The Leading Manufacturer Of CNC Knee Mill Retrofit Hardware and Retrofit Kits  


Knee Mill Or Bed Mill?

Competitors watered down Machining Centers with handles called "Tool room mills" is not the answer! 

The knee mill either manual or CNC is the most versatile machine tool you can have in your shop.

The knee mill is a perfect tool for prototype work and R&D work as well as every day machining.

Versatility is the key, your expertise in setups can enable you to do practically any milling operation on a knee mill (see pictures at the bottom of this page, we continue to add them as we receive more).

Some things to consider when deciding which type of machine to purchase or retrofitting an existing knee mill.

  1. Angular setups no problem, as well as compound angle just swivel the head and tram it into a sign bar to insure your angle is correct.

On a bed type mill you have to purchase an expensive sign plate or a tilting rotary table with a trunion fixture.

  1. Large plates no problem, position the plate on the table and when your travel has been exceeded swivel the turret and extend the ram and pick up a known spot on the plate to continue your operation.

On a bed type mill you have to move the part to continue your operation. As you know moving the part can be disastrous to your positional accuracy.

  1. Machining long parts on a knee mill can be performed by swiveling the turret and hanging the part off the table with an angle plate or your vise

(If you own a vise that can be turned and clamped on its side)

On a bed type mill you only have one option, that is a tall angle plate to hold the part against while machining the end. That is if you still have enough Z travel on the head to clear the part.

  1. Knee rock or Table sag , these terms are used when the X travel is extended to extreme limits. The new larger size knee mills have this taken care of with massive box ways on the saddle and box ways on the knee (on some makes). This condition only happens when the machine is considerably worn. A new 9x42 table knee mill with dovetail ways does not have this condition if fitted properly.


  1. Jig Boring, A knee mill is not a jig bore but sometimes you can perform this type of machining quite well by tramming the head as close as possible insuring that your bored holes are square to the work piece.

On a bed type mill you can not adjust this squareness, it is built into the machine. It is only as square as the tolerance specified when the machine was built.

If you crash the machine knocking it out of squareness it will have to be scraped in to reobtain the original tolerance.  

CNC Knee Mills made by Elrod Machine using the Centroid Control  can be used in 3 modes.

  1. As a manual machine with a 3 axis DRO
  2. As a 2 axis CNC with the Z axis having  DRO feed back
  3. As a full 3 axis CNC capable of cutting those complex jobs your competitor cuts on his expensive machining center.

In our opinion a knee mill is the perfect choice if you want maximum versatility, if you are needing to take heavy cuts such as making  mold bases etc.

then you might want to consider an Atrump bed mill from us.. If you are wanting to do unattended machining then consider an Atrump bed mill with a tool changer and full enclosure.

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The part pictured here is 30" in Diameter. The part would not fit on the customer's bed mill. Their was not enough Z clearance. So the handy cnc knee mill was employed to cut the detail on the ring. They swiveled the turret and put the table though the ring and fastened it to an angle plate that was bolted to the table.

This Part Was Approx. 32.500" Long.


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