# Need some advice, end mill selection.



## mdocod (Aug 30, 2008)

First off, please don't laugh at me too hard here....

I am looking to buy an end-mill set, I've seen a number of sets for under $100 online that contain a nice selection of "normal" sizes, from like 1/4-3/4" diameter. I figure I don't need anything SUPER nice as I'm just cutting plastics.. I can't really afford to spend a lot either, but need a variety of sizes for some prototyping, any suggestions on budget end-mills would be greatly appreciated.

As some of you may know, I've been building battery adapters for awhile, I have some new design ideas that are going to require the cutting of flat bottom holes. So I figured a standard "square" center cutting end-mill would probably be my best bet... is this correct?

Assuming that is correct... I have the option of 2 or 4 flute designs. I've heard that 2 flute end-mills are better for plastics, but am not entirely sure about this.. I figure I'll be using nice slow cutting and "feed" speeds regardless as these will be used in a drill press that isn't as rigid as a true milling machine.

I may also experiment with some side-cutting with the end-mills in the press, I do have one of those cheesy 2 axis moving vices from harbor freight. I've never worked with milling bits, but am hoping that with slow speeds they don't chatter in the press..

Any thoughts or comments on this would be greatly appreciated. 

If it makes any difference, I am primarily working with Delrin (Acetyl Copolymer)

Eric


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## Torque1st (Aug 31, 2008)

Using milling cutters in a drill press can be an invitation to disaster. There is nothing but a friction fit holding a drill chuck into a drill press. The chuck can come loose and do unpredictable things. In the worst case it may kill you. In the best case it just may need to be reinserted. "Drilling a flat bottom hole may be OK but any sideways motion using that X-Y table could lead to severe problems. That said, I have done it and I have been lucky several times but I decided my luck was about out and I bought a mill.


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## gadget_lover (Aug 31, 2008)

Since you are doing plastic, go for HSS end mills, as they will be sharper. 

You can get cheap sets from MSC, harbor freight and other sources. 3/4 of my endmills came from harbor freight in sets. The rest were purchased individually for specific projects.
I don't see any problems with using my cheap HF endmills, but I don't know what top quality endmills will do in a top quality mill.

I've used endmills in a lathe to make flat bottom holes. They work pretty well. You have to clear the chips often. 

I do not remember which is better (4 flute VS 2) but seem to recall the 2 flute will give a cleaner finish, and 4 flute will cut faster.


Daniel


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## larry117 (Aug 31, 2008)

Not sure if it matters or not but an end mill will not leave a perfect flat bottom hole, more like a 3 degree convex shape. 

Most plastic will actually cut better with a higher speed but without coolant you'll have to be careful not to melt it.

2 flutes would work better for plunging to clear the chips, 4 flutes for side milling.


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## wquiles (Aug 31, 2008)

Torque1st said:


> Using milling cutters in a drill press can be an invitation to disaster. There is nothing but a friction fit holding a drill chuck into a drill press. The chuck can come loose and do unpredictable things. In the worst case it may kill you. In the best case it just may need to be reinserted. "Drilling a flat bottom hole may be OK but any sideways motion using that X-Y table could lead to severe problems. That said, I have done it and I have been lucky several times but I decided my luck was about out and I bought a mill.



+1 

I got lucky when I first tried that years ago and I only had to reinsert, but never again. That is why I got the mini mill


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## gadget_lover (Aug 31, 2008)

And if you are lucky, the part you are working on will not be destroyed by the endmill coming loose. When the chuck comes loose the endmill will hit the work at an angle and make some interesting gouges before it comes to a stop.

Daniel


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## sawlight (Aug 31, 2008)

Keep the speeds high, the load light and you should be fine cutting platic on that setup.
Harbor Freight endmills will work fine, I suggest two flute. they clear out better, and will side cut fine.
For plunging they will make a flat enough hole that you and I wont notice the difference.
I have had GREAT luck using Canola oil cutting platics/lexan. It wont stain, and keeps a nice film on the cutter.


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## Torque1st (Aug 31, 2008)

A few times I just had to reinsert. A few times it ruined the workpiece. One time it just threw the part out and hit my hand, -I still have a scar. The last time it pulled the aluminum part out and threw it across the room and broke off the cutter embedding it into a 2x4 wall stud deep enough that pliers were required to remove it was more than enough for me.

Plastic parts come out of the vise or holding fixtures real easy.

Get a mill!!!:thumbsup:


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## precisionworks (Sep 3, 2008)

> I have some new design ideas that are going to require the cutting of flat bottom holes.



