Milling Plastic

[SpecialtyTool]

I have to put a hole thru 2" of polyethylene and Ive never worked with it before. It calls for a hole to be .440" but it has a plus or minus .060" tolerance. Can I just plunge a two flute HSS 7/16" endmill thru it? I would probly pre drill it and try some different sizes but I would think .060" shouldn't be a problem.

[BenK]

You should be just fine with that just don't go too fast on your RPM.

[SpecialtyTool]

You should be just fine with that just don't go too fast on your RPM.

 

What do you mean by just fine? Id like to hold that dimension as close as I can obviously. How much of the tolerance do you think I would use? I wasn't sure how big to pre drill either. Thought of using the endmill almost like a reamer, just take out a little but I wasn't sure how consistent I could expect to hold the pre drill size.

[BenK]

I would just drill it to size. If you want to use an endmill that will work but with that tolerance a drill would work. With a drill you you could be within .005 without a problem. Like I said keep the RPM lower and feed it about .003-.005.

[Müřlıń®]

The only thing about plastic is it will weld itself to the cutter and could cause the hole to get mangled sometimes.

 

Just be sure you use coolant to keep that from happening.

 

Peck drill it with a 7/16 drill and run with it.

[SpecialtyTool]

I would just drill it to size. If you want to use an endmill that will work but with that tolerance a drill would work. With a drill you you could be within .005 without a problem. Like I said keep the RPM lower and feed it about .003-.005.

 

The reason I didn't want to just drill it is because it is actually two pieces of plastic clamped in a vise and I will be drilling on the seam and I didn't know if my drill would walk. I am actually creating a radius on the side of a part. The part is symetrical so I am doing two at a time. Thats also why the tolerance is so big. It is a .22 radius with a plus or minus .030".

[Müřlıń®]

The reason I didn't want to just drill it is because it is actually two pieces of plastic clamped in a vise and I will be drilling on the seam and I didn't know if my drill would walk. I am actually creating a radius on the side of a part. The part is symetrical so I am doing two at a time. Thats also why the tolerance is so big. It is a .22 radius with a plus or minus .030".

 

In that case definitely mill it. I have done that before in HDEP

[K2csq7]

I don't do plastic but why not Contour Ramp?

Harvey tool has some 2 fluters for plastic, 1/4" tool 2" LOC & lots & lots of coolant.

harvey tool

[SpecialtyTool]

I don't do plastic but why not Contour Ramp?

Harvey tool has some 2 fluters for plastic, 1/4" tool 2" LOC & lots & lots of coolant.

harvey tool

 

Not much to hole on to. Plus this way two parts will be done at once.

[K2csq7]

Keep em together, do both at once. Like you said in the beginning, just use contour ramp (a helix) instead of plunging... maybe I'm missing something....

[SpecialtyTool]

Keep em together, do both at once. Like you said in the beginning, just use contour ramp (a helix) instead of plunging... maybe I'm missing something....

 

Oh. Well its a .220 radius and Im using a 7/16" cutter. Not much to helix. Its the only tool I could find with the right LOC, 2 flute, HSS, and in my price range. (which isn't much )That is my plan for the other bigger radii though. thanks

[Roger Peterson]

PP and PE and very soft, you need to have a very sharp tool with a high rake angle cutting a "thick" chip to get any kind of finish. The harvey tool single flute plastic cutters work very well. "standard" endmills do not cut well, 2 flute aluminum cutters are a bit better but just don't have the rake angle and chip clearance that the single flute endmills do.