Plunge Router Table Fine Height Adjust

This instructable shows a simple way to raise and lower a plunge router inside a router table.

I found it difficult to set the height in my router table due to the resistance of the spring. When released, the plunge router spring would extend to its maximum, removing any kind of adjustment that had been previously made.

This instructable uses simple materials from a hardware store, and some fairly basic hand/power tools.

NOTE: I have my router table screwed to a piece of wood. The height adjuster may lift your whole router table instead of just the router if you don't have the table screwed to a piece of wood.   I haven't tried it with the table not attached to a piece of wood.

NOTE:  This design may block the vents of your router, or may interfere with speed knobs, etc that are on the bottom of your router.  If you use this design, be sure that you are not going to damage your router by putting pressure on its base, or blocking its air vents.  For prolonged periods of running the router, it would be a good idea to remove the height adjuster.   Additional holes in the pipe flange may also provide adequate ventilation. 

Materials

5/16” carriage (stove) bolt (1) or hex bolt. Other similar sizes may be used if you have them on hand.

5/16” nut (1)

5/16” washers (2)

5/16” knob/handle

1/2” iron pipe coupler (1) from plumbing supply area

1/2” iron pipe flange (1)

Block of wood approx 3” x 3” x 1/2” thick, or a little thicker

Magic marker or other for marking the bolt

Install the router in the router table, and install a tall router bit which you would like to have control over height. Lower the plunge router all the way by releasing its handle, allowing the spring to extend. If necessary, loosen the collet on the router bit and extend it so that its tip is just above the top of the table where it would begin to cut wood. If needed, raise the plunge portion also, and latch it. Measure the distance between the bottom of the router and the workbench, or surface where the router will be used.  This is your minimum height.

 

NOTE: I have my router screwed to a piece of wood. The height adjuster may lift your whole router table instead of just the router if you don't have the table screwed to a piece of wood.

 

Next, push the plunge router all the way in, and latch it. The router bit should be sticking out its maximum from the top of the table.  Measure the distance again from the bottom of the router to the benchtop or piece of wood. This is your maximum height.  The first measurement and the second measurement tell you the length of travel that you want

Now you need to determine how long to cut the carriage bolt.
First drill a hole centered in the piece of wood that is big enough for the bolt to go through.  Next, countersink the piece of wood so that when the bolt sticks through the hole, the head of the bolt doesn't protrude from the block of wood. 
Assemble the bolt, block of wood, and a washer and nut.
Assemble the 1/2" pipe coupler and the pipe flange. 
Assemble the following pieces from bottom to top: Block of wood with bolt, washer, nut, washer, pipe coupling, pipe flange. 
Screw the handle all the way down so that it touches the nut on the bottom, close to the piece of wood.  The bolt should be protruding from the top as shown in the picture. 
Mark the bolt just below the top of the pipe flange.  This is most likely where the bolt will need to be cut off.
The distance from the workbench to the top of the pipe flange is the minimum height that your height adjuster will support.  If the minimum height that you measured is larger, then you are in good shape.  If not, you will have to push your router up a little before you can slide in your finished height adjuster. 
Screw the handle up until the distance from the workbench to the top of the pipe flange matches the maximum height measured on the previous step.  Lift off the pipe coupler/flange assembly and the washer.  Where is the mark on the bolt?  If it is below the level of the washer, then some adjustment will be needed.  Raise the mark so that it is  about 1/2" higher than the top of the handle.  In this case, you will need to raise your router slightly to insert the height adjuster. 
Cut the bolt at the mark, and file/sand the end.  It it is often helpful to put several nuts on the bolt before cutting.  Removing the nuts will clean up the threads at the cut end.

If desired, use silicone or another material to protect the bottom of your router from the metal pipe flange.  It may rub or discolor the router's plastic.  Up to you. 
Reassemble the pieces.
If desired, you can use silicone or JB Weld to keep the washer and pipe thread in proper alignment. 

Extend the plunge router by releasing its latch. 
Put height adjuster to lowest setting where the top of the pipe flange covers the top of the bolt. (Bolt must not stick out of the top)
Slide height adjuster under the bottom of the router.  Depending on your router, you may need to lift the router slightly to slide it in. 
Turn the handle until it touches the bottom of the router, and continue turning to raise the router. 
When the proper height is achieved, lock the latch on the plunge router, and start making some sawdust with your router. 

NOTE: Keep an eye on the temperature of your router.  It may be necessary to remove the height adjust for prolonged periods if it blocks the exhaust port of your router motor