What is a Doweling Jig?

What is a Doweling Jig

We know dowels and dowel joinery.  We’ve written about it in the past and distinguished it from biscuit joinery in an earlier piece which you will find here.

Dowel joinery involves drilling holes in the two pieces being joined together, inserting dowels, and gluing them into the aligned holes in each piece.  Dowel joinery makes a very strong bond that is clamped and allowed to dry and cure.  Some argue the bond is stronger than mortise and tenon joinery, even.

While biscuit joinery might be acceptable when crafting a table top of multiple boards, the use of dowels will provide a stronger bonding.  The extra gluing surface of the dowels penetrating deeply into each piece being joined provides a strength well beyond mere gluing and is stronger than biscuits. 

As with biscuits, the alignment of the holes in each piece is crucial.  So is the depth of the holes being drilled.  The size of the dowel, both in diameter and in length, will be determined by the dimensions of the boards being joined.

What Woods Are Dowels Usually Made From?

WEN JN400D 400-Piece Fluted Dowel Pin Variety Bucket with 1/4, 5/16, and 3/8-inch Woodworking Dowels

Dowels are cylindrical rods usually made from wood, although there are plastic and metal dowel rods, also.  For our purposes, we’ll focus on wooden dowels.  When they are cut into short lengths, they are referred to as dowel pins.

Dowel pins are most often made from hardwoods, like beech, poplar, and mahogany, as well as ash, oak, and cherry.  Oak is considered to be the strongest of wooden dowel rods and pins.  Sometimes, too, a softwood like pine will be used. 

If you need a refresher on hardwoods and softwoods, you can look at a previous piece we wrote on the subjects here.  Not all hardwoods are hard, and sometimes softwoods will be hard woods – pine, for example.

Is There a Standard Size For Dowel Pins?

Dowel pins come in a variety of sizes ranging from 1/4”, 5/16”, 3/8”, 7/16”, and up to 1/2”.  Most of the time, they will be 2” in length.  However, if you purchase a dowel rod and cut your own pins, you can choose the length yourself.  Oftentimes, dowel pins are sold in bags of 50 in an assortment of those sizes.

As a general rule, the size of the dowel should be no more than half the thickness of the stock being joined.  So, if you are joining two 1” boards, the dowel pin should be no more than 1/2“.

With the preliminaries out of the way, let’s get to the doweling jig itself.  What is it?  What does it do?  Why should you use one?

How Does A Dowel Jig Work?

AUTOTOOLHOME Self Centering Doweling Jig Step Drill Guide Bushings Set Wood Dowel Jig Woodworking Joints Tools

A doweling jig is a purpose-made (made for a specific purpose) tool that takes the worry out of drilling the holes into which the dowels will be inserted in joinery.  The jig acts as a drill guide and removes that worry in two ways:

  1. The jig has metal bushings or sleeves that your drill bit is fit into to guide the drilling; and,
  2. Those bushings hold the drill bit in proper alignment on the item both to its center and square to the edge.  That self-centering is a strength of a dowel jig and relates to our earlier mention of the relationship between dowel size and workpiece thickness.

In other words, it performs the same task and provides the same benefits as does a biscuit joiner and a Festool Domino in biscuit and domino joinery.  The hole will be drilled in the right place of the workpiece, and you set the drill depth based upon the length of the dowel you will be using. 

The block, whether steel or plastic, of the jig has bushings or sleeves that will guide your drill bit.  The bushings are in the exact center of the block, meaning the hole you drill will be in the exact center of the workpiece.

A screw or screws run through the block, and when turned, move both sides of the jig in unison and in equal amounts as it clamps onto the wood.  This is how the self-centering is achieved – the block is not pulled in either direction but remains centered on the workpiece.

Jigs will have a window, also, that allows you to see into the alignment.  The importance of this will become apparent in this walkthrough of how to make a dowel joint:

  • First, choose the right dowel size and appropriate drill bit for the workpieces. Then measure and mark the locations of the dowels with your handy carpenter’s pencil.
  • Match the pencil lines with the lines on your dowel jig through the window(s), and clamp the block to the workpiece. Drill the holes.
  • Glue up the dowels and holes, and insert the dowels into the holes. Clamp the pieces, allow the glue to dry and cure, and you have your dowel joint.

To illustrate the process, here’s a video we found for you that demonstrates the use of a dowel jig in a couple of types of dowel joinery.

Do You Need a Dowel Jig?

Woodworkers are pretty creative and inventive in their craft and invariably will come up with tool workarounds – – how to do what the tool does but without the tool.  The short answer to this question is no; you don’t need a dowel jig.

They are convenient to have, and some models are not particularly expensive, as you can find a plastic jig for under $10 if you are a frugal shopper.  Some, though, with steel blocks, can run $75 and up.

Here’s a video showing how you can use nails to mark your workpieces for an aligned dowel placement on your workpieces.  It’s pretty simple and can help you create a decent and strong dowel joint.  We might suggest you show a bit more care in centering the holes for dowel placement than he did, but the video does demonstrate a workaround that can accomplish the same thing a jig could.

There are also what are called dowel centers, small metal fittings that serve the same purpose as the nails did in that video. 

Holes are drilled in one of the workpieces, and the centers are inserted into the holes; a small spike protrudes out of the top of the fitting.  The workpiece is then placed on the second workpiece to be joined, and with a little mallet tap, the spikes will mark the spot on the second workpiece where the holes should be drilled.

These dowel centers come in packs of various sizes to match the size of the dowels you’ve chosen for your project.  You can find them both online and in hardware stores and the large DIY stores for under $10.

Here’s a video that shows the use of dowel centers.

You might ask yourself why you would spend $10 for dowel centers rather than spend $10 on a plastic dowel jig.  That’s a good question.  For the occasional dowel joint you might need to make on a project; a plastic dowel jig will serve you well.  It doesn’t have the self-centering talent of a more expensive jig with a metal block, but if you measure well and align the jig carefully, you will be fine.

But, as the dowel center video demonstrated, there are some dowel joints for which a jig is not well suited.  In those instances, a $10 bag of assorted size centers will do the job for you.

Can You Make Your Own Dowel Jig?

Again, if you can think it, and it can be made out of wood, then, of course, you can make your own dowel jig.

What does a jig need to be effective?  It needs holes (you can drill them yourself); it requires a “window” to be able to see into the workpiece for proper alignment (you can drill it yourself); it needs bushings to help align the drill bit (you can insert them yourself into the holes you drilled).  So, if you measure carefully and can drill holes, you can make your own dowel jig.

Don’t believe us?  See for yourself in this video of an inventive creation of a dowel jig with a couple pieces of wood, a drill, two bushings, and a clamp.

If not now, eventually, you will begin a project that will require joinery, and dowel joinery is a very good choice for its strength and endurance.  Having a dowel jig, whether store-bought or self-made, will come in handy for the project. 

A plastic block dowel jig for under $10 is an easy purchase; a steel block might set you back $75 but will last as long as your shop does.   A $10 set of dowel centers might be a good shop addition, too.  And a bag of 400 assorted size dowels, again a $10 purchase, will last for many projects.