IMO, a mill is the best choice. Lacking that, a hand held woodworking router (variable speed) should do a fine job milling/routing plastics. Tool diameters are small, somewhere in the .250" to .500" range, power is limited (which is a good thing in this situation), spindle speeds are many times higher than most any vertical mill & torque is lower - another good thing.

This article from Plastics Fabricator will give you some ideas. Note how router bits look like smaller versions of end mills - both provide the same result. You can't use use a woodworking router in steel, but it is ideal in plastics.

http://www.plasticsmag.com/routing.asp?fIssue=May/Jun-03&aid=3784

The DeWalt DW618D (which I have) would be perfect for bigger jobs:







For smaller jobs, or those requiring finer control, a "laminate trimmer" (palm grip router) would be ideal.






That's the Porter Cable 0310, which weighs under four pounds.


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## AuroraAlpha (Sep 3, 2008)

I would suggest only buying 2 fluted models if price is an issue. The reason I suggest this is that all 2flute models are called 'center-cutting' this means that you can plunge with them, where only some 3+ flute models are. The 4 flute models are very common in both modes. Someone more experienced might be able to suggest a flute angle. Generally you can find a standard (steel) and a high-helix (for aluminum), some people also sell variable helix (also for AL) or ultra-high helix. I have no idea what would cut plastic the best.

As for material I would suggest HSS, coatings are nice but not necessary for plastic. You will probably find TiN coated HSS as the cheapest endmills as they are some of the most common; this is probably your best bet for cheap endmills to be used on plastic. If you are ever going to work with a metal and you want these to be useful it is a good time know because some coatings are ok for everything (TiN) while some are good for aluminum, some cannot be used on aluminum. You could get carbide but you would be wasting your money and they are more likely to chip if dropped.

You can buy individual end mills of extremely high quality from mcmaster.com and choose pretty much everything about them, but they are VERY expensive. You would probably only get 3-6 for $100.

The last thing is just that you never want to use an end mill in a collet if you have used it in a drillpress (unless you consider yourself qualified to find damage). The drill press chuck will have three teeth that bit into, and often damage, the endmill. Putting it in a collet it could wreck the collect itself and your collets are generally some of the more expensive things you own. Also on that subject make sure to pay attention to the flat, you need to make sure that you either clamp above it, or generally a good distance below it. If you clamp on the flat you can damage either the endmill or the collet/chuck.

Ninja edit: The other reason people take 2 flutes is that they have more removal per flute so they jam less. The more flutes you have though the faster you can cut, a 4 flute can cut nearly twice as fast as a 2 in the same exact material, an 8 flute can cut 4 times as fast as a 2 flute. The more flutes you have the better the surface finish for the same cut (depth, force, etc).


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## mdocod (Sep 3, 2008)

Wow, lots of great responses building up here. Thank You all for the input!

I'm torn now about what to do as it sounds like this could be dangerous.. Which is hard for me to imagine considering a rotating speed of maybe 400RPM and everything clamped into place well... But I'm very thankful that those of you who have tried and had strange things happen have reported in here as it will probably keep me safer if I do decide to try this..

Sounds like I'll be going with a 2 flute design 

Eric


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## SafetyBob (Sep 4, 2008)

Eric, if you really are going to get serious about it, look into an adapter from your morse taper #2 drill press (more than likely) to an R-8 end mill adapter. I know funds are tight, but like was stated above, you will have unquestioned holding ability AND safety. 

Go Enco or Rutland....somebody cheap and you should be able to keep this all reasonable. As much as I would like to say get a set, that's up to you, but if you know you need a 3/8 inch end mill for this thing, just get this end mill and be done with it until you need something else. The bad part is you need to be right on your size the first time. 

Bob E.


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## mdocod (Sep 4, 2008)

Hello SafetyBob,

I wasn't even aware such adapters were made...

this is the press I have:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=38142

I've been doing some searching around and am fairly confused because this is all new terminology to me, these "MTs" "30" "40" "50" "R8" "R-8" then lots of "Js" and "Ts" in various configurations with different numbers...

I understand these are all standards for the size of *something* but haven't got all the pieces of the puzzle figured out just yet. 

I assume that the MT2 on my press is talking about the shape and size of the tapered fitting at the bottom of the arbor. I have found that the term "MT2" and "2MT" and "Morse #2" all *seem* to be the same item, which is strange. 

I'm in the process now of searching the net for something that converts a MT2 to an R8 system and have found plenty that do the opposite for folks seeking to use chucks on their mills for those situations where they want to use the mill as a drill, but I'm not finding anything (so far) that goes the other way around... I'm going to continue looking...

