Making A Custom Form Tool

Copyright 2009 by James P. Riser




For a special project that I wanted to make, I decided to use a custom form tool for the machining. Basically form tools are made in two types: dovetail or straight and circular. I chose to use a circular type for ease of making.

The advantage of form tools is that they may be resharpened repeatedly without altering the desired contours of the tool.

This web page documents how I made one form tool to be used on my small turret lathe - shown below.

It all began with cutting off a length of O-1 tool steel 2" in diameter.


The blanks and the collet used for turning.


The blank of 2" tool steel is first drilled then bored to the required size for a tight fit.



The blank was next slid onto the tool holder bolt.


After mounting this assembly in my Sheldon lathe, the form cutter was turned to shape.




This is the tool after turning.


It gets held in this form tool holder.


The holes are for positioning an index pin in the cutter. The cutter was marked for drilling.



The hole for the index pin was drilled next.


The cutter was marked for grinding.


The grinding was done on my surface grinder.



The heat treating oven and tongs.


The oil for quenching.


The toaster oven preheated for tempering.


Heat treating was done in the oven with no control of the atmosphere.


Oxide formed on the cutting tool.


The oxide built up rather thick.


After soaking, the cutter was quenched in the oil.


Most of the oxide flaked off as soon as the red hot steel hit the oil.



The cutter was next tempered in the toaster oven.



The tool after tempering.


The residule scale was removed with a green scouring pad.


The final grind (sharpening) was again done on the surface grinder.



The finished tool after sharpening and cleaning.


The tool ready to mount (index pin has been installed).


The completed form cutter mounted on the holder.


The cutter angle is fine tuned with a screw driver.


The cutter in use on a 1" brass bar.


Cutting off on the turret lathe.



The last step was to engrave the finished weight.



The completed weight.


The form tool size and shape allow making identical weights as required.