish. Quality tools are worth the investment, especially when it comes to cutting tools.

Tom
 
I vote for cobalt HSS, with coating. They are under $10.00 and they can take more punishment on feed than carbide, but far less heat, so if you just dont spin them really hard, they are in cases better than carbide, because you can bite deeper. Im giving a course in CNC on cnc in your home forum. I will cover how to calculate feeds and speeds on end mills in the near future so you stop burning or breaking them, I will teach how to tell you are going fast, and when to change endmills to leave the old for sharpening.

regards.
 
Syaminab said:
I vote for cobalt HSS, with coating. They are under $10.00 and they can take more punishment on feed than carbide, but far less heat, so if you just dont spin them really hard, they are in cases better than carbide, because you can bite deeper. Im giving a course in CNC on cnc in your home forum. I will cover how to calculate feeds and speeds on end mills in the near future so you stop burning or breaking them, I will teach how to tell you are going fast, and when to change endmills to leave the old for sharpening.

regards.
Click to expand...
Just finished with the feeds and speeds theme for endmills on cnc course. Hope it helps you cut better
 
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