Square Peg Round Hole

Square Peg Round Hole or turning a square section part in a 3 jaw self-centering chuck. Having seen this on so many instagram and pinterest posts I thought I should have a go. The thing is I needed a way of drilling a 6mm hole through a piece of square section oak. The independent 4-jaw chuck felt like an overkill.

A piece of plastic pipe cut to around 50mm long and then with a slit down it’s length and a section removed was easy to find. It was slightly bigger diameter than the square piece of oak. Probably around a 1mm gap around the oak when it was in the pipe.

square peg round hole

The pipe was gripped in the 3 jaw chuck of the Warco WM240B and tighten, whilst being careful not to overtighten and deform.

drilled piece of oak with outer plastic pipe

I centred drilled, then drilled with a 4mm drill bit before finally taking the hole out to 1/4″ in diameter.

I turned the part around and repeated the drilling process.

Take your time and you will get a better result.

These oak blocks have brass axles fitted to them and then the wheels slide onto the brass axles.

whippet engine on wheels

Next, I needed some brass nuts to hold the wheels in place.

square brass held in tube

I decided to make square nuts using 5/16″ square brass rod.

Again held in a piece of tube, this time a piece of steel tube and held in the 3-jaw of the Hobbymat MD65.

checking accuracy of drilling square tube

I drilled a 5mm diameter hole through the square in preparation for tapping it 6×0.75mm.

Just checking the wall thickness and it is 1.47mm and the variation around the square is ~0.04mm which is roughly +/-1.5 thou in old money. This worked out very well I think.

brass square nuts

The square nuts fitted to the brass axle that runs through a square oak outer axle.

A tube with a slit to hold square material in a 3-jaw self-centering chuck works very well.

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