Knee or Quill

That article is addressing knee vs. quill for a CNC conversion. Elrod makes quill CNC Z axis conversion kits for BP type machines. One of the few quill axis systems that can be reasonably switched between manual and CNC operation. Some CNC conversion systems use the knee for the Z axis, this would not be my first choice for a CNC Z axis.

For a manual machine none of this applies. A manual knee or bed mill will still have a quill in all cases.
 
sorry about the CNC article, I am not asking about CNC.

This is what I have learned.
The reason to go with a knee machine is rigidity and better for part positioning.
Quill only machine for size and weight.
 
Submachine said:
sorry about the CNC article, I am not asking about CNC.

This is what I have learned.
The reason to go with a knee machine is rigidity and better for part positioning.
Quill only machine for size and weight.
Click to expand...

A knee or bed mill of similar size will produce the same part within limitations. Normally a knee mill also has a turret head & ram system that allows the head to be moved into positions that would normally not be possible on a bed mill. There are variations on this.

A BP type vertical turret mill is probably the most flexible system as far as being able to make parts that have odd and compound angles. A bed mill of similar weight should be a bit more rigid than a knee mill.

In general the heavier the machine the more rigid it is.

I think you may be confusing the quill with the head that moves vertically. The quill is mounted in the head and moves up & down like a drill press, the head is independently adjustable vertically on a bed mill, and takes the place of the knee. It needs to be said that the larger CNC bed mills have no quill but have a large head travel that provides the Z axis.

All of the bed bench mills that I know of do have a quill, and the head adjusts vertically to provide vertical clearance like a knee. Normally the maximum quill travel is 4 or 5 inches, where the head may be able to move 12 inches or more.
 
I think it was stated above that a horizontal mill with a vertical head will likely have a knee without having a quill. Most of the common vertical knee mills I have seen are basically of the Bridgeport type design that have a knee and a quill. My 8 x 30 mill is a smaller mill with both a knee and quill... I really appreciate the flexibility of having both.

When milling a part I try to keep the quill extension as short as possible for maximum rigidity, especially with larger cutters. For boring a hole I want a quill. A knee mill with a quill gives me a lot of flexibility. Raising the knee is usually a lot quicker and easier than lowering the head on a mill without a knee... at least with the 1 non-knee vertical mill I used.

#1 - What do you want to do with your new mill?

#2 - Are you looking for a manual mill or a CNC mill?
 
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I'm not sure Deckel or the vert head on the Hispano Suiza I saw did either.
 
When I have to do boring the depth governs which I use
I use the knee on deep lengths ( over 5”)
And the quill on short length ( ( up to 5”)
Although my quill will go to 6” I don’t like using the maximum my machine can handle ( room for error).
 
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