The Joys of 3D Printing Jigs

 

Jigs are absolutely essential in a lot of things that I build. They allow for repeatability, and generally makes my life considerably easier when fabricating anything. With CAD and 3D printing becoming mainstream, the jig making process has become even easier and precise. Not only can 3D printers print out models, they can be used for functional, dimensionally accurate prints too. To demonstrate the versatility and ease of 3D printed jigs, I will be going over three examples of jigs I made and how printing them was the better option.

Drill Guide

Before I had a drill press, I had to find some way to drill perpendicular holes in things with a handheld drill. Ordinarily in materials like wood, that accuracy wasn't super important, but it becomes super important when working in metal with multiple bolt holes that had to line up. My first thought was to drill a straight thru hole in a block of wood and use that to support and line up the shaft, but making sure that was straight first was hard to test, and it blocked sight lines to the actual piece. Enter the 3D printed bit guide. 

Drill jig CAD

This was designed specifically for the job at hand, which was drilling holes for 10-32 screws on a 3/4" angle iron. Thus, the jig is exactly 3/4" wide and 1-1/2" long, and consists of two holes, one sized for tap holes and the other for clearance holes. Lines were scored to the edge to signify where the centers are, which helps in placement when the drill point is obscured. And since it was made in CAD, the holes are exactly perpendicular to the surface. This afforded me both precision, as well as much more detail than I would have gotten from a handmade jig. It didn't last very long due to heat, but it got the job done for the few holes I needed to drill. A future iteration would have a thicker base for extra thermal capacity and strength, but I have a drill press now, which replaces the need for this jig.

Bolt Pattern Finder

This example focuses on another aspect of the jig, which is for measurement and repeatability. I needed to match the bolt pattern on a wheel hub to a chain sprocket, but I did not have the physical hub for me to compare to. Thus, I could only work with the schematics for the bolt pattern. It also had to be repeatable, as I had two sprockets for two wheels. I did have the sprockets, which let me measure and build a jig off of it.

Completed jig

Jig in use

The jig consisted of two parts - one main frame which clamped onto the sprocket, and five inserts where the holes would be. I decided to print the inserts separately because I was unsure how large the hole would need to be to let the punch leave a mark, and it was faster to print five new inserts than a whole new jig. Plus, if the punch cracked the insert, I could simply replace it with a new one. The main frame is centered exactly on the sprocket, with a lip going inside the sprocket hole, and nubs holding it against the arms of the sprocket. This ensured that the diameter of the holes were exactly the same, and each hole was exactly centered on each arm. Instead of painstakingly marking up and measuring the position of each hole on each sprocket, I just had to CAD it once and print it out. This was a huge time saver, and removed any possibilities of human error in measurement.

Perfectly concentric and dimensionally accurate pattern

PVC Pipe Jig

This jig was used to let me drill centered holes on two sides of a PVC pipe. This was quite challenging for me to figure out, as the holes had to be centered in the pipe, which while it's easy for one side, was difficult to do on the perpendicular side. In addition, I didn't have a pipe jig for the drill press, so I was stuck to my regular drill vise, which could deform the pipe as I tightened it. This is where the jig came in handy.

Final pipe jig CAD

This jig was pretty simple. It simply consisted of an octagon, with a hole inside perfectly matching the diameter of 1/2" Schedule 40 PVC. Two or more of these would then be used on the pipe to bridge the gap. On all sides, there is a cut to indicate the center line. The way it works is that you first draw a straight line on the pipe, which is simple to do. You then line up one of the center marks on the jig to that line, and clamp it down. The flat surface presents an orientation of the pipe, and to get a perpendicular hole, it can simply be rotated 90 degrees and clamped back down. The jig itself gets clamped instead of the pipe, reducing the squeezing pressure on it, and keeping the surface from getting marred. It's a very simple design, yet is extremely versatile on the drill press. The octagon shape also allows it to be placed at a 45 degree angle as well, but I did it mostly to conserve plastic and have a slightly more svelte design.

Jig in use, with many holes drilled

Conclusion

As these simple jigs have shown, 3D printing has made the jig making process far easier and more accurate. None of the jigs were particularly difficult to CAD up, with each taking less than ten minutes to make, yet they are far more precise than any jig I can fashion out of wood or scrap material. Now there are limitations - strength is pretty dependent on the plastic it's printed in, and proper dimensions require a properly calibrated printer, but I believe these can be factored in through design, and make for better parts and prints outside these jigs. The utility of 3D printing in the manufacturing process is looking bright.