Need some advice, end mill selection.

[mdocod]

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

 

[Torque1st]

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.

 

[gadget_lover]

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

 

[larry117]

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.

 

[wquiles]

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

 

[gadget_lover]

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

 

[sawlight]

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.

 

[Torque1st]

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:

 

[precisionworks]

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.

 

[AuroraAlpha]

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).

 

[mdocod]

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

 

[SafetyBob]

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.

 

[mdocod]

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

 

[sawlight]

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.

 

[gadget_lover]

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

 

[SafetyBob]

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.

 

[Torque1st]

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:

 

[sawlight]

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!

 

[mdocod]

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

 

[Atlascycle]

Why not just flat bottom grind a Drill?


Jason