CQ9325 10 x 18" (250x450mm) Bench Lathe

Carriage handwheel fix

modified handwheel

The only way to eliminate the annoying wobble in the handwheel is to extend the hand wheel shaft from the face of the pinion gear back towards the leadscrew.

This allows an additional locating bush to be fitted.  This bush is retained by a metal block attached to the inside left of the carriage body.

The handwheel shaft is now effectively located across a much wider plane, with a bush each side of the pinion gear.   No more wobble.

To do this, I first drilled into the gear face about 5 mm, turned up a shaft to fit (10 mm diameter), and hard bronze brazed it into position.

This was then turned down to the internal dimension of a bronze bush to be used (8 mm), and fine finished.

Next I fly cut a rectangular block from heavy steel plate, to fit inside the carriage.

The carriage was drilled to accept two Allen bolts which retain the block in position.   The top one is 8 mm, the bottom 6 mm, to clear the leadscrew cover - you could use two 6 mm.

The steel block was then drilled, tapped, and bolted into position.

For this type of job, it is necessary to drill the hole for the shaft extension with everything firmly bolted in place, as any misalignment will cause the shaft to bind.

To do this accurately I turned up a drill jig (guide) to fit inside the original cast iron bush.

With the cast bush and jig in position, I drilled an 8 mm pilot hole through the steel block - making sure not to damage the leadscrew.

I then bored the jig out to the external diameter of the bronze bush to be fitted (12 mm) - leaving about 1 mm wall thickness - see below.

drill jig

The full sized hole for the bush was then drilled through the block,  again using the jig.

I removed the steel block from the carriage, turned up the bronze bush, and firmly press fit it into position.  The bush could be pinned into place, but it's unlikely to move.

The completed parts are seen below.  As the block is hidden from view, a few machine marks won't matter.

The steel block was then bolted back into the carriage.

The extension on the handwheel gear shaft was measured for clearance and cut to final length.

Everything was greased, and the shaft and components refitted.

The shaft and bushes lined up perfectly, everything sliding smoothly into place.

Above is a shot inside the carriage - showing the finished job and clearances.   The bush is wider than the metal block, to provide maximum support.

The only obvious changes after the modification are the two Allen bolt heads visible above.

This modification is designed for a standard CQ9325. 

The "A" power cross feed model appears to have less space available, as a worm gear is situated on the leadscrew behind the handwheel pinion gear - if anyone has done the modification on that model, I would be interested to hear from them.

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South Australia