Shop-made Small Router Plane

For several years now, if I needed to route a dado or groove that was less then 1/4" wide, I used a makeshift router plane.  This was nothing more than a block of wood with a 45-ish degree angle on the front end, a 1/8" groove cut into that angled front, and a 1/8" chisel clamped into the groove.

My original small "router plane"

The clamp block holding the chisel in place is a piece of wood screwed to the main block

While this worked well during the infrequent times that I needed it, I always thought it would be nice to have a dedicated tool.  So recently I did something about it.

For the blade, I used an old 5/32" Allen wrench.  The 5/32" dimension is flat to flat, and the dimension from apex to opposite apex is close to 3/16".  The short leg of an Allen wrench has one flat face facing up when standing like an "L", so the 3/16" dimension is horizontal, and that becomes the width of the cutting edge after some filing, grinding and sharpening.

The Allen wrench in cross section

I heated the 90 degree bend to red hot and bent it to more like a 100 degree angle.  This gives a "clearance angle"; it allows the blade to cut a dado without the heel of the blade rubbing on the bottom of the dado.

This shows the approx. 100 deg angle on the Allen wrench

One major concern was about how to hold the blade.  I got a 1/4-20 bolt and tried to drill a hole through it.  Nothing doing!  That bolt must have been some sort of specialty bolt, as it was as hard as kryptonite.  I annealed it and it was still way too hard to drill.  So I got another bolt and that one was far easier to drill, though I found out the 1/4" bolt was too small for a 3/16" hole and I had to go with a 5/16-18 bolt instead.

Punching a center point into the insanely hard bolt

Successful 3/16" hole in a 5/16-18 bolt

Here's how it'll work: Allen key through the hole in the bolt, 
nut at rear of the wood block tightens the Allen key to the wood body

I grabbed a chunk of scrap from the bin that just happened to have a 1 1/8" hole bored through it.  About 2/3rds the way up from the bottom of the block, I drilled a 5/16" hole through the back and into the larger hole of the block.  The 5/16" bolt was inserted and a washer and nut placed on the back end.

Also made a groove where the cutter will rest as a sort of "bed"

Made two thumb holes in the back end for a better grip

Then made a large bevel on the top surface (as seen from the right end)

The plane's body is 4" wide, 1 1/8" tall and just over 2 1/8" front-to-back.

Shaping and sharpening the iron was not too tough, but it was tedious.  I filed or ground a flat on the bottom, then filed a bevel on the top.  The diamond plates were used to refine the surfaces and get a nice edge.

Dragging the bottom flat backward on the diamond plate

And sharpening the bevel.  This took a lot of patience.

But I got a good smooth surface on the bevel ...

... and the bottom flat

I finally got a wingnut to tighten the iron in the body - a nice upgrade from a hex nut and wrench to tighten.  A nice project - I'm looking forward to using it when the need arises.

In use cutting a ~3/16" dado

Glamour shot

Back view showing wingnut

And lastly, I made two more smaller irons - one about 7/64" wide and one about 5/64" wide.  It was a challenge sharpening these tiny irons, but they all came out great and work well.

Three small Allen keys became router plane blades

All for now.  Hopefully I'll get back in the flow soon and post more often.  I've been in a woodworking slump for the last couple of months.