What I would like to find is something that replaces the entire arbor rather than just adapts from the Taper fitting as that would be a LOT safer and stronger (is this what you meant in the first place?). My concern is that one of the major safety issues is the taper fitting itself, that is not ideal for any lateral force. 

I really like the idea of having the proper setup for the end mills to be mounted in so I'm going to keep searching the net and try to learn more as I go... hopefully in a few days of reading I'll know enough to feel comfortable making a purchase. 

Thank You,
Eric


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## sawlight (Sep 4, 2008)

No Eric, a taper fitting is not ideal for lateral force. Not sure you will find a Morse to R-8 adapter. R-8 needs a drawbar of some sort to function. But you might find a morse that holds a 3/8"s endmill.
You might be able to find a small flexible collet holder for the Morse tapper and 3/8"s is about as big as they go.


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## gadget_lover (Sep 4, 2008)

You will not find a MT2 to R8 adapter. The MT2 is smaller (physically) than the R8.

It would not be any safer if you did find one. The R8 is held in place with a large, long bolt known as a drawbar. The mt2 in a drill press is just held in place by friction.


Daniel


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## SafetyBob (Sep 4, 2008)

Yup, Eric, I was mistaken. No MT2 to R-8 available only a 3/8 or 5/8 inch holder available through enco Page 447. 

If you were very, very careful and very, very well clamped and if say 3/8 inch would work, you could probably get by. Certainly not the best way to do it. We need to find you a small mill. Or find mill components and have you basically make your own....it wouldn't need to be massive, just strong. 

It is amazing how much metal I can plow through with my old, wiped out Bridgeport. No comparison to the nieghbors sureline lathe/mill setup. I have threatened to build a sureline clone, maybe a little bit bigger, if I do I will make an extra set (couple pieces of aluminum more than likely) and send them to you. 

Bob E.


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## Torque1st (Sep 4, 2008)

gadget_lover said:


> It would not be any safer if you did find one. The R8 is held in place with a large, long bolt known as a drawbar. The mt2 in a drill press is just held in place by friction.
> Daniel


Exactly! There is no drawbar on a drill press to hold the chuck in which is why it falls out when trying to "mill"... :thumbsup:


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## sawlight (Sep 5, 2008)

PM me what you need Eric, I have 3/8" Lexan at work, given specs I might be able to make it easier than you fighting it!


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## mdocod (Sep 5, 2008)

Well, once I figure out a design, I was planning on making a whole bunch, so I need to figure out a solution here, going to re-think my options and the design requirements and look for more solutions 

Eric


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## Atlascycle (Sep 5, 2008)

Why not just flat bottom grind a Drill?


Jason


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## AuroraAlpha (Sep 5, 2008)

Atlascycle said:


> Why not just flat bottom grind a Drill?
> 
> 
> Jason



As far as I am aware no such thing is generally sold; if he’s looking for a cheap solution I don't think he is in a position to grind his own tools.

He is looking for the following (a picture always improves things):





[Though buy HSS and not carbide, also TiCN is probably not the best choice for you here.]

I'm a bit confused though, in your first post you said you just wanted flat bottom holes, which would be perfectly find in a drill press. Do you NEED to be able to cut in the horizontal plane? You might also look at a dremel/grinder/scroll saw/jig saw. All of them will be able to cut plastic and in a much safer manor. All good tools to have in general as well. One other thing might be to get one of the very thin saws and do whatever you need by hand. Very similar to a scroll saw but a lot more elbow grease - also very safe and modestly priced overall.

Edit:
A jewelers saw being one of these:
http://www.amazon.com/Grobet-Jewelers-Frame-Throat-Polished/dp/B0000WTA5Y


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## mdocod (Sep 6, 2008)

I've been thinking about that point- that MOST of what I want to do is just drill flat bottom holes....

However, there is more complication to it than just that, the loading on the cutting tool is not going to be perfectly even, some portions of the hole being cut in the design will be removing material, others will not... if that makes any sense... This is an issue that can cause some lateral forces on the press, which could dislodge the chuck from the arbor. 

I can do without lateral cutting for the most part, I could actually get away with multiple plunges to take care of material removal needed in the design, maybe leaving behind some very minor material that could be removed on a lateral cut without a problem for the press...

I think at this point, I'm just going to give it a try... Going to look for a 2 flute HSS set based on the recommendations thus far and see what happens. I'll keep the speeds down and the loading of the machine to a minimum.


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## mdocod (Sep 6, 2008)

I just ordered a bunch of 2 flute HSS center-cutting mills from enco and actually came out a LOT cheaper than I was expecting to pay based on having looked at other sets online elsewhere... I realize these won't be premium, but for ~$2.49-$5 each I can't complain, for 9 endmills ranging in size from 1/8 - 5/8 inch, plus a countersink bit that I needed (a half-decent 6 fluter), my total shipped is only ~$43. 

