DRO for 6X26 Benchtop Knee Mill

DRO on Benchtop Knee Mill

X axis Scale

X-axis Close-up

Y-Axis

Z Axis

X, Y, & Z Axis

A shot of the completed installation. The DRO components were purchased from the eBay store of Shars Tool. The cost was less than $350.

A 450 mm scale ($67.90) was chosen for the X-axis. The table stops were removed and the fasteners for the stops were used to attach the scale to the table. A length of 3/4" x 3/4" aluminum angle was placed behind the scale brackets before they were tightened. The angel serves as a chip shield. I discovered that the accuracy of the scales could be affected if the sensor had any strain placed on it, while it traversed the scale. I settled on using pieces of 26 ga. aluminum sheet to attach the sensor to the table ways. The thin sheet is rigid in the X direction while still being able to flex in the Y direction. To allow clearance for the scale brackets at the ends of the table travel, the caps on the oiling cups had to be removed and replaced with a removable plug. Aside from that modification, no other changes were made to the mill for the X-axis install.

A close up of the X-axis as it nears the right limit of it's travel.

The Y-axis mount required a bit of drilling, tapping, and other modification; including the removal of the adjustable Y-axis stops and rail. Two small holes were drilled and tapped in the knee to allow for the attachment of the 8" scale ($24.90). Again, light gauge aluminum sheet was used to attach the sensor to the underside of the table way bracket. A neodymium magnet and plate that was salvaged from an old computer hard disk was tapped to accept screws to attach the sheet metal and the magnet was attached to the table way. The switch box also had to be lowered about an inch, to allow clearance for the scale.

A 12" scale ($37.90) was chosen for the Z-axis. One hole was drilled and tapped to support the scale near the bottom of the column. An angle bracket was formed from one of the included brackets to support the top of the scale. Two holes were drilled in it and corresponding holes were drilled and tapped in the mill column, to attach the bracket that supports the top end of the scale. Light gauge sheet metal was used to attach the sensor to another magnet that attaches to the knee.

Close-up of all three axis installed and ready for use. The three axis digital display was the single most expensive component of the system ($189.95). It included a power supply and three 6' cords to attach the scales to the display. The display unit has a magnetic back. I fashioned a mounting arm from 1/2" steel pipe and a length of 1/2" rod that telescopes inside the pipe. The mounting plate for the display is formed from 14 ga. steel sheet.