Drill Bit Gauge/Sizer - Inch and Metric

It sometimes happens that the home shop has a bunch of loose drill bits that need sorting - this gauge is designed to speed up that job.

In addition to the 3D printed parts, this also requires :

• two aluminum strips; 1/8" X 1/2" X 160mm
• four M3 X 10mm SHCS with washers and nuts

The odd measurements on the aluminum strip are because I purchased a 3ft length of 1/8 X 1/2" aluminum strip from a local big box store (in the USA). 

For a print using metric size aluminum (aluminium?) strip  have also included a drawing for metric size strip . This applies to countries where aluminum strip is commonly sold in 2mm thick X 10mm wide size. This requires that all of the parts be altered slightly to accommodate the slightly smaller strip size . Please note that I have not printed this metric version, so of course I have also not tested it. However, it is essentially the same as the one I printed, so I have high confidence that it will work just as well.

Drawing for both size aluminum strips are included to show hole locations and sizes. Note that the holes in the aluminum strips are slightly oversize to allow for location adjustment.

Assembly, Calibration, and Use

Note: the holes in the two printed parts are filled with a sacrificial fill layer in order to enable printing of the Base without supports, and to improve the print integrity of the Plate. I recommend opening up the holes by piercing them with a razor knife (see photos), and rotating the knife blade to carve out the fill. Do this for both sides of each hole to ensure a clean hole. The instructions below assume you have already done this.

1. Insert the four hex nuts into the holes in the bottom of the Base; push them in as far as possible.
2. Prepare the aluminum strips according to the included drawing (see photos). Note that the holes in the strips are intentionally oversize - this is to allow for some adjustment of the strip position.
3. Place the aluminum strips in the pocket of the base, with the holes in the strips aligned with the holes in the base.
4. Place the Plate onto the base, and insert a screw and washer into each of the two holes on the left (inch) side. Tighten the screws loosely - just enough to holed the strip in place. Adjust the position of the strip on the left (Inch) side so that it is just visible through the V-hole in the Plate, and then tighten the two left side screws to hold the plate securely. Note that there are slots in the bottom of the plate - this is so that a small screwdriver can be used from below to adjust the strip position.
5. Insert a screw and washer into each of the two right side (mm) holes, and tighten the screws loosely as before - just enough so that the strip is held but still moveable. 
6. Calibration #1 : Using a screwdriver from below, push the right side strip top position as far to left as it will go. Insert a 1/16" or 1.5mm drill bit into the V slot, and slide the bit upward until the center of the position corresponds to the bit size, moving the top of the strip as necessary to get the bit to fit. Tighten the top right screw firmly but not tightly (yet).
7. Calibration #2 : Insert a 1/2" or 12.5mm drill but into the bottom the V slot, and using a screwdriver from below move the bottom of the right hand strip as far to the left as it will go. The slide the bit upward until the center of the bit corresponds to the bit size, moving the bottom of the strip as necessary to get the bit to fit. Tighten the bottom right screw firmly but not tightly (yet).
8. How to use (and calibration check) : Check the calibration with various size drill bits by inserting each bit into the V slot and sliding the bit upward until it stops; the mark next to the stopping point is the bit size.
9. Assuming that the calibration check in Step 8 is OK, tighten all four screws tightly (but do not over-tighten!). 

I tested the gauge with various sizes of inch and metric drill bits, and found that with a little practice I could readily determine drill sizes to within 1/64" or 0.5mm. However, I should note that while I could sort inch drills, and I could sort metric drills, I would not rely on the gauge for distinguishing between inch and metric drills which are close in size. In fact, I would not rely on the gauge as the final judge of size in any case, but I think it is a good tool for preliminary sorting.

Print Instructions

Print in PETG using the 3mf files provided (I used a textured PEI plate); otherwise :

Base :

• 0.2mm layer height
• 2 perimeters
• 10% rectilinear infill

Plate :

Note : Allow the plate to cool thoroughly before removing from the printer to prevent it from developing a bend from peeling off the plate.

• 0.2mm layer height
• 2 perimeters
• 0% infill
• print in two color via filament switching

CAD

The OnShape 3D CAD files for this are here :

Redesigned and extended to accommodate drill bits, with appropriate index marks.