3D Printed Change Gears for the Harrison M250 Lathe

I am the proud owner and user of a Harrison M250 lathe. I have a full set of metric change gears, but like most I lack those required to cut imperial threads.

This wasn't a huge drawback for me until I decided to restore a 1919 Drummond B type lathe. Suddenly I needed to create Whitworth threads.

I quickly realised that the change gears for Harrison M series lathes, either metric or imperial, are like hen's teeth. Looking into manufacturing my own, the major stumbling block was seen to be the production of the elegant but over engineered 6 point drive spline.

3D printing was the answer. This allowed production of change gears to precise dimensions in a resilient material.

Here is a photograph of a 40 tooth and a 44 tooth M series change gear as 3D printed:-

As can be seen, the spline is reproduced faithfully, as is the correct tooth form. 

This next photograph shows the 40 tooth gear in place in on my M250, in change gear train "F":-

The gears are printed in a tough resin, using a highly accurate Formlabs machine. The following material mechanical properties are taken from the Formlabs datasheet:-

Tensile Strength - 52.2 MPa

Young's Modulus - 2.24 GPa

Impact strength (Notched Izod) - 51.1 J/m

Full sets of imperial and metric change wheels will shortly be in full production. Gears can also be made for other machines where spares are hard to come by. For example, a tumbler set for an Emco lathe is currently at the design stage.

If you require change wheels for your Harrison M series machine, or you have a gear requirement for another manufacturers machine, please get in touch at the email address below:-

wilsonreactionresearch@yahoo.co.uk