Milling with the quill extended

[hornluv]

I keep seeing pictures and videos of people milling with the quill extended, including a shot in the latest issue of HSM (July/August 2010, Page 22, Photo 5), in which the quill looks to be almost all the way down and the lock may or may not even be tightened. I've always been of the impression that the quill is for drilling, not milling, and I teach my students such. I don't even like to use an edge finder with the quill extended. What are your thoughts?

[oldbikerdude37]

The quill needs to be realed in to be ridged, thats a standard deal.

[KINGWELD]

Stuart, I'm with you on this. Keep the quill up and you maintain more rigidity which helps everything out(including the machine). Isn't this how it is taught in basic shop??(was for me)

[boslab]

I keep seeing pictures and videos of people milling with the quill extended, including a shot in the latest issue of HSM (July/August 2010, Page 22, Photo 5), in which the quill looks to be almost all the way down and the lock may or may not even be tightened. I've always been of the impression that the quill is for drilling, not milling, and I teach my students such. I don't even like to use an edge finder with the quill extended. What are your thoughts?

You are spot on right sir, I saw a vid on youtube of a flycutting operation with a bar cutter, not a disk, unbalanced. the vibration was clear as tins were rattling on a shelf, and the quill was at 3/4 mast!, it was reflected in the surface finish well, as well as being potentially dangerous.
I wont even consider that much projection on my 3 ton Cinny whos quill is about 6" diameter, never mind a [pos/sir john] Bridgeport.
mark

[KiddZimaHater]

Yes, side milling with the quill down is a big no-no. It can damage the bearings, or worse - tweek the spindle just enough to bind things up.
I always mill with the quill up & locked, and only use the quill for drilling.

[Forrest Addy]

Let's keep a sense of proportion here. Hard and fast rules are often counter productive. GENERALLY, you choke up on the quill when milling, GENERALLY extending for drilling, boring, etc.

The time to keep the quill houses in the head casting is in heavier side cuts however, light cuts with the quill extended a proportonate distance pose no threat to machine or process.

I have a 2" face mill that uses round carbide inserts to chomp off scale and hard steel. It's a real war club. I suck the quill all the way up and lock it when I use it. Vibration is often severe and extending the quill not only promotes vibration but threatens the skinny spline connecting the spindle to the head pulley. Another point is plunging into the solid with a "ground to center" endmill produces large gyratory forces. These are better fed with the knee with the quill fully housed or better yet pre-drilled. Just because a mill is center cutting doesn't mean it's a good idea to use that feature on a limber turret mill.

I might extend the quill when I use smaller shell mills for facing and light side cutting. I might extend it a lot when cutting small details or slots with small endmills.

Every job is different and every cut needs assessment as to the cutting forces, their direction, the action on the work, deflection of the cutting tool, the working parts of the machine, and so on. A good machinist does this at a glance hardly aware of the process. Noobs and the lesser experienced have to formalize this assessment process even to the point of diaaling the cutter to the work and visualizing the forces and deflections.

But please, hold off on "quill is for drilling; knee is for milling" level of orthodoxy. Such statements tend to harden into somethng like superstition. A machine tool's features are there to be used preferably wisely, but still, used to best advantage.

[John Stevenson]

First off ask yourself
"Am I in high production mode ? does the last nano second count ? "
If the answer is no then back off a bit and treat the machine nice unless it's a POS Bridgeport.

Think about this many mid sized CNC machines use the quill for everything and they don't have the advantage of a quill lock, they have been around for years, produced more parts than the average Joe in his home shop can even dream off and had to produce many parts that pass inspection greater than home shops weld where it fits tolerances.

I often have to have the quill further down than I would like so the head casting isn't hitting projections on the work. Using the knee in a case like this isn't an option.

.

[Timleech]

Yes, side milling with the quill down is a big no-no. It can damage the bearings, or worse - tweek the spindle just enough to bind things up.
I always mill with the quill up & locked, and only use the quill for drilling.

How can it damage the bearings, don't understand that one?
Yes of course the quill projection needs to be at a minimum for heavy side cuts.
With my machine it's not always possible to mill with it fully retracted, never really a problem though.

Tim

[John Stevenson]

I wondered on that one Tim.
Must use different sized bearing when its down than when it's up or perhaps it's when it's up it's different from when it's down ?

.

[Your Old Dog]

I would think the bearings would endure more force with the quill extended.

I don't have a knee to play with on my mill/drill but I work more aluminum for ease then steel. When planning on heavy cuts I put my shoulder through the abuse of lowering the head to the work.