Airfield Models - How To

Make a Split Fence for a Router Table

March 20, 2009



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Airfield Models (http://www.airfieldmodels.com)Make a Split Fence for a Router/Shaper Table

The fence is the heart of the router table.  I built my first table with no knowledge of how they're supposed to work and I subsequently used my table saw fence instead of making a proper router table fence.  I didn't know any better.

The table saw fence worked well for some things but it failed miserably when trying to route edges because the bit was in front of the fence instead of behind it where it's supposed to be.  I decided to build a new table and fence from scratch.

I've been looking at various router table designs and fences for several years with the intent of picking out the features I like most and incorporating those I would be most capable of producing accurately in my shop.  Accuracy is very important because each item in a system introduces its own inaccuracies.  The sum of these end up in your work.

For most purposes a single fence with an opening in the middle to pass bits does everything we need it to.  The only time I can think we would want a split fence is if we're performing a router operation that removes the entire edge of the material passed through it such that the out-feed fence needs to be adjusted farther out than the in-feed fence.

I doubt I'll use the split feature of this fence too much in my work but for those times when I need it I'll have it.  The bulk of the work I do with a router table will use the fence as a single fence instead of a split fence.  In other words both fences will be aligned in the same plane.

I built this fence and the table it goes on with the intention of it being the last Dremel router table I'll ever need so everything is designed and finished to last more than a lifetime.

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Making the Fence

My Fence is made from red oak and aircraft plywood.

I laminated three layers of 1/16" aircraft plywood together to make a 3/16" thick base and fences.  The center lamination is cross-grain to the outer laminations whose grains run parallel to the longest dimension.

This project requires a fair amount of precision for everything to line up properly.  My machinist's square was the most valuable player.

I cut out the base but didn't drill any holes in it until all the other parts were fabricated.  There are two adjustment rods for each fence half that are a close tolerance to their mating holes.  They need to align very well.

I assembled the rods, fence supports and rod clamping blocks as a unit and then attached them to the base with permanent double stick tape.

When the parts were in place I clamped them for a couple minutes to establish a good bond with the tape.  Then I checked that everything worked properly.  When I was satisfied with the operation I drilled one hole at a time through the base into the blocks and threaded in the screw.

When all the holes were drilled I removed the screws, popped the fence assembly off the base and cleaned off the tape.

All parts are numbered so they don't get mixed up.  The fences and fence supports are also numbered so I know which end is which.

The two fence supports are machined from 3/4" square red oak.  This is the back of a fence support.

I chamfered the ends of all the blocks.  Normally I round things over.  I wanted to do something different.

The chamfers are fairly large and give the fence a more rugged look.

The front face of the fence support must be sanded dead flat perpendicular.  If it isn't then the fence will not be flat either which will make it difficult to use the system accurately.

It might be worth it to pay a wood shop to joint the fence supports and save you a lot of work.

If the rod supports aren't perpendicular to the face in all respects and absolutely parallel to each other then you can bet the fences won't move smoothly and if they're off by too much the fences might not move at all!

Sand the faces flat before you drill for the adjustment rods.  Drill for the rods with fence supports face down on the drill press table.

Four clamp blocks are cut from red oak.  A 1/4" hole was drilled then reamed with a 1/4" reamer to allow the fence adjustment rods to slide through easily.  I used my Fox propeller reamer which worked well.

A hole was drilled top to bottom and tapped 8-32.  The hole above the cut is drilled two sizes larger to allow it to slide over the screw when the wing nut is tightened.

After the clamp rod and clamping screw holes were drilled an opening was cut that allows the block to clamp the rods.

This clamp does not need to be tight.  It only needs to be tight enough to remove play.  It's ok if the rods can slide.

The springs and indexing bolts hold the fence in place.

