A Homemade Set of C-Spanners

This is a fairly quick and simple project that requires very few tools to make.

I need to upgrade the spindle bearings in my Chinese mini lathe. There are two 36mm locking nuts at the rear end of the spindle that require a pair of C-spanners (or a C-wrench to some) to remove and reset when putting them back. I could use a pair of adjustable plumbers pliers that I have but I don't like using them as they tend to leave teeth marks in the nuts.

I looked online for these c-spanners and the best price I could find was around $AU34.00 each on eBay from Sydney and the cheaper options were all from China. Being in this lockdown state from the corona virus getting anything from China is going to take a long time.

So why not make a pair of them? And, that's what I have done.

High accuracy is not very important for the use I'm putting them to - as long as they fit over the nut and sit correctly on the notches around the nuts they will work fine.

Why do I need a pair of them? Well, when the new bearings are fitted the nuts need to clamp the spindle in the headstock without tightening it up too much, and the second nut is then tightened against the first nut to lock it in position.

2 lengths of flat steel bar - 5mm x 30mm x approx 250mm (or to suit your need)

Tools needed:

Angle grinder with a 1mm thick cut-off blade (a bandsaw if you are fortunate to have one)

A pair of dividers (or compass)

A drill and metal drill bits

A bench grinder

Metal files (half round, and flat) and emery paper etc for finishing

Mark Out

In my case, the nut is 36mm in diameter so we'll need to scribe a half-circle of 18mm from the one edge of the bar. Leave around 10mm at the end of the bar. I punched a small hole for the dividers to rotate in and to show me where the other lines need to be drawn from.

Sorry guys - I don't have markout blue. I tried to use a black sharpie but when I scribed the lines the dried ink around the lines shattered and made a ragged mess of a drawing. - So I cleaned off the ink and just scribed directly on the metal.

Measure the width of the notches in the nut (around 4mm in my case). This will determine the size of the hook on the spanner end.

Scribe a line from the half-circle centre out towards the end at approximately 30 degrees. I used a small gauge that I have to do this.

Now scribe the outline of the hook.

I then scribed an inner half-circle to give me a reference point to drill holes to ease the cutting out of the half circle.

Punch points along the inner line and drill them through

Cut the half-circle out using the angle grinder and cut-off wheel leaving a jagged edge to be cleaned up. The cut-off wheel will not easily get in to cut away the metal at the back of the hook. This will be filed out and cleaned up with a half-round file.

Using the bench grinder the lower trailing edge can be rounded out. This allows the c-spanner fit a variety of nut sizes a few millimetre smaller or bigger than the 36mm of my nut, and it helps in hooking into the notch easily.

There's not much more to do now.

Clean up

All that's left to do is to file/grind down all the rough edges with whatever tools you have. I used a half round file with a flat back and the bench grinder. I drilled a hole in the back end of the tools too so they could be hung up

I took off all the black layer on the steel as it gets your hands really dirty handling the tool. To do this I used my orbital sander with 80 grit paper and an emery flapper wheel held in the drill press chuck. Some rough spots I ground off using the angle grinder and a ceramic cutting wheel (using it flat along the metal surface).

I think what I might still do is to treat the steel to prevent it from rusting by heating them up to red-hot and dropping them into oil. I believe this is a good method of protection.

Hope this is helpful to someone.

Enjoy making your own tools.