Woodbutchery, part two

The other small project I'd intended to get done today was to make some zero-clearance inserts for my table saw. Most table saws are sold with a general-purpose insert that works reasonably well for most purposes:

The one on the left is the original that came with my saw. The one on the right is my first home-made insert. As you can see, the slot for the saw blade is much larger on the original than it is on mine. The advantage of the home-made model is that if you're cutting very small parts, there's little or no chance that a small cut-off will fall down through the slot and into the saw body. It also provides better support for the cut edge, which reduces splintering and tear-out of the wood fibres.

It was easier to make the new insert than I'd expected, but having the right tools made a difference. I started out with a sheet of 1/2" MDF, and cut out some blanks:

The orange object on top is the original dado-blade insert (note the wider slot in the top). It had a flatter surface, which made it the obvious choice to use as a template for the blanks. I attached the first blank with some double-sided carpet tape and then used a bearing-guided straight bit on the router table to duplicate the shape of the original insert:

The bearing on the top of the bit runs against the edge of the original, while the cutting edges are trimming off the excess material on the blank. The black hose is attached to my shop vacuum: MDF dust isn't something you want to be breathing a lot of.

My mistake on this project (there's always at least one of 'em) was to use the dado insert as my template: it's slightly shorter than the regular insert and there's a small rubber spacer at the back to snug it up to the front of the throat: all of my blanks were slightly too short as a result. Here's how I tried to fix the problem:

That's a small grubscrew at the back of the insert. To adjust it to the correct length, use an Allen key to shorten or lengthen the exposed screw. It worked, thank goodness. The original inserts are slightly thicker than the MDF blanks I used, so I had to drill out some adjustment holes for more grubscrews so that the new inserts could be level with the top of the table:

I may need to find some longer grubscrews: these are at about their limit without losing their grip in the MDF. An alternative fix might be to laminate some thin material underneath the drilled holes (about 1/16th of an inch would be about right) to provide a bit more depth.

The day's output (it was easier to mass-produce them once I'd got the first one working properly):

The one at the far right is used with a regular-width blade. The rest will be used with the dado stack at various widths (I didn't feel up to messing around with the dado blades today, so that will be a job for tomorrow).