The bottom of the block is countersunk to bring the 8-32 flat screw head flush.  Again, all parts are numbered because I made them accurately enough that they are interchangeable in regard to mounting them but they aren't accurate enough to prevent binding if they get mixed up.
1/4" music wire is used to make the fence adjustment rods.  I cut the rods to length.  I put each one in my drill press and used a Dremel with an emery bit to cut groove about 1/32" from the end.  A 7/32" E-clip snaps into the groove to retain the return spring.
This wasn't as difficult to do as I imagined it would be.  It took less than ten minutes to cut grooves in all four rods.
The 3/16" aircraft plywood fences are attached by four #4 x 1/2" flat head brass wood screws.  The fences close to a 1/2" gap and open to a maximum of 1-3/4".
The mounting holes are countersunk on the front side of the fence such that the screws heads are slightly below flush.  The edges of the holes were sanded to ensure that nothing protrudes that could catch work being moved across the router table.
The inside edges of both fences are beveled to 45.
Four fence adjustment blocks are cut from 3/4" square oak.  A 1/2" forstner bit was used to drill to 3/16" from the back of each block.  The back was then tapped for an 8-32 bolt.  It would be better if I'd left more material for the 8-32 bolt.

I chose a screw size having thirty-two threads per inch so that adjustments don't require complex calculations.

one complete turn of the screw equals 1/32" movement.  A half-turn = 1/64" and a quarter-turn = 1/128".

Each fence can adjust about 3/8" which is way more adjustment than I can imagine being necessary in any real-world use.

The front of a fence adjustment block.

The base is 3/16" x 2" x 20" aircraft ply.  Mine is made from three laminations of 1/16" aircraft plywood.

Each block  is attached by four #4 x 1/2" flat head brass wood screws.  Two slots are cut in the base to allow for coarse adjustment of the entire fence system.

I use knobs having a 10-24 stud to mount the fence to the router table.

Long handle knobs will work much better than what I chose.

All holes are countersunk on the underside of the base to bring the head of the screws below flush so they don't rub against the table.
All the hardware to assemble the fence and attach it to a table.  The only hardware missing are the blind nuts that are embedded in the underside of the table.

The six screws to the left of the four black knobs aren't part of the fence system.  They are used to mount the router insert into the table.

The adjustment rods are a press-fit into the fence support blocks.  After the finish was applied and rubbed out the rods were hammered in using a rubber mallet.

If the rods were loose then I would use a couple set screws to retain each rod.  These are so tight that I don't have any worries about them loosening over time.  If for some reason they do loosen in the future I'll either epoxy them in place or drill and tap for set screws.

Ensure the fences are perpendicular to the table.  If you were careful then they should be very close.  if they aren't then use a punch to knock the rods slightly back from the face of the fence support blocks and then sand the blocks until they are perpendicular.  When you're satisfied hammer the rods back in.

After the clamp blocks are attached, slide a return spring over the adjustment rod and then snap an E-clip in place to retain it.

Ace Hardware has a huge assortment of springs.

I bought two different sizes because I didn't know how much force would be necessary.  The sizes I purchased were numbers 147 and 149.  I don't know the number of the spring I ended up using but they're both the same size with one being made from a larger diameter wire which is what I ended up using.  The lighter spring didn't return reliably.

Bolt on the adjustment block.

The knob at the rear adjusts the fence out when the screw is turned in.  When the screw is turned out the spring pulls the fence back.

I've found that vibration from the Dremel running don't cause the knobs to turn and lose their settings.  If the knobs do turn on their own then I'll have to use the clamps.  To adjust a fence the knob will be turned until it makes contact with the rod before the clamp is loosened.

Clamp the assembled system to the table.  Adjust both fences so they are as far to the rear as possible.  Now adjust one fence forward by turning both adjustment screws two full turns in.  This will space the fence 1/16" forward of its rear-most position.

Use a good straight-edge and align the other fence so that it is in the same plane as the first fence.

Sand the edge of a piece of scrap wood until it is straight.  Slide it along the fence in both directions and ensure it doesn't catch either fence.  Adjust the fence as necessary.

Now scribe a fine centerline on top of all four knobs.  These will be the indexing lines.

Another view of the completed fence.

The base and fences are finished with several brushed coats of clear polyurethane that was sanded between coats.  The last coat was rubbed with #0000 steel wool.  They were then given a good coat of furniture wax and buffed.

The oak pieces are finished with Danish oil.  After the oil dried I applied a couple coats of clear polyurethane to further seal the end grain of all the oak pieces.  All these parts were also rubbed with fine steel wool.

All you need is a good router table to mount the fence.

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How To Make a Router/Shaper Table for use with Dremel Moto Tools
How to Make a Wire Splicing Jig

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Copyright 2007 Paul K. Johnson