Has anyone done

[Privateer]

any type mill work in a drill press?

[Insanity]

I have not but I have been told that a DP is not suited to handle the side loads a mill sees.

[mikeyb]

any type mill work in a drill press?

Attempted, yes.
Well before the attempt I was told by a seasoned machinist that results would be poor and that it could be dangerous.

I have:
a pretty sturdy drill press... when compared to other drill presses
a solid X-Y table/vise which I spent time smoothing and adjusting to remove runout
some nice SHARP 4-fluted end mills

What the seasoned machinist told me was accurate. My drill press lacked the stiffness/rigidty for proper milling operations.
Very light cuts in SOFT materials (plastics) did work.
Aluminum milling was rough and dangerous. Won't even attempt to mill any harder materials.
I modified one drooper rail by drill press milling.
For the second drooper rail mod I used a cutoff disk and some hand files. Modifying rail #2 was actually faster and after filing both parts looked about the same.

I still have all the tools but have decided that I won't use the drill press as a mill again for any material harder than plastic.

[KWK]

Drill presses usually utilize a short JT 33 Jacobs taper to attach the chuck which can not handle side loads. Your chuck can pop out and go spinning around like a top with a nice sharp endmill chasing you around or maybe landing in your lap. OUCH! Bloody ouch!
Even if you have a drill press with a Morse taper spindle like one of mine does the whole machine is not rigid enough to do much of any milling. The bearing are designed to handle thrust loads. Not side loads.
It's also not recommended to hold an endmill in a drill chuck even on a milling machine. Same issue, the chuck is attached to the R8 shank by a JT 33 taper. Always use an endmill holder or a collet.

[Back_Roads]

 I found this best for metals, " I used a cutoff disk and some hand files. Modifying rail #2 was actually faster and after filing both parts looked about the same."

[JuryRigger]

KWK nailed it-and yes I've tried and yes the chuck did come off and no, thankfully no blood was drawn 
However-if you happen to have a rotary tool, and a decent XY table, you could probably jury-rig for some cuts using either burr bits or cut-off wheels (this I have done on a very limited scale)...
Jesse

[Motorhead]

One is a DRILL ... Other is a MILL
While a mill can also drill, a Drill is not suitable as a mill 

[Privateer]

One is a DRILL ... Other is a MILL
While a mill can also drill, a Drill is not suitable as a mill 

Good thing to remember!

Now I really don't want to try the side feeding of a part.
How about a face cutter bit? I have an clamp for the drill press that allows me to hold parts at an angle.
I'm thinking I could do a slow plunge cut type thing since that would be straight down.

The part has the Air Gauge that I want to relocate from the bottom to the side with a slight angle.
I was thinking to plunge a face bit and then drill and thread the thing.

Or would I be better off setting up the lathe for something like this?

@Scott,
 You may be familiar with this part. It's the RainStorm 1 block where the air gauge screws in.

[JPSAXNC]

The big danger of running an end mill in a drill press, is that a drill chuck will loosen up from the vibration and the end mill will snag and break and or fly out.

[WhatUPSbox?]

Also tried this and gave up. In addition all the problems mentioned, unless your drill press has fine Z axis control, plunging is frustrating and sketchy.

[KWK]

One is a DRILL ... Other is a MILL
While a mill can also drill, a Drill is not suitable as a mill 

Good thing to remember!

Now I really don't want to try the side feeding of a part.
How about a face cutter bit? I have an clamp for the drill press that allows me to hold parts at an angle.
I'm thinking I could do a slow plunge cut type thing since that would be straight down.

The part has the Air Gauge that I want to relocate from the bottom to the side with a slight angle.
I was thinking to plunge a face bit and then drill and thread the thing.

Or would I be better off setting up the lathe for something like this?

@Scott,
 You may be familiar with this part. It's the RainStorm 1 block where the air gauge screws in.

A milling attachment for your lathe is a possibility. They're not the best but better than trying to do it on a drill press.