Parametric Tubing Drill Jig

I'm working on a project where I need to install fasteners through some aluminium tubing and it so happens this contest has coincided with the project.

All demonstration photos are with ¾ inch aluminium tube, 11/64 drill and M4 bolt, washer and an M4 nut.

This set of drill guides for SAE, metric and 1 inch (25mm), 7/8inch (22mm) and 3/4 inch (19mm) aluminium tubing. I only tested a few different drill sizes, but I seem to get the tolerances right so the code generated for all of the drill sizes should fit. Please let me know if you're having any issues related to tolerances.

These are basically a plastic clamp that's held together with 2x M3 nuts and bolts.

There are two variations of the clamp: with a 6mm-high bump (drill guide) that helps to align the drill, and a version with just a hole of a correct size. The side that's clamped with M3 bolt has always has a drill guide, the side that's clamped with a nut can have either hole or a drill guide.

You can mix and match different drill sizes if you are planning to drill aligned holes of different sizes, as long as they are for the same tube size.

Printing Instructions
 

Print the jig with the clamps towards the bed, the irregularity of clamp arch helps it to fit snug to the conduit.

Notice for the side with nut traps, this object is printed having drill guide and no drill guide version.

Same objects from below displaying overhangs.

Parts & Methods

•  2x M3 10mm bolts (6mm or 8mm should fit too)
•  2x M3 nuts

Insert the nuts into nut traps, the trap tolerances are rather tight so the first time you do it, the nuts should remain in place.

Fasten the jig around a tube.

Drill.

STLs

The following tubes are currently defined

• tube_1 -- a folder with jigs for 1 inch (25mm) tube
• tube_7_8 -- a folder with jigs for 7/8 inch (22mm) tube
• tube_3_4 -- a folder with jigs for 3/4 inch (19mm) tube

File naming:

tube_<tube_size_inches>_drill_bit_<drill_bit_size>_<hex_or_round_countersink>_<guide_or_no_guide_present>.stl 

So a jig for ¾ inch (19mm) tube for 11/64 (4.3mm) drill bit would be called

tube_3_4_drill_bit_11_64_hex_no_guide.stl

For a metric drill bit,  file name would be the following

tube_3_4_drill_bit_4mm_hex_no_guide.stl

Source CAD

Original modeling is done in OpenScad, there's a wrapper Python 3 script that calls scad to generate all of the combinations of different tube and drill sizes.

tube_drill_kit.scad is a file with source definition, you can work with it as-is to generate a single custom drill jig, just modify the following variable at the bottom of the source file.

tube=3/4;
bit_size=11/64;
bit_label="11/64";
f_type="round";
guide=true;
measure="imperial";

Sample metric configuration

tube=1;
bit_size=4;
bit_label="4mm";
f_type="hex";
guide=true;
measure="metric";

For generating updated combination of all tubes and drill bit sizes consult generate_stls.py. It has a set of definition that then repeatedly calls openscad for tube_drill_kit.scad

hardware.scad is my still WIP library for holes for metric fasteners. I used it to create countersink bores for m3 capscrews and nuts that clamp together two lobes of the jig. There be dragons.

I develop the script on a linux system with openscad, python3 and bash. If you are running this on windows, you will need to updated string that gets passed to os.system like so – https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Using_OpenSCAD_in_a_command_line_environment#Constants

To re-generate STLs, place generate_stls.py and tube_drill_kit.scad in the same folder, place hardware.scad in ../libs/ relative to that folder, then run the following command from the original source folder like so

python3 generate_stls.py