Track frames

These brackets were fabricated from mild steel and silver soldered from two components, one turned the other a CNC profile. The brackets hold the idler wheel axles.

The channels are made by stick welding two pieces of angle after it has been machined to make the channel 36 mm deep.

A piece of aluminium was used as a heat sink to weld on the inside first, both angles were clamped firmly.This resulted in a good penetration weld.


A weld was then run on the outside, this weld was ground off and filed flat. The resulting channel although badly warped was clamped flat on the mill table and surplus weld machined off.
The resulting channel was then straightened in a press.

The track frame pivot was fabricated from mild steel and silver soldered.

Idler wheel

Idler & sliding axle blocks (fabricated from mild steel silver soldered).
Idler 147 mm in diameter.
CNC machining time 12 hours with 6 mm 2 flute end mill coated carbide at 5000 rpm feed rate 255 mm per min.








Final two segments to be machined. Note large holes to drain away swarf & suds.

Assembled Track

Here is the drive sprocket in the track. Every second tooth engages a pin. When handling the track now, gloves need to be worn, it pinches the skin readily otherwise.

Sitting on the bench with the drive sprocket and idler blank.

Idler Wheel - Machining

Mach3 two thirds through machining the idler wheel.

The partially turned billet. This will need to be turned down to the thickness of the ribs so the ribs can be milled.

Two photos of the idler wheel mounted on the mill. The job was paused to take the photos. Note the starting holes from the original drawing and the cut made on the lathe prior to milling.

Idler Wheel - Drawings

The Idler wheel drawn in AutoCAD.

Notice the five holes marking the pilot holes to rough the spokes out.

The ribs exported into SheetCam to set all the parameters such as tool path, tool speed and depth. These instructions are exported to Mach3.

The remainder of the spokes will be imported as a separate layer and cut out in a separate operation.

Now imported into Mach3, this shows the toolpath for each rib ready for machining.

Drive Sprocket - Machined

This sprocket requires both X and Y axis to have 200 mm travel which is more than the 180mm travel of my mill.

The blank was mounted on a rotary table so that three teeth were machined.

The blank was rotated 40 degrees and the machine code 9 times to give 27 teeth.
The profile on the inside of the teeth was done the same way.
All the spokes and the fluting were cut as one
operation without using the rotary table.

There is one drive sprocket per side. They are each machined from a single billet of steel. First the billet was turned on a lathe to thickness the spokes and finally the teeth and spokes were cut on the mill.

Drive Sprocket - Drawing

This is the drive sprocket after it has been imported into SheetCam as a DXF file from AutoCAD.

There are 27 teeth. Pitch between every second tooth is 40mm.
OD is 185mm.

Tracks - Assembled

Here is the assembled track. A left-hand and right-hand link show how they fit into the track.

Each pin is a press fit. You can see the nuts which hold the grousers to the links.

Tracks - Grousers

The grousers were cut from I-beam and detailed on the mill. They were shot blasted to remove the rough edges and give a cast/used appearance.

The grousers are bolted to a pair of links with four bolts.









Partially machined grousers,
Machined 70 plates ,66 required

Tracks - Machined Link

Left and right completed links.
Bushes are 12mm dia. of 4140 steel.
Pins are 8.3 mm dia. of high carbon steel.

The pitch of the links is 40mm.














A link mounted to the mill having just been profiled.









Profiled links.









Each track contains 33 left and 33 right links. In total 140 links were machined. Here they are partially machined.

Tracks - Link Drawing

First the track link was drawn in AutoCAD. This shows the toolpath to cut the profile. It does not show all of the operations required for a finished link. There are seven processes in total. This drawing is in SheetCam and the G-codes will be posted to Mach 3.

Machining was performed on a Nicols mill converted to CNC using servos and driven by Rutex drivers.

Getting Started

Here is the photo that was the inspiration for the project. Copies of the service and parts manuals were obtained as references. Some drawings are printed in these publications. Other sources of detail came from photographs and actual measurements from the full size Sixty.