Lathe Cutting Tool Height Gage

[Paul Jones]

This lathe cutting tool height gage is based on a design by Hardinge but with the addition of a rectangular base for extending the gage past the edge of a lathe cross slide housing for easy access to the cutting tool. This tool provides a convenient way for setting the correct cutting tool height without the need of first setting steel parallels spanning the carriage aprons to set the height gage. The distance from the top of the lathe cross slide to the center line of the lathe spindle is 3.460” for my 12” swing geared-head lathe. In addition, this height gage has a pair of rare earth magnets embedded in the base that allow the gage to easily extend over the top edge of the lathe cross slide.

The gage is made from 1.1” dia. cast iron round stock and 1.5”x2.5”x0.5” 6061-T5 aluminum. The top surface and bottom surface were machined using the gage cylinder as a mandrel to ensure the base was perpendicular to the height gage body. The Hardinge tool design allows over and under cutting tool touch-off by using a thin cylindrical part that pivots from the top of the cylindrical body (which is 3.460” tall). Two recessed rare earth magnets keep the gage firmly seated on cast iron cross slide. I should have drilled the 10-32 thread hole before parting the thin cylinder part but did not do this step in the right order so instead I used a small hose clamp to ensure the separate parts were aligned during the drilling.

The gage base has a sliding fit and held in place with two 8-32 set screws placed on opposite sides of the aluminum base. A Cogsdill Burraway tool (an eBay buy) was used manually to deburr the threaded holes to ensure a smooth sliding fit of the tool height cylinder. The two side set screws allow minor height adjustments. A future improvement may be to add another 0.375” dia. x 0.188 thick rare earth magnet in between the existing magnets and/or lengthen the 2.5” aluminum based to ensure sufficient extension over the cross slide edge.