3900 Mini Mill SOP



Always wear safety glasses when performing ANY operation on the machine tools. Make sure that long hair is tied up and that any dangling clothing/jewelery is removed. Closed toes shoes are required at all times in the machine tool area. Never use machine tools if you are alone in the lab.

Machine Set-up

Machine component description


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Make sure that your stock is securely fastened in the vise such that you can complete the intended operation without moving the part and without crashing the tooling into the vise.


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A note about tooling

Tooling in the US is almost exclusively in imperial units. This is because it is still cheaper to continue manufacturing tooling in imperial units than to switch to metric.

End Mills

End mills are the work horse of manual milling. They come in a variety of sizes and shapes.
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Drill Bits

Drill bits are just like every other drill bit ever. Please keep machine tool drills separate from other drill bits in the lab.
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Edge finder This tool is used to set the origin of your working surface.

Machining speeds

Choosing an appropriate machining speed is critical for the safe and effective operation of machine tools. There are two criteria that need to be determined before operating the machine they are; spindle speed and feed rate.

Spindle speed: refers to the rotational speed of the tool and is set by use of the dial located near the bottom of the mill control panel.

Feed rate: is the linear speed with which you are going to move the tool across the material. For manual machines this is more ambiguous as it is determined by the speed with which the operator turns the controls of the machine while performing machining operations.

Here is a chart of feed rates and cutting speeds put out by the manufacturer of this machine. feel free to use their built in calculators to figure out the appropriate settings for the machine.

Machine Operation

Once your material is securely fastened in the attached vise, install the desired tool by removing the black plastic cap from the top of the machine to reveal the locking screw. select the appropriate sized collet to hold your tool and insert the tool into your selected collet, tool should fit snugly into the collet without being hard to slide in or out. Place the tool and collet into the tool holder, making sure to align the keyway on the collet with the key inside the tool holder, and tighten the locking screw with your fingers to make sure that it is not cross threaded. ** WARNING:** Tools may be extremely sharp. When inserting the tool into to tool holder grip the tool by the base of the collet to avoid cutting your hand.

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Power on the machine by pressing the green power button located on the left side of the control panel, pictured below. The green power light on the front of the control panel should come on.

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Select the spindle speed from the above chart and set the correct speed using the knob on the control panel. Caution: it is not advisable to exceed 1500 RPM on this machine.

Machining controls

Manual machines are controlled by turning dials which control the X, Y and Z axis movement of the tool. The location and details of these dials are described in detail below.

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The Z-axis can be controled at both fine and coarse incriments. Switch to the fine control by pushing the coarse control handle (pictured above) until the drive teeth have completely engaged. The fine control will now turn smoothly.

Caution: Never move a tool that is not spinning across the work piece. do not stop a tool that is in contact with the work piece unless it is an emergency.

Using an edge finder

Edge finders are a device used to visually find the edge of a piece of material. This allows you to accurately place machined features in the correct locations on the part. Below is a video detailing the use of an edge finder.

Here is a video describing the proper use of an edge finder for locating the position of your material in the vise.


With an appropriate end mill installed in the machine. Move the quill to the desired position at the surface of the part move an additional distance below the surface of the part corresponding to the desired depth of cut and move across the material in the desired direction. Reminder: Take cuts in multiple passes whenever possible. This takes developing a little intuition, just remember that a shallower cut at a slower feed rate will almost always result in a better surface finish and a more dimensionally accurate part.


The manual mill may be used much like a precision drill press. After setting the desired location of the hole usinf the X and Y controls use the doarse Z-axis control to move the quill down into the work piece. Remember to use a proper “pecking” technique to increase tool life and achieve a more dimensionally acurate hole.

Here is a video showing proper drilling technique.

Clean up

Please clean up after yourself! We are not your mother.