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Depth Gauge2

This particular depth gauge is one that I designed and developed over 20 years ago and it is still my favorite after all this time. It is comfortable to hold and robust enough to be able to take a reasonable cut. The body being made from a hard wood just glides over the clay surface without digging in.

 

So with that brief introduction, let's proceed in making the tool.

 

 

As you can see from the photograph on the left, we have the basic materials to start the project.

 

This consists of a block of hardwood i.e. beech, oak, maple etc. 2 3/4"x 2"x 5/8"

 

The blade is made from steel flat stock.

5"x 1/2"x 1/8"

 

Hardware: 

 

1/4"-20 Wing nut

1/4"-20 x 3/4" Hex Cap Screw

1/4" Locking Washer

        

The illustration on the right shows the dimensions for marking out the hardwood block.

 

Start off by marking the slot to accept the blade. This can be cut to the line on a bandsaw or with a handsaw, then chisel out the material to a depth of 1/8". Check the slot width with the steel flat stock, it should run smoothly up and down the slot. Also check the depth of the slot against the steel, it should be flush.

 

Mark the position of the hole that will house the bolt, 7/8" above the base and center of the slot. Using a 1/4" drill bit, drill the hole. Flip the block of wood over and counterbore the 1/4" drilled hole to a depth of 5/16" with a 3/8" Forstner bit. This will give a flush condition when the bolt is put in place with a locking washer to secure the blade.

 

At the top of the block, mark in 3/8" either side and scribe a line to the corner of the base giving a trapezoid form. Cut off excess material with a handsaw or bandsaw and sand smooth.

 

At the bottom of the slot where the cutting face sits, notch-out to a height of 3/8". This will prevent clay from clogging the cutting edge when shallow cuts are made.

 

This completes the wooden base of the depth gauge.

 

 

With the 5"x 1/2"x 1/8" steel flat stock, mark-out the slot by scribing 1/8" parallel to the edge of both sides giving you a 1/4" wide slot. From the end measure 3/4" and scribe a line then measure 3 3/4" and scribe a line. This gives the overall length of the slot (3")

 

Mark-out the cutting edge by scribing lines 1/16" across the bottom edge and parallel on both sides to a height of 3/8". This gives you a square box of material that will be drilled out then filed to the scribe lines to produce the cutting faces.

Now that the steel has been marked out, set-up the drill press with a 1/4" drill bit. Clamp the steel in the drill press vise, this will secure the metal and prevent any accidents should the drill suddenly grab the metal. It will also provides control for the drilling operation.

 

Start by drilling the ends of the slot first, this way you'll know the exact start and finish and proceed by drilling holes as close together as you can without wandering into the adjacent hole. Once this is done drill out the excess material in the end box, this provides the start for the cutting faces.

 

With all the drilling complete, the slot can be finalized by filing through the drill holes to obtain smooth sides ( see blade in above photograph)

The drilled hole in the end box needs to be filed until you meet the scribe lines to produce a square box. Once this is done, use a Swiss file to sharpen the blade to a chisel like edge, this should be done on the bottom edge and the two side faces of the blade on both sides. This will give you a triangular section as in the sketch above.

 

Before finally assembling the parts, the body can be sealed with boiled linseed oil. Once it has dried use a paste wax and buff smooth. The blade can also be de-burred, the only sharp area should be the cutting faces.

 

With the body and blade complete, it can now be assembled. Place the 1/4" locking washer over the 1/4"-20 x 3/4" hex cap screw and insert through the back of the body. Then place the blade over the cap screw and secure with the 1/4"-20 wing nut.

 

Check the performance by sliding the blade up and down, it should run smoothly with minimal side play. The blade when fully retracted should lie flush with the bottom of the body. When the wing nut is tightened the blade should be held firm.

 

If all these conditions are met then the depth gauge is ready to go....

 

Down load the custom depth gauge illustration to build this tool.   Custom Depth Gauge PDF

 

Copyright © 2004 - 16 Steven Austin

                                                                                                                      

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