Jigs: What I’ve Learnt So Far

Someone recently shared how they felt jigs were overwhelming but felt inspired to make a few after seeing some of mine.

So, i thought of sharing a few insights on making jigs from my own experience. I don't have any formal training - i learned by observing and practising. I often use my own simpler lingo to explain especially when I have had students.

What are jigs?

Say you want to draw a straight line with a pencil. You could do it freehand - if you are skilled enough. Most of us, from early days, have used a ruler.

Keep the pencil against the ruler and you get a straight line, every time.

That ruler is a jig! A jigs is made for a specific purpose.

In woodworking, all our tools remove portions of wood away from wood through cutting/sawing, filing/sanding, etc. because wood is a subtractive material. And all the tools also have some inherent purposes. You can't sand with a saw - that's meant for cutting - it is in its design.

Jigs let us control those tools in ways that make spcific jobs easier, repeatable or even possible. As such, jigs unlock different purposes. I classify them in the two categories:

1. Repeatable jobs: think of cutting a specific length 50 times. Instead of measuring each time, the simplest jig would be to cut a piece of wood to length and using that to mark each piece.

2. Unlocking capabilities: A handplane can flatten a surface, but using it free hand doesn't guarantee a particular thickness. You could easily end up with 20 mm on one side and 17 mm on the other. A thicknessing jig constrains the plane so it can remove material only upto a pre-determined depth.

To understand more about the concept of jigs, let's first decode a few of them.

1. Magnetic Saw Guide

Goal: Crosscut a plank accurately at 90° or 45° using a hand saw.

Problem: My blade doesn't always remain straight, it can wander - producing a cut that isn't straight or square.

The purpose: Keep the blade straight by constraining its movement.

How does the jig work?

• First there is a straight edge on 1 side and a 45 on another. This alone if used as a fence improves cut accuracy.

• A stop block towards the end of this piece removes the need to clamp it each time for 90 or 45 cuts.

• Magnets along the edges hold the blade so it reduces swaying of the blade left-right or curving clock/anticlockwise.

2. Thicknessing Jig

Goal: Reduce pieces of varying thickness to exactly 5 mm (or any other preferred thickness) using a hand plane.

Problem: Planing freehand requires repeatedly checking thickness along the entire piece.

The purpose: Get 5 mm efficiently with less time by limiting how far the plane can cut.

How does the jig work?

• The hand plane runs back and forth along two rails while the workpiece sits underneath. The top surface of the wood gets removed. The distance between the rail and the base determines the final thickness.

• To accommodate for different thicknesses of our stock, the bottom base of the jig can lower or come up in parallel with reference to the rail. How?

• The base wood has threaded inserts and the rail has slots for the bolts that go into the threaded inserts. By loosening, height can be adjusted, and locked at the right depth.

• Now each time I will get the same depth without error.

Did you notice a common thread about these jigs: references!

References are pre-requisites in wood i.e. how the wood should be for this jig to work. It could be a surface, edge, angle or dimension that the jig relies on to work correctly.

Think back to the ruler. It works as long as it is on a flat surface - a sheet of paper. You can't use a rule to mark a straight line on the surface of a tube. The pre-requisite (or the reference) for ruler is a flat surface.

The same principle applies to woodworking jigs.

Magnetic Saw Guide: The surfaces of the workpiece that contact the underside of the guide need to be flat and square to each other. The jig's 90° reference depends on this.

Thicknessing Jig: The plane blade is 50 mm wide, while the plane body is about 66 mm wide. The rails therefore need to leave clearance for the blade so it doesn't contact them. This means the jig can accommodate stock up to 50 mm wide, but not wider. The two rails also need to remain parallel and at the same height. Otherwise, the jig will introduce a taper. The stock's height and length, however, are less restrictive. The rails can simply be made tall and long enough to accommodate the workpieces you intend to use.

Understanding these references is, in my opinion, the key to designing good jigs.

What to keep in mind while designing jigs?

1. Clear Purpose: What exactly do I want to achieve? What are the dimensions, angles or shapes involved?

2. Method: Am I cutting, removing material, shaping an edge, drilling, or doing something else?

3. Tool: Which tool performs that operation? What are its inherent constraints and references? For example: Hand plane blade is 50 mm wide.

4. Starting Step: What is the simplest jig that can achieve the job accurately?

   Start there. Complexity can come later.

A few things I've learnt

1. Do research on Youtube: For most home projects, there is a plethora of content available on youtube.

2. If you don't have experience of making jigs then pick simpler designs because there is a high chance of errors during the making. Over time you get the confidence for more complex jigs.

3. Think long-term: Can you make a jig that will unlock more possibilities than your current project? Maybe the answer is in making something adjustable?

4. Go slow, and take the process as a learning. if mistakes happen, don't feel discouraged, try to diagnose the mistakes and rectify or begin again.

5. Jigs require upkeep. Most are made from wood and wood expands/contracts. Check your jig with a test piece before important work.

6. Overbuild where safety matters. Screws, bolts, clamps and locks are cheap compared to a tool flying out of a jig. If something is holding a moving tool, make it secure.