Not bad at all, I can afford to screw these up in my chuck without much guilt 

I'll be careful, hehe. 

Eric


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## LukeA (Sep 6, 2008)

mdocod said:


> I've been thinking about that point- that MOST of what I want to do is just drill flat bottom holes....
> 
> However, there is more complication to it than just that, the loading on the cutting tool is not going to be perfectly even, some portions of the hole being cut in the design will be removing material, others will not... if that makes any sense... This is an issue that can cause some lateral forces on the press, which could dislodge the chuck from the arbor.
> 
> ...



If all you want is flat-bottomed holes in soft material, then forstner bits are what you want. They track well because of the rim and go straight down. That rim also cancels out basically all lateral force. In fact, I've seen forstner bits drill holes in material 60˚ from level. That was done with a normal drill press. 

Not any cheaper than the endmills though.


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## mdocod (Sep 6, 2008)

Every forstner bit I've ever seen was for wood. This does not mean that such a bit is not out there that could cut plastic, but just that I have not seen it...

It's actually funny you bring that idea up, as a forstner style bit was the first bit style that came to mind many months ago in my search for a tool that would do this, I spent a lot of time just researching those types of bits and came to the conclusion that it was not a viable option. At that time, I was not even aware of end-mills as the whole world of machining was very new to me. 

Eric


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## AuroraAlpha (Sep 6, 2008)

mdocod said:


> Every forstner bit I've ever seen was for wood. This does not mean that such a bit is not out there that could cut plastic, but just that I have not seen it...
> 
> It's actually funny you bring that idea up, as a forstner style bit was the first bit style that came to mind many months ago in my search for a tool that would do this, I spent a lot of time just researching those types of bits and came to the conclusion that it was not a viable option. At that time, I was not even aware of end-mills as the whole world of machining was very new to me.
> 
> Eric



There are forstner bits for cutting wood, plastics, and metal. They could be a good idea though there are two things to think about:
1. I have only seen bits 1/4th of an inch and larger, if he bought a 1/8th inch endmill, does he need smaller sizes?
2. I have only seen bits with a tip in the center for, well, centering. On a 2 inch bit it really doesn't matter, but at 1/4th inch it will pretty much be half the diameter.


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## mdocod (Sep 6, 2008)

yea that tip in the middle of forstner bits really would be counterproductive, especially if I need to drill a specific size hole in the center of that flat bottom hole with the intention of tapping threads into it and needing as much plastic available for that as possible. hehe.


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## LukeA (Sep 7, 2008)

mdocod said:


> yea that tip in the middle of forstner bits really would be counterproductive, especially if I need to drill a specific size hole in the center of that flat bottom hole with the intention of tapping threads into it and needing as much plastic available for that as possible. hehe.



The tip is basically a nub. A sort of sharp nub.


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## wvaltakis2 (Sep 7, 2008)

Since I just got a new mill I've been watching this thread pretty closely, thanks to everybody for all the information. I don't mean to hijack the thread but while we have the gurus here it seemed pointless to start another thread on endmills...anyway, my question is "What the heck are left-hand end mills really needed for?" My father in law called me with that earlier and I had no answer, I've used left hand drills before but I was stumped on this one. Thanks in advance for your answers. 

~Chip


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## sawlight (Sep 7, 2008)

wvaltakis2 said:


> Since I just got a new mill I've been watching this thread pretty closely, thanks to everybody for all the information. I don't mean to hijack the thread but while we have the gurus here it seemed pointless to start another thread on endmills...anyway, my question is "What the heck are left-hand end mills really needed for?" My father in law called me with that earlier and I had no answer, I've used left hand drills before but I was stumped on this one. Thanks in advance for your answers.
> 
> ~Chip


 

There are two types of "side milling" Climb cutting, and Conventional cutting. Clmb cutting is best left for the CNC's with ultra precise control, very rigid platforms, or a VERY LIGHT clean up pass on a conventional machine.
Climb cutting the flutes are rotating in such a way that it is "sucking" the material into the end mill and loading the machine. Conventional cutting, the flutes are pushing the material away, giving you control with a ball screw for precision.
Now and again you get in a situaion that you cannot get the setup you need, either climb or conventional, with a right handed end mill. That is one reason, there are others.


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## gadget_lover (Sep 7, 2008)

Good question.

I found this on the web:
Left-Hand Spiral - Used for milling multiple layers of thin sheets where chip flow is directed away from work.


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