Thread: Setting an Incra mitre gauge square

I had to take the gauge apart again for another reason. I found that the face of the fence was not square to the table. The problem was that Incra put a very thin layer of some sort of tacky substance underneath the L-section that connects the fence to the protractor part of the gauge. I've no idea why they do that but I just scraped it off and cleaned up the L-section and protractor.

While I had the L-section off, I observed there were substantial burs around the threaded holes on the protractor. My guess is that the holes were drilled with a single drill bit direct to size. The burs were causing unnecessary friction. I filed off the burs.

After those tune-ups, the fence face was almost perfectly square. I gave the L-section a touch up with a file on the face that the fence rides on to make it perfect.

I must have got lucky the first time I added the adjustment mechanism. I now had considerable trouble.

The problem is (in my opinion) is that there is no defined pivot point. The three holes on the L-section are a 1/4" diameter and the screws are quite a bit smaller. I didn't measure them but probably 3/16". This difference between the hole on the L-section and the socket screw thread diameter is how Incra allow the adjustment to take place. Pretty ordinary design but it does the job. Kinda.

To create a pivot point; I drilled out the central hole to 1/4" and used a 6mm spring pin as the axis to pivot on. A 1/4" steel dowel would be better, but I didn't have one. Spring pins are always slightly oversize so it fit perfectly with gentle taps with a hammer to get it inserted. It's not a high wear situation and it will probably last the life of the tool.

Adjustment is now super easy and highly predictable.

Considering the price of Incra mitre gauges, the design of this critical adjustment is pretty damn average. Luckily it's easily fixable; but for the price, you shouldn't have to.