Universal Table Saw & Router Depth Gauge

Why a Different Depth Gauge

Do you have a number of those cheap digital micrometers around the shop. I do in fact I have one in each major station of my shop; table saw, router, main bench, lathe and drill press.

A popular hack is to use these same micrometers as a shop made depth gauge.
This article inspired me to make a version of my own.
I wanted the same gauge to be able to set depth and also to accurately set the fence relative to the cutting blade .... measuring from either side of the blade.

Setting the fence is easy if you have an accurate glide on the fence and you are measuring from the fence side of the blade. However when you need to measure the distance to the fence including the kerf of the blade the process can be less accurate. Sure you can do the math to account for the blade kerf but sometimes the blade is not exactly the width you might think and if you change blades a lot you have to remember what exact kerf goes with what blade. Yes, I am talking about getting close to 1/32 accuracy.

The design

An L shaped frame is fabricated from MDF to firmly hold the mic (micrometer). This design captures the mic at the top of the frame and at the bottom of its sliding arm providing a large depth measuring ability. For me this is the highest position my table saw can achieve.

The L shaped frame is made so that it can lay flat on the table of the saw for accurate fence positioning.

The mic is held in place by a miter miter cut in the frame and by a second holding piece that sandwiches the mic between itself and the frame.

You will have to cut the miter to fit your particular mic as they all have different means of securing the spline (the moving rod) at the end of the slide. Cut the miter depth just short of the thickness of the mic's slide so the holding piece can grip the mic's slide when the wing screw is tightened. Make the miter to shallow to start and the pare away with a chisel until the slide and the holding piece have an interference fit.

The holder is fastened to the first frame by a wing screw (1/4-20 in my case) which is screwed into a pronged Tnut that is inserted into the opposite side of the first frame. The Tnut is countersunk so that the frame will lay flat on the table. I had to grind the wing screw flush with the Tnut so the tool would lay flat.

Frame [3/4 MDF]

Back side

Miter in top right of frame

Measurement

This tool can measure blade height or fence position accurately.

Blade Height Measurement

The height of the blade can be measure easily:

TURN OFF THE SAW!

1. Position the tool on the table with the foot of the frame flat on the table. Make sure your blade insert plate is flush to the table and not biasing the tool.
2. Move the mic's body until the spline touches the table, zero the gauge.
3. Move the gauge to the value that matches the depth * you want the blade to cut. 
4. Position the tool next to and perpendicular to the blade.
5. Move the blade up to touch the spline

*Note: the gauge will read negative values. Ignore the - sign

Fence Position Measurement

Setting and measuring the distance from the blade to the fence is easy;

TURN OFF THE SAW!

1. Lay the tool face up on the surface of the table an perpendicular to the blade
2. Push the foot of the tool up against the fence
3. Move the gauges body until the spline touches the fence
4. Zero the mic.
5. Move the body of the gauge until it reads the distance* you want the fence from the blade, lock the gauges body
6. Move the tool up to and perpendicular to the blade with the spline touching the side of the blade you want to make the cut from.
7. Hold the tool firmly down on the table and move the fence over until it touches the foot of the tools frame [adding a magnet on the back side of the frame may be a good improvement]
8. Lock the fence and check the position again by holding the foot against the fence and observing the position of the spline in reference to the blades teeth.

Zero the mic

Set the desired cut width

Position the spline on either side of blade and move the fence over to touch the foot of the tool.

Enjoy and comment,

Don